It's not just about AH remaining, it's about balancing the batteries. I'm now sitting at 61kw of LiFePo4. I was charging at 3.45v per cell. It worked well for a few months but I noticed when I get low on charge that my packs will get up to 300mv difference. I've increased charging to 3.50v per cell and the issue went away. You want to get into the steep part of the curve but not max out. I run two houses full time with these batteries. For those with pre-made packs it's 14.0v bulk 13.4v float, 28v bulk 26.8 float, or 56v bulk 53.6v float
Hello, just wondering which cells you have and the BMS?? Some have a setting to equalize when charging and when you turn that off it equalizes all the time and does a better job of keeping the variation low.. I bought 2 with active balance that does up to 2 amp transfers between cells..
You only want balance to start when the cells reach 3.45v/cell. For my 24v system I still use 28.0v bulk, 26.8v float, balance start at 3.45v/cell. I'm using eve cells sold by Gobelpower and 2a jk bms
I know you watch Andy at Off Grid Garage and he has done a deep dive on this subject. He initially set his charge voltage approximately where you were at (3.4--3.45 per cell). I believe he has since changed that to a slightly higher value due to the balance function of the BMS. Everything you have presented here agrees with what others have found out about this chemistry. LifePo4 is so interesting and makes one re-think everything we learned about batteries (lead acid) over many decades.
I too have watched most of Andy's vids on LifePo4. He did some extra vids after commenters mentioned balancing would be easier with slightly higher voltage. His tests I believe did not confirm this. I think he sticks with 3.45v per cell(13.8) and recommends an active balancer over the lower amperage passive balancer built into most BMS. It's a very interesting topic. I bought the same tester/discharger/charger. Pity it's only 5A charge at 13.8 odd volts. I now parallel charge a 10A and 20A charger and finish off with the EBC unit as its programmable to stop at a set current. Great unit to have for around $100.
Im using an EPEver 40 amp charge controller on my 200amp 12 volt Ampere Time battery. I had it set to Bulk 14.4V for 30 mins yesterday and Float 13.6V. Today I turned it down to 14.2Bulk 30 mins and 13.6V Float. Im going to turn it to 14.4V Bulk once a month so the BMS balances the cells once a month. Im on the fence about Floating at 13.5V or 13.6V. The only load is a mini fridge. Its plugged into a Xantrex Prosine 1000watt that Idles at 1.5watts in Power Save Mode and the compressor kicks it out of that mode 1/3rd of the time to run the compressor.
@@garyenwards1608 You don't want to float lithium batteries, it's not necessary, as we are not at risk of sulfation since Lithium is not a lead acid chemistry, and you risk shortening the life of the battery, as your still putting current into the battery. If you can't disable float stage in your charger, then set the voltage to something lower than the resting voltage of the LFP battery.
Thanks for this. The float voltage needs to be at a level where your solar panels will kick-in to provide power rather than the batteries. I use the "Equalize" setting on my charge controllers to occasionally ensure the BMS in the fully charged batteries will have the voltage to run its top balance program
I was just thinking of trying this on my CC. What type of CC are you using? Does it Equalize once a month? I dont see a schedule or time adjustment for the Equalize setting on my EPEver CC. Im using an EPEver 40 amp charge controller on my 200amp 12 volt Ampere Time battery. I had it set to Bulk 14.4V for 30 mins yesterday and Float 13.6V. Today I turned it down to 14.2Bulk for 30 mins and 13.6V Float. Im going to turn it to 14.4V Bulk once a month so the BMS balances the cells once a month. Im on the fence about Floating at 13.5V or 13.6V. The only load is a mini fridge. Its plugged into a Xantrex Prosine 1000watt that Idles at 1.5watts in Power Save Mode and the compressor kicks it out of that mode 1/3rd of the time to run the compressor.
@@garyenwards1608 You could set float to 13.4V and be below an active state of current flowing into the battery, assuming it is indeed fully charged before hand. Then, there's no risk of low current, over charging of an already full LFP battery.
@@s.mendez7160 What would you recommend for a boost voltage and duration? I've been thinking of elimination the duration and just setting a voltage of 14.4 but i have a few EP ever charge controllers all hooked to a single battery
Its only going to drop back down to that voltage anyway, so it makes no sense to charge the cells over 3.4v or the pack over 13.5v Anything else is little to no gain and detrimental to the battery. The only time you want to charge the battery to 14.6 < is if the cells are out of balance which is rare for a battery thats in good health. To keep it in good health is to not over charge it . Good video
....for me that's easy, I use the same battery, a TimeUSB 50 ah and a Renogy solar charger... just set the Renogy on LI default about once a month.. quickly goes to 14.4...but on user setting 13.8-14 for the rest of the month... I use mine for a solar powered a ham radio setup so absolute max AH available is not critical.
