Thank you for teaching us as you learn these things yourself. I have learned so much from your videos! There is so much to learn and you are so good at explaining the key points from your testing. Your channel is the best I have seen to truly make the complicated simple to grasp and you do it with great music and personality!!
Hey! Tried this and it works! My batteries have a complex installation and I really didn't want to take them out of place for servicing. I achieved balanced cells merely by lowering the overvoltage cutoff to 3.45v as you suggested and voila! Thanks!
Your explanation of absorption was great, it really helped to visualize that part of the charging process! Where people can visually see there's still so much energy that can be packed into the battery even when you've reached the right voltage. I've explained absorption before to people that it's like filling a cereal box. You can quickly fill it up to the brim but still not reach the gross weight of a full box until you kind of shake the box and let it settle some. Then you can pour in more. It isn't until you reach the right weight that you can consider the box "full" or "saturated". (The height would be the voltage, while the weight would be the current.) So the "absorption" phase is kind of like shaking the box while you pour in more cereal. No need to put up the footage from the past 3 days if you feel this video sufficiently explains/educates people on what you learned. It's a wash of whether that could be helpful - on the one hand, people will see the entire process of how you were troubleshooting and learn along with you, but on the other hand it could actually complicate and confuse the message of what ultimately needs to be learned. With the deluge of information people face these days, I tend to think keeping things simple is better, that the value of watching you troubleshoot is negligible since you explained your thinking process pretty well here. So if you're comfortable that there's little to be gained from your footage from the past 3 days, I'd say "spare yourself the effort (and potential embarrassment 😆).
Your cereal box analogy is pretty good but it tends to apply more to flooded lead acid. In the case of lifepo4 that extra energy you're pushing in to the battery is done by fixing the voltage so that the battery cells that are already fully charged cannot accept any more because they resist this voltage but the battery cells that have not caught up yet can accept this voltage. In bulk you were charging based on fixed current but now you're charging fixed voltage. This means that the individual cells that are lower in charge are now going to be able to catch up to the ones that are already charged fully. Why don't the more fully charged cells also continue to take a charge and end up over charging during this absorbtion stage you may ask? Because you are now keeping voltage fixed and any cell that's fully charged will resist and push back against this voltage. The only way to make them charge more fully would be to increase the voltage. Why didn't the lower cells take more charge during bulk you ask? Because there are always slight variations between battery cells resistances. So why can the lower charged cells accept a charge now when they didn't before? The answer is they did, but they just did so at a slower pace.. now you are giving them time to absorb this continous constant voltage over time and bring them up to the same threshold as the other cells at which point they will also start to push back against the voltage. Think of it like teaching a class of students that vary in intelligence. The bright kids catch on quick and then sit there already educated but learning nothing new whilst you continuously repeat the same information over time untill the slow kids catch up. This repetition of information is analogous to the repetition of applied voltage over time or absorb stage as we call it.
Huh, 3 years later bought my first LiFePo 4 Cells. I was so busy to put the box together, and forget balancing 16 cells in parallel. I measured the resistance of each cell and there were no big difference. On the end, the BMS had problems with one cell, which always hit the top voltage at first. So I decided to disassemble the whole pack and start from scratch. I didn't even have a charger for 3.6 Volt, but remembered, I have the same buck converter as you show. It is now two days charging up to 3.6 Volt. Now seen your video, o ha, ooh, damn, good, fucking great, now I understand about charging voltage, absorption, and how to handle my 320AH battery pack. Thanks a million. 👌😎
Hi Andy. I will give you my opinion. I made a battery with 22 LiFePo4 cells and installed without BMS on a scooter. 2 years after almost daily use I don't see any imbalance. After much reading and watching videos of experts, I opted for the technique of bottom balancing instead of top balancing. The explanation is simple. All cells have a common minimum, but not all can have the same maximum. I unloaded cell by cell until its minimum tension and left it to rest for 2 days (the tension will naturally rise a little, being necessary to repeat). With all the cells equal at the minimum voltage, I connected them in series and connected the charger until it reached 80% of the maximum capacity. It is my safety margin and I guarantee that all cells are able to balance themselves at this voltage. LiFePo4 chemistry is very stable. It's just my opinion. Good job Andy.
Thanks for sharing. Interesting approach indeed...This method will work as you only charge to 80% capacity, that's correct. How far down do you discharge the cells during operation?
You rotten sod rubbing it in about your lovely weather and how we are freezing and your going in the pool to cool down ! Great episode as always. Lovely to see your frog at the end.... kept thinking of them when I saw your green battery indicator on your phone. Learnt a lot from your channel. Thanks
Dear Andy, love your humor and most practical demo of solar system building. Just went back to watch your first episode from very beginning. Love it and enjoy it.👍
You been my teacher and I've learned a lot from you.. I'm using sealed wet cell and I know If I took my batteries and disconnect from my system, the solar power of 1000 watts would just take over and maintain my 12 volt / 1000 watts requirement. I really think you very close on solving this.. I live in sunny southern California and my generation has been excellent. If you can master using your batteries banks with the solar system and normal load usages at the same time, then I will upgrade to lithium lifepo4. Thank you for teaching us !!
I had similar issues, and what worked for me was this: Charge the pack until one cell peaks. I used an 8S charger and did 8 at a time so I could see which cells were topped out at 3.65V, and which were lower. Then individually charge any cell that wasn't topped out. Then charge the pack again as an 8S pack to see which cells were still not peaking, then I charged those independently again, and after 3 rounds of that, all were very well top balanced. You can charge the individual cells with a charger while still in the pack by just using alligator clips for the individual cell. I use a battery charger for the independent cell charging because it measures the AH added, and it shuts down by itself so I don't have to watch it. Balancers are only for maintenance, you are definitely right on that. You must balance the cells before you can even think about using a balancer, BMS balancers only work when batteries are very close to each other for state of charge. When I had one cell peaking in the 8S banks, the other batteries were anywhere from 6 amp ours, to 84 amp hours lower! I came to the conclusion that adding to the low cells was way more efficient than discharging the high cells, as that is how I started but quickly realized it was a flawed approach.
Wery interesting! Can you explain, what does it mean? I have all the time same three cells, that are higher then others for around 0.010- 0.035 mv when charging, especially higer then 3,5v and in some time after stop charging their voltege goes lower on 0.020- 0.040mv then othe cells. And balencer begins to charge them. I did paralel topbalance befor assemble. I use Daly bms and Neey 4A smart active balancer. I see that during the end of charging, that 3 cells runs up, balencer discharge them, deviation voltage goes from 0.050mv to 0,004mv, charge stops, and after that, when bettery goes in rest, voltege goes down, and that 3 cells become lower than others... They goes much lower ( near 0.080mv) under load 60-90A. Without load, they also steel lower. I set balancer to continue balance after charging to rest to until 3,330v and usually get 0.010 mv diff. But in this case next charging shows bigger then 0.040 mv different, becose other cells gets some deviation between one another. Maybe that is normal behavior? Maybe, I have to charge battary to 3.65v per cell, and then charge that 3 cells individualy with 3,65 v automatic Lifepo4 charger?
Just watched this video. Experiencing the same problem on my golf cart project. I have a 135A 14s LiNMC battery with a JK BMS, a 300W solar panel roof, a Victron 100 20 MPPT, and a Victron 712. Massive amounts of sunshine here in So. California. Trying to keep the solar power system from triggering the BMS. This video has gone along way to help me understand the MPPT settings. Thanks...
Great insights there. Thanks for sharing with us! You learn when you jump in the deep end - if you were mucking around with cheaper, lower capacity or fewer cells, you wouldn't worry about these subtleties as much.
Just wanted to say thank you for showing us the whole process as you learn about charging. I am building a 12v LifePo4 battery right now and am in the same situation and find it all confusing about what settings to use, but watching these video's has helped a lot!
LifePO4 really prefers to take all you can give it. the float charge is for lead-acid batteries. and the absorb is also for lead-acid batties. it wants the bulk charge. that why they disable or have to reprogram the mppt chargers as they are not designed for LiFePO4. study up and you will find the correct information.
I think this was one of the best episodes for learning and conecting things in my brain ! when i test lead acid batterys i have this system, i charge and leave on float for 3 days to let all the energy absorb, i stop the charge then i test the voltage after an hour and then after 24 hours another voltage test and a 50A load test and then i choose the batterys closest to each other to put in a battery bank for solar, it's just the way i do things after years of charging used batterys and resurecting them for solar powerbank use but after watching this vid it clicked, somone else has similar thoughts ! differant chemistry i know but cool to see a similar thought process in somone elses head !I really really enjoyed that one, i love learning alongside you ! keep it up :)
Thanks for the feedback. I've got this effect all the time and step by step things make starting sense... Then I need to test and confirm that new learned, so it all takes time...
I only found your channel recently. I love the correction you made to your graph at 8:25. LiFePO4 batteries charge with a phase-change reaction, so their voltage is fairly stable through much of the charge/discharge cycle. You can DIY a quick and easy charger by combining a CC circuit with a CV circuit, which is essentially what you did. For a small cell (AA sized) application, I used a LM317 linear voltage regulator paired in series with a mosfet as a linear current regulator. Worked like a charm.
hi ANDY there are many teachers in this world, but very view can explain a process that everybody can understand it. u are one of the view exceptions to make ur presentation clear. it was the first time i see the total picture of charging a lifepo4 battery. thank u great job. i am the German guy in Texas and just started up my 30 kw system with a 8 kw solar system. i am using a SOL ARK grid tie inverter that can start a back up generator in case the grid goes down. i will make a you-tube movie the next few month and will send the link to you. again thanks for all the patience and smarts you have. viel glück Jan
Excellent detective work there... It's even harder to build an understanding when you have experience that needs to be forgotten because it no longer applies. It would be interesting to see what the settled voltages of each cell were, after you carefully saturated each one. Perhaps they each have a different saturation voltage... This would explain why the voltage based balancers can cause trouble!
This is helping me with my battery so much. Thank you youtube algorithm for leading me to these videos because I have the same bms. I have been having lots of trouble balancing. Before I was trying to balance during charging. I will take the battery to 4.1V/cell average (LMC not LiFePO4) and then balance after because the 200ma balance is so low even for my 68ah battery. Thank you!
Andy please don't annoy me with the wonderful weather. I have been digging out my panels from inches deep for the last week to be able to charge my batteries. This video is the most informative you had made so far. I will pass you from amateur to pro battery builder with a B+ You still need the 10A battery equalizer to help with the lifepo4 algorithm.
Put some voltage on these panels so the snow melts! I'm probably only a C+ at the moment but came a long way... NOOOO, no balancer or equalizer. They will just hide the problem. Once I found the issue, maybe, but for now, I need to dig deeper....