13.7 or 13.8 is a good charge voltage for a 4 cell LFP battery. You should have at least 3.4 to 3.45V/cell for balancing, not below. If you don't need to balance keep it at 13.6 ... 13.8V thats absolutely enough. On the other hand, you could also go up to 3.5V/cell without really harming the cell what so ever, but above begins the stress level.
Thanks for your test information.. I am building a monster dual 15kw 48v battery for 30kw at a top charge of 58vdc using 17 LiFePo4 EVE cells and have been watching quite a number of videos to basically learn the craft.. Still trying to settle on the top charge per cell between 3.4v and 3.5v with a bottom of 2.9 to 3vdc.. My 8kw inverter can accept an input between 40 and 64vdc so if I keep the voltage higher it will make more power for less heat because as the volts get lower the amps get higher and amp flow is heat.. Bought 2 JK BMS that are the slightly older version but have the 2 amp active balancer which allows the bypass of the stringing cells and charging them to 3.65v to get balanced cells.. Instead I will check all cells to make sure they are similar 3.0 to 3.2 near the bottom then assemble the pack, setup the BMS and controller and gradually walk the battery to 3.6v per cell to get 61.2v over a couple of days as the active balancer levels out the cells.. Once top balance is achieved I will back the voltage down to that undecided operational level.. As for the float voltage from the charge controllers I am thinking that I will set it just a couple tenths of a volt lower so during the day the solar panel production once the battery is full will handle as much of the loads as they can and to prevent micro charge cycles..
Note that the vendor specifications for a lot of these fly-by-night brands are just plain wrong. Often these vendors don't even know how the BMS in their own battery is programmed. For LiFePO4, if you don't have control over the BMS settings, you generally always want to charge to 14.2V (3.55V/cell). The reason is not to try to get the battery to 100%. That has nothing to do with it. The reason is that the BMS may not start balancing the cells internally at a lower target voltage and if the BMS's balancer is not operating, the individual cells will go out of balance and some of them will wind up at 3.65V (the BMS cut-off) despite you having that lower target voltage. Because of this, 14.2V is generally the best choice. 3.50V/cell (14.0V) is also a fairly safe bet. But lower than that is not a good idea. i.e. you can wind up putting more cycle wear on the battery with your lower target voltage than with a 14.2V target. So this is why you pretty much always want to charge to 14.2V. Don't worry about cycle life, charging to 14.2V won't hurt the battery. Discharging the battery all the way to BMS disconnect will put far more cycle wear on the battery than charging it to 14.2V will. Like an order of magnitude more. -- Now, for float, the float ALWAYS must be set to 3.35V/cell to 3.375V/cell. That is, 13.4V to 13.5V. NO EXCEPTIONS! This is the voltage range where load support can be provided without discharging the battery (for example, in a solar application), while at the same time not being so high that the battery continues to charge while sitting at that voltage. This is also the voltage range which puts the least amount of wear on the cells from sloshing around as the load changes and the charge controllers try to match it. If the float is set higher it will continue charging the battery, ultimately overcharging it. If the float is set lower, it will discharge the battery and also the sloshing from the load-following the charge controllers do will put more wear on the cells. -- If you are still worried about charging the battery up to 14.2V you can always take a little off the top after charging is completed by putting a load on the battery for a minute or two. If the battery is permanently connected to an inverter or a system that always has some load, even if only very small, you don't have to worry about it at all because the battery will more or less immediately drop to near the float due to that load, after charging has stopped. -- In terms of attempting to charge to a particular SOC below 100%... its a bad idea, because the BMS will generally not be able to balance its cells internally if you charge to a lower SOC. For discharging, if you can control when to turn off your loads it depends massively on the amount of load. For light loads (up to around 0.3C), a 12.0V floor gets you 95% of the battery. For heavy loads you can go lower. The issue with discharging is that discharging all the way to BMS cut-off, repeatedly does an ORDER OF MAGNITUDE more damage to the cells than anything else you could possibly do to the battery. Its ok to do it, it won't destroy the cells, but you are putting a lot more cycle wear on the cells by discharging them that low. Also, if you fail to charge the battery in a timely manner (like fir a week or two) after it has been discharged to that degree, you risk the cell self-discharge from taking the cell voltage into territory that will significantly damage the cells. LFP batteries are far, far more likely to be destroyed by over-discharging them / letting them sit while discharged, then by "overcharging" (holding them at a charging target voltage for days or weeks on end). Holding the battery at the float 24x7 is fine, but in that case choose the lower-end of the float spectrum. 3.35V (13.4V). And in solar applications you generally don't have to worry much at all due to the cyclic nature of the charging and discharging. -Matt
Notice that some vendors that claim1.0C as the charge rate in their instructions now recommend 0.2C on a regular basis and a max of 0.5C. They learned from claims and angry comments about early failure.