@@OffGridGarageAustralia I need more info about the voltage I need to put in the panels. When is freezing rain I have to spend hours scraping the panels.
Great Video. I've been experimenting with a Growatt 3000K 24v 8S 3.2 cells. And It is very confusing to get all the parameters rights. Your video has clear many questions regarding CC/CV, voltages and amps. I am still playing around but I think I have found a sweet spot for my setup. Thank you very much for sharing.
Your frustrations make life easy for the rest of us. 🤣. Thanks for your videos. Very informative. In Southern California its sunny always.....until I start experimenting with my solar. ⛅☀️
Thanks Kevin, happy to share everything I find. I know what you mean, there are always clouds in exactly my area when I want to test something. Blue sky all around but this one cloud ⛅
Exactly, its the same when you need to really equalise a big battery like an electric motorcycle, you charge with a low current to let the BMS do his job, thanks for the clear explanation 👍
Very insightful, excellent material to ponder. You have hit on an issue that I have been thinking about too. The longevity of the the batteries is greatly diminished by charging to 100%. a combination of voltage and current monitoring must be the answer. The tolerances are so tight as you point out it's so difficult to get it just right. Keep up the good work. Perhaps keep a log of the batteries that are always the highest and lowest to see if their performance deteriorates faster than the others. Keep testing to find the sweet spot! Thanks for your video
Hey, Andy! Great video! The problems that are the most difficult are also the ones that will teach you the most. You already made great progress and learned a lot. I have no doubt you will find the settings for the charge controller and bms that work for what you want. Good luck my friend.
Why not set float voltage to be the same as the absorption voltage? This will allow the BMS to continuously balance cells as well as allow solar to supply any loads without having to cycle back to bulk and absorption mode again
@@OffGridGarageAustralia yeaHHHH waiting for this Video from Spain and ready to get all hardware to copy your experience! we have a lot of sunny days as well in this country.
No, never do this (see my detailed answer elsewhere). Batteries are not capacitors, even if the amps are reading zero there are going to be eddy currents at the potential wall and overcharging above it if the charge controller is left in that state. Setting the float high enough to actually get the BMS to top-balance the cells is also high enough to overcharge the battery or greatly reduce its cycle life. You want the charge controller to charge the battery high enough for the BMS to be able to top-balance it (e.g. bulk/absorp target minimum 3.45V/cell. 3.5V/cell is better with the absorption time set to 0), and then for both the charge controller and the BMS to both stop messing with the battery until the next charge cycle (e.g. float setting should be no higher than 3.35V or so). -Matt
you're the best ! I literally want to go to Australia specifically to hangout with you 😊. I enjoy learning with you and appreciate your fun attitude to figuring out problems 👍 By the way I am in the middle of this exact issue you encountered here . Just did a single cell to 3.5v taper to < 0.1amp for each cell..I then paralled em and did the same thing. Waiting for some load testing equipment to re-test. Fingers crossed
Thanks so much!! I have learned more from this and your next video than I have learned from tens of hours of solar/charger/battery videos over the last year or so
Fantastic Video. I got lost in exactly the same trouble 1,5 Years later with my cells and that video was THE EYE-OPENER. Where the hell did you get these module FOR FREE in 2021???
You're getting so good at these videos! It's very accurate what you mentioned about every system being individual too. It's the reason I get frustrated at "kits" being sold online with the expectation that you connect A-B C-D etc,and it works, when it's much more detailed than that, at least to get good solid performance, that lasts like it should. I reviewed a battery kit from a local supplier last week, and found that it was quite easy to balance the cells by leaving the (Lab Power Supply) charger connected overnight with the current limited to a bit under 100mA. The balancer took care of soaking up the excess power to the high cells. The same goes with my Daly, however I have balancing enabled throughout the entire charge procesas, all the way from 3.0v. It's a Hare and Tortoise type scenario, slow and steady is nearly always best.
You cannot build such a battery from a kit without understanding and testing it afterwards. If you have low capacity cells this method may work but with these 280Ah cells, there is no way the BMS will balance them unless the charger is off and they are already on a high SoC and in the steep part of the curve.
To me it makes since to charge into the upper voltage peak to get out of the flare zone to know all your batteries have absorbed the bulk of there capacity. It also seems that it’s much easier to balance in that upper voltage peak since it drops quickly to the flat region so quickly. Maybe if you raise charge voltage per cell to 3.45 or 3.5 that will allow the batteries lagging behind time to catch-up in bulk mode and give the BMS a little more room to work. The trick as you have shown, at least on the first go, is that it’s a little tricky to get them balanced at first but maybe this will allow them to stay more balanced. I am learning with you and am waiting for my batteries to arrive, so thank you for all your hard work and then sharing it!! I am also considering using solid copper bars between the batteries, 5mm X 19mm X necessary length.
Thanks for your feedback and kind words. I was thinking the same at the beginning and hence I chose to charge to 3.4V as this is already in the steeper area of the curve. But yeah, you're right the higher you go the steeper it gets. The problem is that if you have a lot of solar coming in at this point of time it quickly gets out of control as these cells charge very quickly and go over 3.6V in no time. The charge Controller keeps charging as it only sees the overall voltage but not individual cells. I had this twice now and decided to lower the voltage for that reason. There is still a lot to consider and no right or wrong... just a different :) And that's what I'm doing right now, trying different settings and see what consequences they have.
The BMS will handle any over-charge conditions on individual cells, regardless of what the charge controller is trying to do. But even without a BMS, LiFePO4 cells can tolerate up to 4.2V before the electrolyte starts getting damaged. Nobody ever charges cells above 3.65V so there is actually quite a bit of wiggle room there. You still want a BMS, though, to ensure that no cell is over-volted into damaging territory. If you are finding individual cells going that far out of balance while all the other cells are perfectly fine, then you have mismatched cells and you need to replace the ones that are going out of balance with new cells. Yes, this does mean that now your new cells will not pop-up as much as the older cells (due to less capacity in the older cells), but that's fine if the older cells represent most of your battery bank. It won't hurt anything and it means you can keep using the battery pack without having to wholesale replace it. Its an economic decision... do you replace the whole thing, or do you replace one or two cells? If the number of cells you'd have to replace gets too high, then you replace the whole thing. You still absolutely need a BMS for the short protection, low voltage protection, high voltage protection, and to prevent a meltdown if an individual cell goes too far out of spec. -Matt
One thing that may be happening with your cells since some are newer than others is the potential for some variation between manufacturing batches. Another thing I have noticed with my smaller cylindrical LiFePO4 cells that are all new and from the same batch is that they seem to have a wake-up period of a few cycles after being stored for a while (1-3 months) where they don't pull full capacity and then after being cycled a few times they come back. Not sure why that happens but it seems to be a thing. I wonder if since those batteries have such a large internal surface area, it just takes a long time for them to fully saturate. I have an active balancer on my pack that will balance at 2 amps so I set the float to happen around 2 amps so that the batteries are allowed to balance. I have the balance voltage of the BMS set to 10mv below the setting of the active balancer. When they were out of balance at the beginning I would see balancing happening on the active balancer during bulk and float but now they are usually all fairly well balanced during the absorption stage so the active balancer only comes on when the BMS isn't able to balance which is now fairly rare.
Very true, think of it as if you were filling a drum with foam peanuts. Once full, you tap it a few times more electron settle themselves, and you add more til your full. A good balancer will do this an as you say it takes a few cycles to reach steady state.
I ask the same question why cant you just make the absorb and float the same voltage? I suspect it may have something to do with What Comment is stated on Emily and Clark's channel, but I dont fully yet understand it. """I’m glad you mentioned low current overcharge of LiFePO4. So many people seem to believe that only the charge termination voltage matters, and neglect to notice that the cell manufacturers always stipulate a 0.05C charge termination rate. Charge to that voltage at a lower current and you’re overcharging."""" Reply from Clark """Yes, and that can happen so easily with solar or while using your electrical system during charge. Honestly I didn't understand this as a problem when I started this project. Solving the low current overcharge is what made this interesting to me."""
I did. Btw Andy could you perhaps consider getting a po box that we can send stuff to. I was thinking sending some diffrent dc fuses you could test/dissassemble or just send some random stuff. Anyways really enjoy your channel and your personality. Best regards from northern Sweden.
The full charge voltage is a steep curve, even very slight cell variations will show quite big voltage differences. The remaining capacity of the cells at this point is very small , therefore dont worry about it. When the battery is in a low state of charge, the difference becomes more important as this is more related to differences in cell capacity. I use cells in series parallel to allow cells to be mixed and matched to equalise capacity. Its very easy to over think this, Lifepos really arent all that fussy in real life.
At the end Sparky the Frog, yes!!! Hm, I am little bit confused, I was expecting that 3.55V is already on the steep part of the voltage curve, but maybe because of the huge capacity of your batteries this is also relative. The problem ist that you can not measure the current at a cell level(but I think this is obviouse by now). The question is how to overcome the slightly difference in the charging/discharging behaviour of the cells. I'm afraid that the only way will be, even if you don't want to hear it, sorry for that, the usage of an additional active balancer or to determine the cells with simmilar behaviour and put them together with their own BMSs. Any other ideas?
I think the solution is in not charging to high and let the cells absorb for longer. So I'll do some testing with 3.35V max charge (~95%) and let them absorb until the current is low. I'm freaking out if cell voltages go higher...
@@OffGridGarageAustralia Settle petal, just assume the position & say hummmmm. Get 16 hi/lo volt audible alarms, 1 on each cell & charge/discharge each cell manually with all the spare time you have. I have just ordered an active balancer so I don't have to freak out when my pack is finished. Cheers Scotty
Yes mate you are on your way to be the best BMS, absorption needs time. for me i do not go for the amps but for the volts for 500 volt that is meaning 10 units from 50 A x 50 V that is a total from 160 cells in serie here a BMS is not working.
Wow! This was a year ago. How much change from this to today! This was a big one and glad it came up, one does kind of get stuck thinking most about volts and with lifepo4, current is in ways 1st. This vid would be a good one to do again.
I just ordered two of the JK BMS. Where are these chargers? I have 4 cells peaking at 3.6v while others are as low as 3.1v :( and the heltec balancers aren't working enough. Probably from such a large differential vs only 5 amps of redistribution. Thanks for all you do!
Hi Andy. I could be wrong, but after watching your video up to 3:15, it seems obvious to me that you have at least 3 different connections (2 different busbars and one flexible conductor) connecting the terminals of your cells. I really believe that these variations in conductors between different cells causes that a certain cell charges faster than others and also discharges faster than others. Reason why? I noticed this phenomenon in my own battery, where I had the first four and last four cells connected with standard iron, but between cells 4 and 5 I had a different wire (as you have between cells 7 and 8). Then I wondered what is wrong with cell 5 as it always charges faster and also discharges faster. When I then made the change so that there is a standard iron between all the cells, the problem disappeared. In my view, even a small variation in the resistance of the conductor between the poles makes it impossible to achieve balance.
I have a very simple 4 bar led voltage meter on every parallel cell group. This gives me a rough indication of soc. The way the individual meters behave in relation to each other also gives me a rough idea of state of balance. When the cell voltage is at a point of turning off one of the led bars, at that time I can see how long it takes others to follow suit. The longer the difference between meter states, in relation to each other, the bigger the imbalance. They all light/turn off in unison when well balanced.
For top balancing, I get mine up to 3.7V individually with a RC Charger and then I activate diybms and get them down to 3.55V to have them perfectly top balanced. I made all the experience you've made and it took weeks... :-(. And I fully agree, it doesn't make sense to run cells over 3.35V. There is next to no more capacity and it shows imbalance drastically... even with 800mA balancing current of diybms on my 48V 240Ah you can't manage it. But no active balancer necessary! Having -5°C here in Vienna, my PV made 24 kWh today :-)
Thanks for the info. Weeks, eh.....? OK, I just had my first week of head-scratching experience. Even I worked with batteries and charge controllers before, it's so different. I probably let the cells absorb at 3.35 and call it. Everything above makes me nervous. Gruesse nach Wien!
Hi Andy! I am a novice at all this. But from my research on the internet this is what I have come up with. It is good to do an initial top balance at a very high voltage such as 3.65 per cell. A charge to this voltage will bring the cell to about 95% of its capacity. Even though you don't want your daily usage to go more than 80% as you have said. This is the way to get them balanced in the beginning. Some commenters have said that wants you achieve this initial balance they should stay in pretty close balance afterwards. Because of the flat voltage curve you will never be able to get them balanced if you're only going to 3.5 volts. What do you think? Maybe you could give it a try. Thanks for your videos. I appreciate all your hard work.
CC part of CC + CV charging process makes the charging process faster. Your batteries get charged in a considerably shorter duration. If you have enough time, no need to CC part. Best wishes from Türkiye.
Those little DC to DC buck chargers are ideal to charging your batteries and with individual power supplies, they will do your balancing too, after they have been set-up.
6 месяцев назад
It is a good thing that 2 amp active balancing is built into BMS's now which solves these problems.. Battery construction has also improved..
Hi. One thing that needs to be said and understood. When your battery reaches your target voltage, absorbe begins. The current starts to taper off and will eventually reach minimum current flow. Unless you turn off your charge controller, your voltage will stay constant. Your bms should be equilizing the cells. I am wondering if you bms is a loaded bms or a boost one. (Maybe its both). I suggest that you put your system to work with a load on your inverter. Lights, refrigerator, furnace, or something capable of lowering your battery voltage so your bms can equalize the voltage of the cells. Your BMS works all the time not just when the batteries are fully charged. That way when you get to the top end of your absorb that the voltage of the cells are equally balanced. One thing to consider is did you get the right BMS for your system. You will only know this if the voltage equalizes out properly under normal use.
I do not absorb. I have the absorption voltage to 3.5V and stop charging altogether without any absorption time. Voltage will go back to 3.35V as per float setting in my SCC.
I understand only wanting to go to 3.4v, I would like to charge to that point only too, but you will not get measurable differences in cell in-balance until after 3.4v.
Would it be worthwhile to top balance ~3.65v for maintenance, then dial it back and cap your “daily”charge cycles ~3.5v, to stay in the healthier SOC zone for normal operation? 🤓🤔🤷♂️
I never let my LiFePO4 go over 3.35v each. they still take plenty of current while sitting at 3.28v or higher, and sit there soaking it in for quite a while. It takes several hours for the whole bank to drop down to about 10 watts or so, and they've taken more than 90% of their capacity at that point. I don't have a BMS on them, but they stay within 2mv of each other all the way down to about 2.9 volts, and they come back up evenly. 18S32P heavily used ANR26650M1A that "floats" at 60 volts or runs down to 48 volts.
YES, great to hear my theoretical theory may seem to work well. I still haven't tested it myself but thinking about it all the time to do exactly that. Thanks for your feedback!
You don't really have to do that. If they're reasonably close in voltage, you can assemble the pack and then balance charge it at a moderate current, say, .1 or .2C. The charger's balance circuit will set the cells to the same voltage.
Hi, I also using the Same cells eve 280ah The total battery pack is 48v 560ah Total Solar Power 8 kwp connected to MPPT controllers, My Setting in the Mppt are Bulk : 54.6v Abs time 1h Float : 54.00v Max charging current 140amps This settings Works Fine for me for More than 1 year. And in that time i Never Balanced the Cells again, I think there is also no Need to Balance the Cells every time you charge. To 3.4v
Your float is too high. 53.6V is the highest you should float, otherwise the voltage gets too close to the potential wall of the cells and can cause them to go out of balance as well as cause unnecessary wear. There is no need to fear a high charge target voltage. If you charge to 58.4V the battery banks will still only charge up to around 90%, and still allow the BMS to top-balance the cells (which won't hurt a thing). Charging it over 90% typically requires holding the high charge target voltage for a period of time (i.e. setting a non-zero Absorption time). If you only charge to 54.6V, that is right smack in the middle of the potential wall of the cells. The problem with doing that is that the charge controller will not be able to consistently charge the battery to any sort of percent-capacity. It could wind up charging the battery from a low state up to anywhere between 40% and 60% or so. It will be inconsistent at best. If you are seeing more capacity than that, it's because your float (at 54.0V is too high and essentially trickle-charging the pack continuously or causing extra bulk charge cycles to kick in and do the same thing... trickle-up the battery's charge state). If you really want to conserve cycle life then you don't need to charge the battery all the way up to 58.4V, but you should at least charge it to 55.2V. That will give you a far more consistent charge state and will allow the cells to charge above the potential wall instead of inside the potential wall, resulting in a more even charge across the cells. -Matt
@@junkerzn7312 thanks Matt. As I said in one of my last videos: if absorption voltage and float is to far apart from each other, the MPPT won't supply any power to a load once absorption voltage has been reached and the controller switches to float. It will wait until the voltage drops to float before starting a new cycle. The load will be supplied by then battery in this stage and not from solar as it waits for the battery voltage to drop to float again. I found this is a total waste of energy, the sun is out but the MPPT waits for the float voltage to be reached instead of supplying power to the load and leave the battery charged.
@@OffGridGarageAustralia You don't understand. The battery is STILL ALMOST FULLY CHARGED when it drops to a 3.35V Float. I will repeat that. The battery is still just about fully charged. You aren't saving anything by using a higher float value. Instead, you are reducing the cycle life of the battery. The charge controller will still help supply power to the load and the battery will still remain close to fully charged at a float voltage of 3.35V. I've said this four times now. You aren't understanding the difference between the LiFePO4 charge curve and the LiFePO4 discharge curve. They are different curves. -Matt
I had the same problem with my 12v lifep04 battery installed a 5a active balance board. That's sorted the problem took couple of days but it got the job done. The board was like £10 from AliExpress
This is one of the limitations when all the components in the charge path are from different suppliers. While they all kind of work they are doing this in isolation. The other issue I have with your system is that having loads connected to the inverter will mess with the charge profiles and balancing. As I said earlier I have a MPP-Pip5048GK and 3 modules of Pylontech lithium battery packs. Each pack is 78 amp hours at 48 volt nominal (16 cells) and each pack has its own BMS. Overall the battery BMS talks to the Pip 5048GK charge controller via RS485 and adjust the charge profile independently for each pack as well as the inverter output requirement. So battery charging is completely separated from inverter power output. So the charge settings I have cannot be change as they are set by the battery pack BMS and are as follows. Float voltage 53.2 volts. Bulk charge voltage 53.2 volts. Battery cutoff voltage is 47 volts. In my system the maximum charge current is 80amps. Hope this helps.
Great Videos . I took my cc/CV boost converter and set it for the highest cell then charged the lower cells to match , I'm hopping this will work I think there staying on it long enough to get a saturation but then there's the last cell we matched to and don't no where it was in its charge cycle however this seams to work for me until something better comes along .
BTW, lead acid needs the same absorption, but even more so. Usually if you take the LiFePO4 up to 3.6 and hold it, the current will slope off fairly quickly. Most of the energy is absorbed before about 3.5v and definitely by 3.6v/cell for LiFePO4, while with lead acid it needs to sit right about 2.4v/cell for considerable time. (measure voltage right at the battery terminals - otherwise current and size of connecting wire can distort your readings.) Your quick drop in current at 3.4v/cell is perfect. Float should be pretty close to that, maybe 3.35v/cell minimum. Battleborn batteries has a lot of short videos, and some about the "absorption" needed.
Yeah, we could see this in the video when it switched to Absorption and the current went down from 18A quickly. I'll have a look at their videos, thanks.
I built a 4s pack, and when I first got the cells, I found one which was low and charged it separately for a while. Big mistake. Because I had added several AH to it compared to the other cells, it was always high and the pack cut out before the others balanced. Even with a 1A balancer board, it would start balancing... and then cut out, charger would shut off and I'd have to manually restart it. What I ended up doing was taking a small 5A adjustable power supply, and setting it to 14.0/14.1V. Enough to keep the per-cell voltage above the 3.4V needed for balancing, but not high enough that the highest cell would hit 3.65V and cut out. Left it that way for 24 hours as (effectively) the balancer board kept balancing as the supply kept it topped up. Now, it's all nicely balanced, and I disconnected the balancer board and haven't needed it since.
Is there a reason you couldn't hook the battries up in parallel (assuming they are all nearly the same voltage) and let higher voltage batteries charge the lower voltage batteries? then when they are all the same hook them back up to your system in series?
Hey Andy! Love your vids but have a question: What if i had a server power supply(whith the over/under voltage protection disabled) that outputs 14,2V@No Load, would it also taper the current when reaching 14,2V? My thoughts is that it will because the current tapers because of the battery inner resistance increases at the end of the charge cycle all according to Ohms law?
It will burn out as it won't control the current. Such power supplies don't have a current limiter and connecting a battery is like a short for it. It will try to deliver as much current as it can until something goes off in smoke. I tried with a computer power supply and had this 😉🚬
Hi Andy, great job from you as always. Can i kindly ask for your help. I use BMS JBD AP21S001 and facing problem with drying of my LiFePo4 battery during nigh when my inverter (Axpert King II) are in bypass mode. In application (blue small elefant logo from Xiaoxiang) i see 0,8A consumption every 2-3 seconds. Look like BMS is doing something and finally drying my battery a lot. Can you guide me what to check and how to adjust BMS option accordingly? Many thanks and have a nice day. B.R.