Hey Matt. I have a 100 amp lipo4 battery with BMS. My controller only has a float voltage to set (no bulk charge). I always have a fridge load running. What should I set my float charge? So confused. Thanks
@@dandunlap9111 I don't think I know of any controllers which only have a float setting but not a bulk (or absorb) setting. So the first thing to do is find and read the documentation on your controller very carefully. If you can't set both parameters then you'll want to get a controller where you can. That said, in a solar application where the battery is being cycled daily and charging drops off when the sun sets, you can temporarily just use the charge target for your float setting. LiFePO4 can tolerate being held at its charge target for long periods of time. But it isn't an ideal situation to be in and you will want to rectify the situation. -Matt
The LiFePo4 cells are far more durable when stressed at the top and bottom than the older Lithium Ion formulas so charging is less critical but as he showed you gain very little when pushing the limit..
Yes, the chemistry should give LIFEPO4 an edge if build quality is the same. But we have not had consumer grade LIFEPO4 cells on line long enough to draw a valid conclusion.
super useful thank you, this taught me so much about how my new lifepo4 battery works and what to aim for on my charge controllers and importantly why its the case. The graph was ideal way to understand it. subbed
Good Revision, I set mine to 27.6 volts.. I just got a new MPPT, Happy with Y&H 100A MPPT Solar Charge Controller 12V 24V 36V 48V Max 100V Lithium...30 bucks cheap but nice big screw fixing holes...3 x 375 working fine. I tried expensive Victron but 100/20 but kept blowing fuses even with 1 375 panel. So, I returned it. Think I am set for summer now.
I emailed eco- worthy on advise for programming victron mppt to work with one of their 12v 280ah lifepo4 batteries. They sent me a response but it dont make sense it goes against advise given in videos like this .. "We recommend adjusting the charging voltage and float voltage to 14.6V. This is a common setting for LiFePO4 batteries to ensure optimal charging and battery longevity".
This is because of what is a ‘common industry convention’ or concurrence as to existing charging device algorithms …’Implied compatibility’ in this way is mere marketing that sells batteries - Vendors are incentivized to tow the line…
You really got that one off... You missed the whole Bulk, Absorption and Float steps.. Bulk will shove alot of amps into the battery until it's at about 90%, then it will go into Absorption until it reaches the needed voltage for the bms and equilization (14.2 - 14.6), at that point it will drop to the Float voltage which is usually 13.6-14.0... Then the charge controller will maintain that voltage. Under charging your batteries like that is going to backfire on you eventually... But good luck..
i already lowered my stats but still i need to find the perfect timing cycle of all this because the lower i go the faster it goes and victron has the potential timing of this cycle... still testing my setup .. good thing is i never found my shed in error.... keep up
The problem with charging with low voltage is time you are losing the potential from the solar. at 3,4v it vill fill up but it vill need to absorb for hours pulling minimal current meaning the MPPT is just idling the solar panels
That's true, but we are also talking about the last 1 - 2% of the capacity. I would rather get more charge cycles than that last 2%. Hope that makes sense. Thanks for the comment!
@@OffGridBasement it is much more than just 1-2% as with lower charging voltige the power going in tapers off really early and you can lose 1h+ of solar
@@OffGridBasement with 3,4V you are reducing charging as early as 50-60% SOC depending of charging current using 3,5-3,55v is a better option as the dropp in charging power only happens around 90% SOC and is much smaler.
I enjoy your informative video a lot. I've been thinking of building a diy 12V portable power system just to learn possibly using a 1500W inverter and 2 or 300ah battery. My question is what amperage charger should I buy 30A, 40, 50A?
Lifepo4 batteries like to charge at 20% of the total ah capacity. 20A charger for 100ah battery... 40A charger for 200ah battery and so on. Anything that is slower is totally fine. Hope this helps! Thanks for the comment.