I think I read you note... Absorb 54.4... Float was what I would expect... so, shouldn't Absorb be about 57.6v or slightly more? What have you set your time after reaching Absorb before entering float? After listening to the entire post, I heard you say "two hours". I have never understood what Absorb time should be for LFP and have seen many folks use as little as 10 minutes. Thanks
Hallo: Dank deiner Videos habe ich mich inspirieren lassen auch eine LiFePo4 Batterie zu bauen! 8 Zellen 280AH! Genau dieses Thema hat mich auch zum nachdenken gebracht! Ich werde probieren die Obergrenze der Spannung auf 3.65 im BMS zu stellen und den Laderegler die Erhaltungsladung und Normale Max Ladungsspannung auf 3.4 x 8 zu stellen! Dabei sollten sich die Zellen ausbalancieren können solange der Unterschied der Zellen nicht 0,25V überschreiten! Schöne Grüße aus Österreich!
In order to top balance you need to be charging at no more than 200ma. So that the balancing circuit can eliminate charging on the highest voltage cell(s) while allowing the rest to charge. With 280AH cells the balancing will take forever.
9-12 in of snow yesterday. Had to shovel for the first time this season. More Monday, but may warm up well above freezing enough to melt it down, at least enough to clear the roads.
Great video! I'm a believer too! Sometimes, I feel like a solar monkey... Thanks for sharing all your trials and tribulations. The experiences and the data - all very helpful. I downloaded the newest XiaoXiang app - Thanks! The Play store only has 1014. Battery balancing is indeed a daunting task. I'm still looking for the sweet-spot where it can all run unmanned. I only have 8 cells in a 2P, 4S, 12V configuration.
Thanks for sharing, Peter. I will probably only charge to 3.35V eventually to stay save and don't charge the cells too high. The balancing and testing takes a long time but that's where I learn the most.
Sorry if I'm confused. But did you come to a final result about how to get these batteries even and all charged up? Is there a summary what to do? I have pretty much the exact same setup as you as far as batteries go I just need to get the other stuff. Looks like BMS is first to be safe. Then Charge Controller and panels. Just finishing assembling a cc, cv, 12A 60V power supply, so geting ready to finally unbox and charge them. In Southern California I will get (a bunch of) PV and an MPPT SCC for PV charging. But I've heard initial charging can avoid many of the issues with them (dis)charging at different rates. I've heard a lot about voltage charging first and then amperage charging at the end. Also some info about letting them rest and then topping them off. So.. did you finally come up with a process for yours or does it change a lot depending on the Sun or what? Love your videos love your attitude thanks for the info.
Thanks Steve. You probably hear and read a lot about this stuff. So, the common sense in this is to top balance the cells before building the battery. All in parallel and slow charge to 3.6V, then let them sit until the current goes to almost 0.
I have learnt a lot about solar batteries from your videos. Im building a 8s , 3,2x120Ahs, 24volt system: The BMS I could lay my hands on is PWOD LiFe Po4 8S 24v BMS. Im kind of lost as I donot know if I can get purformance data from this BMS. Is it worth anything or I should just forget and get a different BMS brand?
Based on my own experience with solar power systems, and lithium and AGM. putting batteries in series are great for efficiency but terrible for the battery life. internal resistance grows immensely during charge and discharge.the only way I've got single cells to balance is to hock individual pannels with individual mppt charge controller(6s cells in series with charge controllers connected matching each batteries polarity) to each cell .that helps a lot with cell life.6x10a mppt charge controller @ 4.0V =60A charging current at peak @24v.each cell will be perfectly balanced.THIS INFO IS BASED ON MY OWN EXPERIENCE.
If your battery come out of balance, the easiest way is to do it the same the BMS in his previous car does it. When the first cell reaches the CV voltage, the BMS turned the pack CV down until the high cell is below the balance point. His previous car had a constant voltage of 328V, but will reduce it if a cell is to high. On this setup, when he saw the first cell hit max voltage, reduce the CV to the current battery voltage until the high cell is pulled down. Then increase the CV voltage and repeat until you are back to the normal voltage. This is one of the reasons you need a powerful solar system, so the battery is able to balance regularly. (The reason I know how the BMS in his previous car works, is because my car also have a 80 cell LEV-50 battery pack, and have had my seriously out of balance many times)
If every cell were perfectly matched, which of course they are not there is always some small deviation. And the real imbalance comes from the connections and wiring. For sure there are major differences there. So the path for each cell and each set of cells has a different resistance. That is where the imbalance comes from. Balance on discharge is as important as balance on charging.
Finally have sun today in SE Colorado after 5 days of clouds , but it’s still -4°F, good for the solar electric panels, but too cold to use the solar water heat collectors. Propane and firewood!
Good call. Just love those sunny/cold winter days. Not well known that the power produced by solar panels is higher when it's colder due to higher voltage but the current is determined only by the intensity of the light (photons) from the sun (insolation). So for the same intensity of light in summer and winter, you will generate more power in winter.
Hi good morning, I think unless you top balance the battery to 3.6/3.65V the imbalance might happen again. I think the voltage from 3.55-3.65V is the necessary absorption, as you said it's 99% charged at 3.5V, the remaining seems to be required Absorption. And Setting 3.6/3.65 absorption and 3.4/3.5V float might be better for maintaining a balanced battery. Just my opinion. Thanks.
he top balanced before. he just needs to let the BMS balance his cells as they are charged and discharged. perhaps his BMS is not doing what he wants exactly but all cells with spread out from each other a bit as they are charging and discharging.
@@OffGridGarageAustralia Hmm, in my opinion 3.3V could be too low for an absorption voltage. I think the basic idea with absorption will be when the cell voltages increases with very less current input. That happens in the 3.6V range I think. And I also guess the SOC of each cells can't be determined accurately with the constant voltage unless it is in the 3.6V range.
Yeah, I hear you. But if you charge with CV to say 3.3V only, the absorption time would be very long and the voltage could not rise above that voltage. I once charged a cell to 3.25V only with CV and it stopped taking current after a long time. Rising the voltage just slightly got it charging again. So from that, I think absorption is happening at any point of time. More testing under way.
This is what I have been saying in my comments to you for a while. You need to take the charge up to 3.5v but balance from 3.4 each charge to keep pack in balance. These cheaper cells need a fair amount of balancing. My BMS high volt cut off is 3.6
JD: Wait…what? Are you trying to take credit for that which has been common knowledge for a decade or more and revisited in this video? BTW…your voltages are a bit off, your BMS knows better. Just let it do its job after you top balance when new (and occasionally thereafter if you so desire). Also stating the obvious concerning “cheap cell” balancing issues seems a bit presumptuous from where I sit. Just enjoy the videos and absorb the wisdom.
On your shut off settings for the BMS you set both time and voltage. If your BMS stops charging at EITHER time OR voltage on cloudy days it may be shutting off too early due to time expiring before reaching full saturation which could (theoretically) cause some of the batteries to have lower saturation and therefore become discharged earlier than others. In other words, on cloudy days it may require more than two hours after reaching full voltage to obtain full saturation.
You mean charge controller not BMS? The BMS does not charge the batteries. Well, that is partly true, but if you leave the absorption time for too long and the current is low (as with cloudy weather) you will end up charging your batteries to 95%+ every time. I don't want to do that though.
Mistake makes us to practice. Practice makes us to perfection. Perfection makes us fascinate. And we can't stop thinking so there are some mistakes again... lol
Thanks for the video. It all helps :-) You say that 0.2A balancing current makes "no difference" when they are charging at 18A. That's not quite right. It won't happen quickly, but over a period of days, some cells would be charging at (example) 18A while others charge at 17.8A and so the balance will slowly improve, all time charging is being balanced.
You may think so, but the practice shows, it is not balancing at all. The 0.2A difference are not enough for high capacity cells. Maybe if you have a 5Ah battery, this will work over weeks but with the large 100Ah or 280Ah, it does not work at all. For these cells, an active balancer is needed which is being turned on at the right time (or better voltage).
Great work! Appreciate it. Thank you for the opportunity to study together! Best wishes from Ukraine 🇺🇦
Thank you. Take care over there!
Thank you for teaching us as you learn these things yourself.
I have learned so much from your videos! There is so much to learn and you are so good at explaining the key points from your testing. Your channel is the best I have seen to truly make the complicated simple to grasp and you do it with great music and personality!!
Thanks a lot, David. Appreciate your feedback and kind words.
Hey! Tried this and it works! My batteries have a complex installation and I really didn't want to take them out of place for servicing. I achieved balanced cells merely by lowering the overvoltage cutoff to 3.45v as you suggested and voila! Thanks!
No matter how many times I watch your videos I always seem to go back and learn something new YOUR videos never get old my friend
THANKS ALOT 👍🏼🇺🇸❕❕❕
Wow, thanks
Your explanation of absorption was great, it really helped to visualize that part of the charging process! Where people can visually see there's still so much energy that can be packed into the battery even when you've reached the right voltage.
I've explained absorption before to people that it's like filling a cereal box. You can quickly fill it up to the brim but still not reach the gross weight of a full box until you kind of shake the box and let it settle some. Then you can pour in more. It isn't until you reach the right weight that you can consider the box "full" or "saturated". (The height would be the voltage, while the weight would be the current.) So the "absorption" phase is kind of like shaking the box while you pour in more cereal.
No need to put up the footage from the past 3 days if you feel this video sufficiently explains/educates people on what you learned. It's a wash of whether that could be helpful - on the one hand, people will see the entire process of how you were troubleshooting and learn along with you, but on the other hand it could actually complicate and confuse the message of what ultimately needs to be learned. With the deluge of information people face these days, I tend to think keeping things simple is better, that the value of watching you troubleshoot is negligible since you explained your thinking process pretty well here. So if you're comfortable that there's little to be gained from your footage from the past 3 days, I'd say "spare yourself the effort (and potential embarrassment 😆).
Your cereal box analogy is pretty good but it tends to apply more to flooded lead acid. In the case of lifepo4 that extra energy you're pushing in to the battery is done by fixing the voltage so that the battery cells that are already fully charged cannot accept any more because they resist this voltage but the battery cells that have not caught up yet can accept this voltage. In bulk you were charging based on fixed current but now you're charging fixed voltage. This means that the individual cells that are lower in charge are now going to be able to catch up to the ones that are already charged fully.
Why don't the more fully charged cells also continue to take a charge and end up over charging during this absorbtion stage you may ask? Because you are now keeping voltage fixed and any cell that's fully charged will resist and push back against this voltage. The only way to make them charge more fully would be to increase the voltage.
Why didn't the lower cells take more charge during bulk you ask? Because there are always slight variations between battery cells resistances.
So why can the lower charged cells accept a charge now when they didn't before? The answer is they did, but they just did so at a slower pace.. now you are giving them time to absorb this continous constant voltage over time and bring them up to the same threshold as the other cells at which point they will also start to push back against the voltage.
Think of it like teaching a class of students that vary in intelligence. The bright kids catch on quick and then sit there already educated but learning nothing new whilst you continuously repeat the same information over time untill the slow kids catch up. This repetition of information is analogous to the repetition of applied voltage over time or absorb stage as we call it.
Well i have learned a lot from him, especialy his mistakes.
@@juskarn Thank you!
@@juskarn i was going to comment that the cereal box was a good analogy, but your teaching fast and slow kids in the one class really is perfect!
Huh, 3 years later bought my first LiFePo 4 Cells. I was so busy to put the box together, and forget balancing 16 cells in parallel. I measured the resistance of each cell and there were no big difference. On the end, the BMS had problems with one cell, which always hit the top voltage at first. So I decided to disassemble the whole pack and start from scratch. I didn't even have a charger for 3.6 Volt, but remembered, I have the same buck converter as you show. It is now two days charging up to 3.6 Volt.
Now seen your video, o ha, ooh, damn, good, fucking great, now I understand about charging voltage, absorption, and how to handle my 320AH battery pack. Thanks a million. 👌😎
I appreciate your efforts. we are all learning together.
Thank you!
Indeed we are all learning this solar together. But so rewarding ❕❕❕
Thanks Andy 👍🏼👍🏼🌞🌞🌞🌞🌞
Hi Andy. I will give you my opinion. I made a battery with 22 LiFePo4 cells and installed without BMS on a scooter. 2 years after almost daily use I don't see any imbalance. After much reading and watching videos of experts, I opted for the technique of bottom balancing instead of top balancing. The explanation is simple. All cells have a common minimum, but not all can have the same maximum.
I unloaded cell by cell until its minimum tension and left it to rest for 2 days (the tension will naturally rise a little, being necessary to repeat). With all the cells equal at the minimum voltage, I connected them in series and connected the charger until it reached 80% of the maximum capacity. It is my safety margin and I guarantee that all cells are able to balance themselves at this voltage. LiFePo4 chemistry is very stable. It's just my opinion. Good job Andy.
Thanks for sharing. Interesting approach indeed...This method will work as you only charge to 80% capacity, that's correct. How far down do you discharge the cells during operation?
You rotten sod rubbing it in about your lovely weather and how we are freezing and your going in the pool to cool down !
Great episode as always. Lovely to see your frog at the end.... kept thinking of them when I saw your green battery indicator on your phone. Learnt a lot from your channel. Thanks
Thank you 🤗
You can keep your 31 degree weather. I'm going ice fishing. :)
Dear Andy, love your humor and most practical demo of solar system building.
Just went back to watch your first episode from very beginning. Love it and enjoy it.👍
Wow, thank you!
You been my teacher and I've learned a lot from you.. I'm using sealed wet cell and I know If I took my batteries and disconnect from my system, the solar power of 1000 watts would just take over and maintain my 12 volt / 1000 watts requirement. I really think you very close on solving this.. I live in sunny southern California and my generation has been excellent. If you can master using your batteries banks with the solar system and normal load usages at the same time, then I will upgrade to lithium lifepo4. Thank you for teaching us !!
I had similar issues, and what worked for me was this: Charge the pack until one cell peaks. I used an 8S charger and did 8 at a time so I could see which cells were topped out at 3.65V, and which were lower. Then individually charge any cell that wasn't topped out. Then charge the pack again as an 8S pack to see which cells were still not peaking, then I charged those independently again, and after 3 rounds of that, all were very well top balanced. You can charge the individual cells with a charger while still in the pack by just using alligator clips for the individual cell. I use a battery charger for the independent cell charging because it measures the AH added, and it shuts down by itself so I don't have to watch it.
Balancers are only for maintenance, you are definitely right on that. You must balance the cells before you can even think about using a balancer, BMS balancers only work when batteries are very close to each other for state of charge. When I had one cell peaking in the 8S banks, the other batteries were anywhere from 6 amp ours, to 84 amp hours lower! I came to the conclusion that adding to the low cells was way more efficient than discharging the high cells, as that is how I started but quickly realized it was a flawed approach.
Wery interesting! Can you explain, what does it mean? I have all the time same three cells, that are higher then others for around 0.010- 0.035 mv when charging, especially higer then 3,5v and in some time after stop charging their voltege goes lower on 0.020- 0.040mv then othe cells. And balencer begins to charge them. I did paralel topbalance befor assemble. I use Daly bms and Neey 4A smart active balancer. I see that during the end of charging, that 3 cells runs up, balencer discharge them, deviation voltage goes from 0.050mv to 0,004mv, charge stops, and after that, when bettery goes in rest, voltege goes down, and that 3 cells become lower than others... They goes much lower ( near 0.080mv) under load 60-90A. Without load, they also steel lower. I set balancer to continue balance after charging to rest to until 3,330v and usually get 0.010 mv diff. But in this case next charging shows bigger then 0.040 mv different, becose other cells gets some deviation between one another. Maybe that is normal behavior? Maybe, I have to charge battary to 3.65v per cell, and then charge that 3 cells individualy with 3,65 v automatic Lifepo4 charger?
Just watched this video. Experiencing the same problem on my golf cart project. I have a 135A 14s LiNMC battery with a JK BMS, a 300W solar panel roof, a Victron 100 20 MPPT, and a Victron 712.
Massive amounts of sunshine here in So. California. Trying to keep the solar power system from triggering the BMS. This video has gone along way to help me understand the MPPT settings. Thanks...
Great insights there. Thanks for sharing with us! You learn when you jump in the deep end - if you were mucking around with cheaper, lower capacity or fewer cells, you wouldn't worry about these subtleties as much.
So true! It all looks easy when you watch other videos but building a battery yourself is more challenging than expected. Ot at least, it can be...
Just wanted to say thank you for showing us the whole process as you learn about charging. I am building a 12v LifePo4 battery right now and am in the same situation and find it all confusing about what settings to use, but watching these video's has helped a lot!
LifePO4 really prefers to take all you can give it. the float charge is for lead-acid batteries. and the absorb is also for lead-acid batties. it wants the bulk charge. that why they disable or have to reprogram the mppt chargers as they are not designed for LiFePO4. study up and you will find the correct information.
Thank you Shawn, much appreciated!
Always a good day when I see a video from @Off-Grid Garage :)
Glad you enjoy it! Hahaha, thank you :D
I think this was one of the best episodes for learning and conecting things in my brain !
when i test lead acid batterys i have this system, i charge and leave on float for 3 days to let all the energy absorb, i stop the charge then i test the voltage after an hour and then after 24 hours another voltage test and a 50A load test and then i choose the batterys closest to each other to put in a battery bank for solar, it's just the way i do things after years of charging used batterys and resurecting them for solar powerbank use but after watching this vid it clicked, somone else has similar thoughts ! differant chemistry i know but cool to see a similar thought process in somone elses head !I really really enjoyed that one, i love learning alongside you ! keep it up :)
Thanks for the feedback. I've got this effect all the time and step by step things make starting sense... Then I need to test and confirm that new learned, so it all takes time...
I only found your channel recently. I love the correction you made to your graph at 8:25. LiFePO4 batteries charge with a phase-change reaction, so their voltage is fairly stable through much of the charge/discharge cycle. You can DIY a quick and easy charger by combining a CC circuit with a CV circuit, which is essentially what you did. For a small cell (AA sized) application, I used a LM317 linear voltage regulator paired in series with a mosfet as a linear current regulator. Worked like a charm.
hi ANDY there are many teachers in this world, but very view can explain a process that everybody can understand it. u are one of the view exceptions to make ur presentation clear. it was the first time i see the total picture of charging a lifepo4 battery. thank u great job. i am the German guy in Texas and just started up my 30 kw system with a 8 kw solar system. i am using a SOL ARK grid tie inverter that can start a back up generator in case the grid goes down. i will make a you-tube movie the next few month and will send the link to you.
again thanks for all the patience and smarts you have. viel glück Jan
Excellent detective work there...
It's even harder to build an understanding when you have experience that needs to be forgotten because it no longer applies.
It would be interesting to see what the settled voltages of each cell were, after you carefully saturated each one.
Perhaps they each have a different saturation voltage... This would explain why the voltage based balancers can cause trouble!
This is helping me with my battery so much. Thank you youtube algorithm for leading me to these videos because I have the same bms. I have been having lots of trouble balancing. Before I was trying to balance during charging. I will take the battery to 4.1V/cell average (LMC not LiFePO4) and then balance after because the 200ma balance is so low even for my 68ah battery. Thank you!
Subscribed!
Thank you very much. I'll do another big video about balancing soon. That'll be interesting too. And controversial ;)
Andy please don't annoy me with the wonderful weather.
I have been digging out my panels from inches deep for the last week to be able to charge my batteries.
This video is the most informative you had made so far.
I will pass you from amateur to pro battery builder with a B+
You still need the 10A battery equalizer to help with the lifepo4 algorithm.
Put some voltage on these panels so the snow melts!
I'm probably only a C+ at the moment but came a long way...
NOOOO, no balancer or equalizer. They will just hide the problem. Once I found the issue, maybe, but for now, I need to dig deeper....
@@OffGridGarageAustralia I need more info about the voltage I need to put in the panels. When is freezing rain I have to spend hours scraping the panels.
@@OffGridGarageAustralia I installed version 3.1.1026 but it doesn't work with Samsung DeX. Regular phone is fine.
Great Video. I've been experimenting with a Growatt 3000K 24v 8S 3.2 cells. And It is very confusing to get all the parameters rights. Your video has clear many questions regarding CC/CV, voltages and amps. I am still playing around but I think I have found a sweet spot for my setup. Thank you very much for sharing.
Best video so far. Thumbs up.
And thanks for sharing the new app release.
Thanks John, much appreciate it.
Your frustrations make life easy for the rest of us. 🤣. Thanks for your videos. Very informative. In Southern California its sunny always.....until I start experimenting with my solar. ⛅☀️
Thanks Kevin, happy to share everything I find.
I know what you mean, there are always clouds in exactly my area when I want to test something. Blue sky all around but this one cloud ⛅
Exactly, its the same when you need to really equalise a big battery like an electric motorcycle, you charge with a low current to let the BMS do his job, thanks for the clear explanation 👍
Very insightful, excellent material to ponder. You have hit on an issue that I have been thinking about too. The longevity of the the batteries is greatly diminished by charging to 100%. a combination of voltage and current monitoring must be the answer. The tolerances are so tight as you point out it's so difficult to get it just right. Keep up the good work. Perhaps keep a log of the batteries that are always the highest and lowest to see if their performance deteriorates faster than the others. Keep testing to find the sweet spot! Thanks for your video
Hey, Andy! Great video! The problems that are the most difficult are also the ones that will teach you the most. You already made great progress and learned a lot. I have no doubt you will find the settings for the charge controller and bms that work for what you want. Good luck my friend.
Thank you.
Someone that shares his thoughts and is worth listening too!
Best videos on solar setup hands down!
This makes a lot of sense versus the common 'just top balance' advice that is usually given
Why not set float voltage to be the same as the absorption voltage? This will allow the BMS to continuously balance cells as well as allow solar to supply any loads without having to cycle back to bulk and absorption mode again
Yes,, that is how it have to be for grid connected batteries.
Hello. yes, the same here.
Yes, set Absorption = Float. It will be in the next video!
@@OffGridGarageAustralia yeaHHHH waiting for this Video from Spain and ready to get all hardware to copy your experience! we have a lot of sunny days as well in this country.
No, never do this (see my detailed answer elsewhere). Batteries are not capacitors, even if the amps are reading zero there are going to be eddy currents at the potential wall and overcharging above it if the charge controller is left in that state. Setting the float high enough to actually get the BMS to top-balance the cells is also high enough to overcharge the battery or greatly reduce its cycle life.
You want the charge controller to charge the battery high enough for the BMS to be able to top-balance it (e.g. bulk/absorp target minimum 3.45V/cell. 3.5V/cell is better with the absorption time set to 0), and then for both the charge controller and the BMS to both stop messing with the battery until the next charge cycle (e.g. float setting should be no higher than 3.35V or so).
-Matt
you're the best ! I literally want to go to Australia specifically to hangout with you 😊. I enjoy learning with you and appreciate your fun attitude to figuring out problems 👍
By the way I am in the middle of this exact issue you encountered here . Just did a single cell to 3.5v taper to < 0.1amp for each cell..I then paralled em and did the same thing.
Waiting for some load testing equipment to re-test. Fingers crossed
Thanks so much!! I have learned more from this and your next video than I have learned from tens of hours of solar/charger/battery videos over the last year or so
Good absorption explanation.
Finally pleae at what voltage to set for 1. Absorp vol 2. Constant vol 3. Float vol. Thanks in advanced.
Fantastic Video. I got lost in exactly the same trouble 1,5 Years later with my cells and that video was THE EYE-OPENER. Where the hell did you get these module FOR FREE in 2021???
You work so hard !
thank you for doing all this, saving me much brain pain. keep the froggies coming
Will do! Thank you Dirk!
I'm building a 18s LiFePO4 bank for '48v' Pb replacement. Thanks for the great info!
You're getting so good at these videos!
It's very accurate what you mentioned about every system being individual too. It's the reason I get frustrated at "kits" being sold online with the expectation that you connect A-B C-D etc,and it works, when it's much more detailed than that, at least to get good solid performance, that lasts like it should.
I reviewed a battery kit from a local supplier last week, and found that it was quite easy to balance the cells by leaving the (Lab Power Supply) charger connected overnight with the current limited to a bit under 100mA. The balancer took care of soaking up the excess power to the high cells. The same goes with my Daly, however I have balancing enabled throughout the entire charge procesas, all the way from 3.0v. It's a Hare and Tortoise type scenario, slow and steady is nearly always best.
You cannot build such a battery from a kit without understanding and testing it afterwards.
If you have low capacity cells this method may work but with these 280Ah cells, there is no way the BMS will balance them unless the charger is off and they are already on a high SoC and in the steep part of the curve.
To me it makes since to charge into the upper voltage peak to get out of the flare zone to know all your batteries have absorbed the bulk of there capacity. It also seems that it’s much easier to balance in that upper voltage peak since it drops quickly to the flat region so quickly. Maybe if you raise charge voltage per cell to 3.45 or 3.5 that will allow the batteries lagging behind time to catch-up in bulk mode and give the BMS a little more room to work. The trick as you have shown, at least on the first go, is that it’s a little tricky to get them balanced at first but maybe this will allow them to stay more balanced. I am learning with you and am waiting for my batteries to arrive, so thank you for all your hard work and then sharing it!! I am also considering using solid copper bars between the batteries, 5mm X 19mm X necessary length.
Thanks for your feedback and kind words.
I was thinking the same at the beginning and hence I chose to charge to 3.4V as this is already in the steeper area of the curve. But yeah, you're right the higher you go the steeper it gets. The problem is that if you have a lot of solar coming in at this point of time it quickly gets out of control as these cells charge very quickly and go over 3.6V in no time. The charge Controller keeps charging as it only sees the overall voltage but not individual cells. I had this twice now and decided to lower the voltage for that reason. There is still a lot to consider and no right or wrong... just a different :) And that's what I'm doing right now, trying different settings and see what consequences they have.
Thank you for the additional information, this is great stuff! I am looking forward to more videos! Keep up the great work!
The BMS will handle any over-charge conditions on individual cells, regardless of what the charge controller is trying to do. But even without a BMS, LiFePO4 cells can tolerate up to 4.2V before the electrolyte starts getting damaged. Nobody ever charges cells above 3.65V so there is actually quite a bit of wiggle room there. You still want a BMS, though, to ensure that no cell is over-volted into damaging territory.
If you are finding individual cells going that far out of balance while all the other cells are perfectly fine, then you have mismatched cells and you need to replace the ones that are going out of balance with new cells. Yes, this does mean that now your new cells will not pop-up as much as the older cells (due to less capacity in the older cells), but that's fine if the older cells represent most of your battery bank. It won't hurt anything and it means you can keep using the battery pack without having to wholesale replace it. Its an economic decision... do you replace the whole thing, or do you replace one or two cells? If the number of cells you'd have to replace gets too high, then you replace the whole thing.
You still absolutely need a BMS for the short protection, low voltage protection, high voltage protection, and to prevent a meltdown if an individual cell goes too far out of spec.
-Matt
Thanks that was a big help. Just starting with my first lifepo. Was scratching my head on what to set my charging parameters
Thanks Mike. There are heaps more videos on how to charge LiFePO4 correctly here on the channel.
You are doing great things.
Thanks for being you.
🐸
Thanks so much 🐸
One thing that may be happening with your cells since some are newer than others is the potential for some variation between manufacturing batches. Another thing I have noticed with my smaller cylindrical LiFePO4 cells that are all new and from the same batch is that they seem to have a wake-up period of a few cycles after being stored for a while (1-3 months) where they don't pull full capacity and then after being cycled a few times they come back. Not sure why that happens but it seems to be a thing. I wonder if since those batteries have such a large internal surface area, it just takes a long time for them to fully saturate.
I have an active balancer on my pack that will balance at 2 amps so I set the float to happen around 2 amps so that the batteries are allowed to balance. I have the balance voltage of the BMS set to 10mv below the setting of the active balancer. When they were out of balance at the beginning I would see balancing happening on the active balancer during bulk and float but now they are usually all fairly well balanced during the absorption stage so the active balancer only comes on when the BMS isn't able to balance which is now fairly rare.
Very true, think of it as if you were filling a drum with foam peanuts. Once full, you tap it a few times more electron settle themselves, and you add more til your full. A good balancer will do this an as you say it takes a few cycles to reach steady state.
Interesting comments. Thanks!
I ask the same question why cant you just make the absorb and float the same voltage? I suspect it may have something to do with What Comment is stated on Emily and Clark's channel, but I dont fully yet understand it.
"""I’m glad you mentioned low current overcharge of LiFePO4. So many people seem to believe that only the charge termination voltage matters, and neglect to notice that the cell manufacturers always stipulate a 0.05C charge termination rate. Charge to that voltage at a lower current and you’re overcharging.""""
Reply from Clark
"""Yes, and that can happen so easily with solar or while using your electrical system during charge.
Honestly I didn't understand this as a problem when I started this project. Solving the low current overcharge is what made this interesting to me."""
Yeah yeah rub it in rub it in! :) You have nice weather and we have snow and cold. Really felt that intro :P
Glad you liked it!! 😁
I did. Btw Andy could you perhaps consider getting a po box that we can send stuff to. I was thinking sending some diffrent dc fuses you could test/dissassemble or just send some random stuff.
Anyways really enjoy your channel and your personality. Best regards from northern Sweden.
The full charge voltage is a steep curve, even very slight cell variations will show quite big voltage differences. The remaining capacity of the cells at this point is very small , therefore dont worry about it. When the battery is in a low state of charge, the difference becomes more important as this is more related to differences in cell capacity. I use cells in series parallel to allow cells to be mixed and matched to equalise capacity. Its very easy to over think this, Lifepos really arent all that fussy in real life.
At the end Sparky the Frog, yes!!! Hm, I am little bit confused, I was expecting that 3.55V is already on the steep part of the voltage curve, but maybe because of the huge capacity of your batteries this is also relative. The problem ist that you can not measure the current at a cell level(but I think this is obviouse by now). The question is how to overcome the slightly difference in the charging/discharging behaviour of the cells. I'm afraid that the only way will be, even if you don't want to hear it, sorry for that, the usage of an additional active balancer or to determine the cells with simmilar behaviour and put them together with their own BMSs. Any other ideas?
As nelo says, active balancers can do max 10amps, but if you put 10 balancers in parallel they could do 100amps.
I think the solution is in not charging to high and let the cells absorb for longer. So I'll do some testing with 3.35V max charge (~95%) and let them absorb until the current is low. I'm freaking out if cell voltages go higher...
@@OffGridGarageAustralia Settle petal, just assume the position & say hummmmm. Get 16 hi/lo volt audible alarms, 1 on each cell & charge/discharge each cell manually with all the spare time you have. I have just ordered an active balancer so I don't have to freak out when my pack is finished. Cheers Scotty
Yes mate you are on your way to be the best BMS, absorption needs time.
for me i do not go for the amps but for the volts for 500 volt that is meaning
10 units from 50 A x 50 V that is a total from 160 cells in serie here a BMS is not working.
they are there but then you have to go for a EV BMS.
Wow! This was a year ago. How much change from this to today! This was a big one and glad it came up, one does kind of get stuck thinking most about volts and with lifepo4, current is in ways 1st. This vid would be a good one to do again.
Yes, some of the older videos needs to be re-visited and 'upgraded'. But we have covered these topics in other videos already.
I just ordered two of the JK BMS. Where are these chargers? I have 4 cells peaking at 3.6v while others are as low as 3.1v :( and the heltec balancers aren't working enough. Probably from such a large differential vs only 5 amps of redistribution. Thanks for all you do!
what an amazing series learning lots just like you did
Hi Andy. I could be wrong, but after watching your video up to 3:15, it seems obvious to me that you have at least 3 different connections (2 different busbars and one flexible conductor) connecting the terminals of your cells. I really believe that these variations in conductors between different cells causes that a certain cell charges faster than others and also discharges faster than others. Reason why?
I noticed this phenomenon in my own battery, where I had the first four and last four cells connected with standard iron, but between cells 4 and 5 I had a different wire (as you have between cells 7 and 8). Then I wondered what is wrong with cell 5 as it always charges faster and also discharges faster. When I then made the change so that there is a standard iron between all the cells, the problem disappeared. In my view, even a small variation in the resistance of the conductor between the poles makes it impossible to achieve balance.
I have a very simple 4 bar led voltage meter on every parallel cell group. This gives me a rough indication of soc. The way the individual meters behave in relation to each other also gives me a rough idea of state of balance. When the cell voltage is at a point of turning off one of the led bars, at that time I can see how long it takes others to follow suit. The longer the difference between meter states, in relation to each other, the bigger the imbalance. They all light/turn off in unison when well balanced.
4 LEDs to show a very flat voltage curve of LFP?
For top balancing, I get mine up to 3.7V individually with a RC Charger and then I activate diybms and get them down to 3.55V to have them perfectly top balanced. I made all the experience you've made and it took weeks... :-(. And I fully agree, it doesn't make sense to run cells over 3.35V. There is next to no more capacity and it shows imbalance drastically... even with 800mA balancing current of diybms on my 48V 240Ah you can't manage it.
But no active balancer necessary!
Having -5°C here in Vienna, my PV made 24 kWh today :-)
Thanks for the info. Weeks, eh.....? OK, I just had my first week of head-scratching experience. Even I worked with batteries and charge controllers before, it's so different. I probably let the cells absorb at 3.35 and call it. Everything above makes me nervous.
Gruesse nach Wien!
Hi Andy! I am a novice at all this. But from my research on the internet this is what I have come up with. It is good to do an initial top balance at a very high voltage such as 3.65 per cell. A charge to this voltage will bring the cell to about 95% of its capacity. Even though you don't want your daily usage to go more than 80% as you have said. This is the way to get them balanced in the beginning. Some commenters have said that wants you achieve this initial balance they should stay in pretty close balance afterwards.
Because of the flat voltage curve you will never be able to get them balanced if you're only going to 3.5 volts.
What do you think? Maybe you could give it a try. Thanks for your videos. I appreciate all your hard work.
CC part of CC + CV charging process makes the charging process faster. Your batteries get charged in a considerably shorter duration. If you have enough time, no need to CC part. Best wishes from Türkiye.
Fabulous info and very clear, and thank you for all the effort you put into this, im learning so much from your channel 💯
Those little DC to DC buck chargers are ideal to charging your batteries and with individual power supplies, they will do your balancing too, after they have been set-up.
It is a good thing that 2 amp active balancing is built into BMS's now which solves these problems.. Battery construction has also improved..
Hi.
One thing that needs to be said and understood. When your battery reaches your target voltage, absorbe begins. The current starts to taper off and will eventually reach minimum current flow. Unless you turn off your charge controller, your voltage will stay constant. Your bms should be equilizing the cells. I am wondering if you bms is a loaded bms or a boost one. (Maybe its both). I suggest that you put your system to work with a load on your inverter. Lights, refrigerator, furnace, or something capable of lowering your battery voltage so your bms can equalize the voltage of the cells. Your BMS works all the time not just when the batteries are fully charged. That way when you get to the top end of your absorb that the voltage of the cells are equally balanced. One thing to consider is did you get the right BMS for your system. You will only know this if the voltage equalizes out properly under normal use.
I do not absorb. I have the absorption voltage to 3.5V and stop charging altogether without any absorption time. Voltage will go back to 3.35V as per float setting in my SCC.
I understand only wanting to go to 3.4v, I would like to charge to that point only too, but you will not get measurable differences in cell in-balance until after 3.4v.
Would it be worthwhile to top balance ~3.65v for maintenance, then dial it back and cap your “daily”charge cycles ~3.5v, to stay in the healthier SOC zone for normal operation? 🤓🤔🤷♂️
@@serversurfer6169 probably although the difference between 3.5 and 3.65 in % is less than 1%.
I never let my LiFePO4 go over 3.35v each. they still take plenty of current while sitting at 3.28v or higher, and sit there soaking it in for quite a while. It takes several hours for the whole bank to drop down to about 10 watts or so, and they've taken more than 90% of their capacity at that point. I don't have a BMS on them, but they stay within 2mv of each other all the way down to about 2.9 volts, and they come back up evenly. 18S32P heavily used ANR26650M1A that "floats" at 60 volts or runs down to 48 volts.
YES, great to hear my theoretical theory may seem to work well. I still haven't tested it myself but thinking about it all the time to do exactly that.
Thanks for your feedback!
@@OffGridGarageAustralia Works great, if you have many hours of sun for a very long Absorb Cycle. Who has that?
Did you top balance all the cell in parallel before you series them?
Yes he did, you should catch up on his other vids, all the progress is documented
You don't really have to do that. If they're reasonably close in voltage, you can assemble the pack and then balance charge it at a moderate current, say, .1 or .2C. The charger's balance circuit will set the cells to the same voltage.
Hi,
I also using the Same cells eve 280ah
The total battery pack is 48v 560ah
Total Solar Power 8 kwp connected to MPPT controllers,
My Setting in the Mppt are
Bulk : 54.6v
Abs time 1h
Float : 54.00v
Max charging current 140amps
This settings Works Fine for me for More than 1 year.
And in that time i Never Balanced the Cells again,
I think there is also no Need to Balance the Cells every time you charge. To 3.4v
Thanks for sharing your number of your SCC. I'll go deeper into this in the next video.
Your float is too high. 53.6V is the highest you should float, otherwise the voltage gets too close to the potential wall of the cells and can cause them to go out of balance as well as cause unnecessary wear.
There is no need to fear a high charge target voltage. If you charge to 58.4V the battery banks will still only charge up to around 90%, and still allow the BMS to top-balance the cells (which won't hurt a thing). Charging it over 90% typically requires holding the high charge target voltage for a period of time (i.e. setting a non-zero Absorption time).
If you only charge to 54.6V, that is right smack in the middle of the potential wall of the cells. The problem with doing that is that the charge controller will not be able to consistently charge the battery to any sort of percent-capacity. It could wind up charging the battery from a low state up to anywhere between 40% and 60% or so. It will be inconsistent at best. If you are seeing more capacity than that, it's because your float (at 54.0V is too high and essentially trickle-charging the pack continuously or causing extra bulk charge cycles to kick in and do the same thing... trickle-up the battery's charge state).
If you really want to conserve cycle life then you don't need to charge the battery all the way up to 58.4V, but you should at least charge it to 55.2V. That will give you a far more consistent charge state and will allow the cells to charge above the potential wall instead of inside the potential wall, resulting in a more even charge across the cells.
-Matt
@@junkerzn7312 thanks Matt. As I said in one of my last videos: if absorption voltage and float is to far apart from each other, the MPPT won't supply any power to a load once absorption voltage has been reached and the controller switches to float. It will wait until the voltage drops to float before starting a new cycle. The load will be supplied by then battery in this stage and not from solar as it waits for the battery voltage to drop to float again. I found this is a total waste of energy, the sun is out but the MPPT waits for the float voltage to be reached instead of supplying power to the load and leave the battery charged.
@@OffGridGarageAustralia You don't understand. The battery is STILL ALMOST FULLY CHARGED when it drops to a 3.35V Float. I will repeat that. The battery is still just about fully charged. You aren't saving anything by using a higher float value. Instead, you are reducing the cycle life of the battery.
The charge controller will still help supply power to the load and the battery will still remain close to fully charged at a float voltage of 3.35V.
I've said this four times now. You aren't understanding the difference between the LiFePO4 charge curve and the LiFePO4 discharge curve. They are different curves.
-Matt
@@junkerzn7312 are you getting angry now? What's wrong with you?
I had the same problem with my 12v lifep04 battery installed a 5a active balance board. That's sorted the problem took couple of days but it got the job done. The board was like £10 from AliExpress
Great stuff Andy!
Thanks, Dave!
Thank you sooooo much for a link to the app that actually works on my phone :)
Glad it helped, Michael!
This is one of the limitations when all the components in the charge path are from different suppliers. While they all kind of work they are doing this in isolation. The other issue I have with your system is that having loads connected to the inverter will mess with the charge profiles and balancing. As I said earlier I have a MPP-Pip5048GK and 3 modules of Pylontech lithium battery packs. Each pack is 78 amp hours at 48 volt nominal (16 cells) and each pack has its own BMS. Overall the battery BMS talks to the Pip 5048GK charge controller via RS485 and adjust the charge profile independently for each pack as well as the inverter output requirement. So battery charging is completely separated from inverter power output. So the charge settings I have cannot be change as they are set by the battery pack BMS and are as follows. Float voltage 53.2 volts. Bulk charge voltage 53.2 volts. Battery cutoff voltage is 47 volts. In my system the maximum charge current is 80amps. Hope this helps.
3.65v i think cut of charging voltage is right thing to do.....
Or capacity balancing ....add missing capacity with small cells...
Great Videos . I took my cc/CV boost converter and set it for the highest cell then charged the lower cells to match , I'm hopping this will work I think there staying on it long enough to get a saturation but then there's the last cell we matched to and don't no where it was in its charge cycle however this seams to work for me until something better comes along .
Ich glaub ich werde dein größter Fan!
BTW, lead acid needs the same absorption, but even more so. Usually if you take the LiFePO4 up to 3.6 and hold it, the current will slope off fairly quickly. Most of the energy is absorbed before about 3.5v and definitely by 3.6v/cell for LiFePO4, while with lead acid it needs to sit right about 2.4v/cell for considerable time. (measure voltage right at the battery terminals - otherwise current and size of connecting wire can distort your readings.) Your quick drop in current at 3.4v/cell is perfect. Float should be pretty close to that, maybe 3.35v/cell minimum.
Battleborn batteries has a lot of short videos, and some about the "absorption" needed.
Yeah, we could see this in the video when it switched to Absorption and the current went down from 18A quickly.
I'll have a look at their videos, thanks.
I built a 4s pack, and when I first got the cells, I found one which was low and charged it separately for a while. Big mistake. Because I had added several AH to it compared to the other cells, it was always high and the pack cut out before the others balanced.
Even with a 1A balancer board, it would start balancing... and then cut out, charger would shut off and I'd have to manually restart it.
What I ended up doing was taking a small 5A adjustable power supply, and setting it to 14.0/14.1V. Enough to keep the per-cell voltage above the 3.4V needed for balancing, but not high enough that the highest cell would hit 3.65V and cut out. Left it that way for 24 hours as (effectively) the balancer board kept balancing as the supply kept it topped up. Now, it's all nicely balanced, and I disconnected the balancer board and haven't needed it since.
This info really made sense thank you
Is there a reason you couldn't hook the battries up in parallel (assuming they are all nearly the same voltage) and let higher voltage batteries charge the lower voltage batteries? then when they are all the same hook them back up to your system in series?
Hey Andy! Love your vids but have a question:
What if i had a server power supply(whith the over/under voltage protection disabled) that outputs 14,2V@No Load, would it also taper the current when reaching 14,2V? My thoughts is that it will because the current tapers because of the battery inner resistance increases at the end of the charge cycle all according to Ohms law?
It will burn out as it won't control the current. Such power supplies don't have a current limiter and connecting a battery is like a short for it. It will try to deliver as much current as it can until something goes off in smoke.
I tried with a computer power supply and had this 😉🚬
@@OffGridGarageAustralia Ahaa, thanks for letting me know! Could I use it with a Victron solar charger or Dc-Dc Controller?
Hi Andy, great job from you as always. Can i kindly ask for your help. I use BMS JBD AP21S001 and facing problem with drying of my LiFePo4 battery during nigh when my inverter (Axpert King II) are in bypass mode. In application (blue small elefant logo from Xiaoxiang) i see 0,8A consumption every 2-3 seconds. Look like BMS is doing something and finally drying my battery a lot. Can you guide me what to check and how to adjust BMS option accordingly? Many thanks and have a nice day. B.R.
I think I read you note... Absorb 54.4... Float was what I would expect... so, shouldn't Absorb be about 57.6v or slightly more? What have you set your time after reaching Absorb before entering float? After listening to the entire post, I heard you say "two hours". I have never understood what Absorb time should be for LFP and have seen many folks use as little as 10 minutes.
Thanks
It's true, I only have it in my system for 12 minutes maximum, two hours is for a lead acid battery.
Hallo: Dank deiner Videos habe ich mich inspirieren lassen auch eine LiFePo4 Batterie zu bauen! 8 Zellen 280AH! Genau dieses Thema hat mich auch zum nachdenken gebracht! Ich werde probieren die Obergrenze der Spannung auf 3.65 im BMS zu stellen und den Laderegler die Erhaltungsladung und Normale Max Ladungsspannung auf 3.4 x 8 zu stellen! Dabei sollten sich die Zellen ausbalancieren können solange der Unterschied der Zellen nicht 0,25V überschreiten! Schöne Grüße aus Österreich!
In order to top balance you need to be charging at no more than 200ma. So that the balancing circuit can eliminate charging on the highest voltage cell(s) while allowing the rest to charge. With 280AH cells the balancing will take forever.
9-12 in of snow yesterday. Had to shovel for the first time this season. More Monday, but may warm up well above freezing enough to melt it down, at least enough to clear the roads.
I cannot imagine this any more, we have pure sunshine all year around.
Great video! I'm a believer too! Sometimes, I feel like a solar monkey... Thanks for sharing all your trials and tribulations. The experiences and the data - all very helpful. I downloaded the newest XiaoXiang app - Thanks! The Play store only has 1014. Battery balancing is indeed a daunting task. I'm still looking for the sweet-spot where it can all run unmanned. I only have 8 cells in a 2P, 4S, 12V configuration.
Thanks for sharing, Peter. I will probably only charge to 3.35V eventually to stay save and don't charge the cells too high. The balancing and testing takes a long time but that's where I learn the most.
Jeez, you'd think someone named Peter would know it's spelled Monkee. 😜
Just don't over-Tork your bolts!
Sorry if I'm confused. But did you come to a final result about how to get these batteries even and all charged up? Is there a summary what to do? I have pretty much the exact same setup as you as far as batteries go I just need to get the other stuff. Looks like BMS is first to be safe. Then Charge Controller and panels. Just finishing assembling a cc, cv, 12A 60V power supply, so geting ready to finally unbox and charge them. In Southern California I will get (a bunch of) PV and an MPPT SCC for PV charging. But I've heard initial charging can avoid many of the issues with them (dis)charging at different rates. I've heard a lot about voltage charging first and then amperage charging at the end. Also some info about letting them rest and then topping them off. So.. did you finally come up with a process for yours or does it change a lot depending on the Sun or what? Love your videos love your attitude thanks for the info.
Thanks Steve. You probably hear and read a lot about this stuff. So, the common sense in this is to top balance the cells before building the battery. All in parallel and slow charge to 3.6V, then let them sit until the current goes to almost 0.
I have learnt a lot about solar batteries from your videos. Im building a 8s , 3,2x120Ahs, 24volt system: The BMS I could lay my hands on is PWOD LiFe Po4 8S 24v BMS. Im kind of lost as I donot know if I can get purformance data from this BMS. Is it worth anything or I should just forget and get a different BMS brand?
I am really learning!!!!! ALOT! Thank You!
Based on my own experience with solar power systems, and lithium and AGM. putting batteries in series are great for efficiency but terrible for the battery life. internal resistance grows immensely during charge and discharge.the only way I've got single cells to balance is to hock individual pannels with individual mppt charge controller(6s cells in series with charge controllers connected matching each batteries polarity) to each cell .that helps a lot with cell life.6x10a mppt charge controller @ 4.0V =60A charging current at peak @24v.each cell will be perfectly balanced.THIS INFO IS BASED ON MY OWN EXPERIENCE.
If your battery come out of balance, the easiest way is to do it the same the BMS in his previous car does it.
When the first cell reaches the CV voltage, the BMS turned the pack CV down until the high cell is below the balance point.
His previous car had a constant voltage of 328V, but will reduce it if a cell is to high.
On this setup, when he saw the first cell hit max voltage, reduce the CV to the current battery voltage until the high cell is pulled down. Then increase the CV voltage and repeat until you are back to the normal voltage.
This is one of the reasons you need a powerful solar system, so the battery is able to balance regularly.
(The reason I know how the BMS in his previous car works, is because my car also have a 80 cell LEV-50 battery pack, and have had my seriously out of balance many times)
Good morning and good job
Thank you so much
If every cell were perfectly matched, which of course they are not there is always some small deviation. And the real imbalance comes from the connections and wiring. For sure there are major differences there. So the path for each cell and each set of cells has a different resistance. That is where the imbalance comes from. Balance on discharge is as important as balance on charging.
I'm snowed in but theres a lot of sunshine and its -15c so perfect solar weather
Surprisingly, yes. And the Sun is closer too.
Finally have sun today in SE Colorado after 5 days of clouds , but it’s still -4°F, good for the solar electric panels, but too cold to use the solar water heat collectors. Propane and firewood!
Good call. Just love those sunny/cold winter days.
Not well known that the power produced by solar panels is higher when it's colder due to higher voltage but the current is determined only by the intensity of the light (photons) from the sun (insolation). So for the same intensity of light in summer and winter, you will generate more power in winter.
Hi good morning, I think unless you top balance the battery to 3.6/3.65V the imbalance might happen again. I think the voltage from 3.55-3.65V is the necessary absorption, as you said it's 99% charged at 3.5V, the remaining seems to be required Absorption. And Setting 3.6/3.65 absorption and 3.4/3.5V float might be better for maintaining a balanced battery. Just my opinion. Thanks.
he top balanced before. he just needs to let the BMS balance his cells as they are charged and discharged. perhaps his BMS is not doing what he wants exactly but all cells with spread out from each other a bit as they are charging and discharging.
I can absorb at 3.3V, right? It just takes longer...
@@pilgrimvalle Yes, I know Andy did at battery build 2 video, but I am just suggesting coz the pack seems unbalanced now.
@@OffGridGarageAustralia Hmm, in my opinion 3.3V could be too low for an absorption voltage. I think the basic idea with absorption will be when the cell voltages increases with very less current input. That happens in the 3.6V range I think. And I also guess the SOC of each cells can't be determined accurately with the constant voltage unless it is in the 3.6V range.
Yeah, I hear you. But if you charge with CV to say 3.3V only, the absorption time would be very long and the voltage could not rise above that voltage.
I once charged a cell to 3.25V only with CV and it stopped taking current after a long time. Rising the voltage just slightly got it charging again. So from that, I think absorption is happening at any point of time. More testing under way.
Hello sir quick question What type of BMS and charger controller you using ?
Thank you very much for this crucial info :):):)
Won't active balancers help when used together with the BMS?
This is what I have been saying in my comments to you for a while. You need to take the charge up to 3.5v but balance from 3.4 each charge to keep pack in balance. These cheaper cells need a fair amount of balancing. My BMS high volt cut off is 3.6
JD: Wait…what? Are you trying to take credit for that which has been common knowledge for a decade or more and revisited in this video? BTW…your voltages are a bit off, your BMS knows better. Just let it do its job after you top balance when new (and occasionally thereafter if you so desire). Also stating the obvious concerning “cheap cell” balancing issues seems a bit presumptuous from where I sit. Just enjoy the videos and absorb the wisdom.
On your shut off settings for the BMS you set both time and voltage. If your BMS stops charging at EITHER time OR voltage on cloudy days it may be shutting off too early due to time expiring before reaching full saturation which could (theoretically) cause some of the batteries to have lower saturation and therefore become discharged earlier than others. In other words, on cloudy days it may require more than two hours after reaching full voltage to obtain full saturation.
You mean charge controller not BMS? The BMS does not charge the batteries.
Well, that is partly true, but if you leave the absorption time for too long and the current is low (as with cloudy weather) you will end up charging your batteries to 95%+ every time. I don't want to do that though.
Mistake makes us to practice.
Practice makes us to perfection.
Perfection makes us fascinate.
And we can't stop thinking so there are some mistakes again... lol
That's a good summary. Success and fail are close together...
Thanks for the video. It all helps :-)
You say that 0.2A balancing current makes "no difference" when they are charging at 18A. That's not quite right.
It won't happen quickly, but over a period of days, some cells would be charging at (example) 18A while others charge at 17.8A and so the balance will slowly improve, all time charging is being balanced.
You may think so, but the practice shows, it is not balancing at all. The 0.2A difference are not enough for high capacity cells.
Maybe if you have a 5Ah battery, this will work over weeks but with the large 100Ah or 280Ah, it does not work at all. For these cells, an active balancer is needed which is being turned on at the right time (or better voltage).