Any LiFePO4 battery can be fully charge to 100% if held at any voltage above the float range for a long enough period of time. Generally that means 3.40V/cell or higher. However, the amount of time you have to hold the battery there is variable. If you stop the moment it hits 3.40V/cell (13.6V), even after waiting for the current tails off, the battery is probably not fully charged. The main problem with using low voltages like 3.40V as a target is that the BMS probably won't balance the battery's cells internally at that voltage. So you wind up doing more damage to the battery rather than less as the cells go out of balance. For example, an out of balance battery held at 3.40V might have cell voltages of: 3.35V, 3.35V, 3.30V, 3.60V. An addition problem with using a low charge target is that at a high charge rate (e.g. 0.4C+) you will reach that target long, long before the battery gets anywhere near 100%. Like you'll hit it at 70% or even 60%. And with the current tail you might reach 80%. Also, once the cells have gone out of balance you can start to lose capacity at your lower target voltage because some of the cells will not reach anywhere near 100%. -- If you have full control over the BMS settings, you CAN charge to a lower voltage by ensuring that balancing starts at e.g. 3.40V and then using a 3.45V charge target. However, this only works well in warmer temperatures. In cold weather you definitely want a higher charge target, regardless. Most batteries that do not give you access to the BMS don't balance at that low a voltage and you need to charge to 3.50V/cell or 3.55V/cell (14.0V or 14.2V) to be certain you are engaging the battery's internal balancer. -Matt
@@OffGridBasement sweet I noticed also near by at my local college surplus they are selling 30 APC the 5kw version pure sine wave for 500 bucks, seems a bit high going to see if it comes down but I bet those little bad boys are amazing form the looks of it, I think they are low frequency too, I refuse to use a HF inverter, cant stand them
Hi sir I have Lifpo4 16s, It's connected by bms cable My battery wont charge until its 95% I believe its because the float charging volt is low I dont care about the 5% i dont need it But im worried about my battery longevity because it keeps charging between (soc 100% and soc95%) Multiple times through the day what do you suggest
The charge controller shouldn't go back into bulk charge after going in to float unless you are using more than your solar panels are producing. Does the charge controller have a re-bulk charge setting? If so, change that so it's lower than the float setting.
@@OffGridBasement No sir I dont have re-bulk I dont know what's really happening when i had a voltronic inverter my battery at day time was 100% al the time Then i switched to deye inverter now the battery charge to 100% then discharge to 95% then 100% .. 95% etc.. I don't know why this is happening because i have more than enough power from the solar panels If u have email or Whatsapp number i can send for you some photos
@@OffGridBasement I found this comment which suggests you can get away with a 13.8v constant float: ruclips.net/video/4SCgXrl-rqg/видео.html "I've mentioned this a few times before: I've got half a dozen UPS units using LiFePO4 cells that are charged 24/7 for 5+ years at a constant voltage of 3.45v per cell and they are fine. There's no way you could overcharge them at 3.35v per cell."
Lithium's don't need float voltage, that's for lead acid chemistry to prevent sulfation. @13.8V you risk shortening the life of the battery, as your still applying a small flow of current into the battery. Either change the float voltage to below the resting voltage of the battery, or figure out how to take the charger out of the circuit till its time to recharge the battery.
I partly agree. But once in a while you should slowly charge to 3.65V / Cell to give the balancer a chance to balance out all the slightly different cell voltages. That is only possible between 3.42V and 3.65V outside the flat charge curve area. Those cheapo batteries mainly have small passive balancers which need time. Only large 15kwh packs have active balancers.
Far too much emphasis on higher voltage & balancing, if the pack of cells are in series and identical they regulate themselves people get carried away with the whole balancing idea. Many people don't use a BMS and cycle 3.1V - 3.45V which is around 20 - 80% SOC and they work just fine. Balancing at higher voltage with a BMS is just stressing cells more than necessary and shortening their life. Better to concentrate on keeping the cells below 30 C for max cycle life. Compressing is also way overrated perfectly normal for cells to bulge a little when charging, space them out 5 - 10mm according to busbars and if they swell and touch put a piece of thin insulator between when discharged so they can't short out, cereal box cut to size works fine.
@@OffGridBasement You don't see the wires coming out of the top of your outside battery enclosure, it's probably the only visible wires in the video..They should come out of the bottom, run into under ground conduit and run into the house..
The only person I`ve found who HAS THE MPPT CONTROLLER I BOUGHT says..."There` s a way to set the voltage for lifep04 and all but gee I can` t remember what to do..." And he USES IT!!!! GOD DAMN! Now I have to buy another one and HOPE it comes with an ENGLISH INSTRUCTION MANUAL!!!!
@@OffGridBasement OAE 60 amp mppt 12, 24, 48 watts & 150 volts. The manual is badly translated. It has "lithium ion" setting and the manual says FLOAT is the only way to adjust the charge voltage. It` s running set for 12v battery, lithium ion type, 13.80 float voltage with two 190w HQST panels in parallel. Until I figure out whether it`s charging the battery I`m not connecting my larger, shorter cables or using series. I can`t afford test equipment. I`m running a 400w air conditioner....watt meter connected between the AC plug and inverter...and eventually I`ll be able to tell if the wattage on the mppt is going into the battery because I started with 3.3 kwh of the 300ah 3.8 kwh battery charge and reset the watt meter.
@@OffGridBasement 12, 24, 48 volts. I can`t think from total frustration. I can` t type or think right now. It has these numbers in product description. My brain is in knots from this garbage.
Is there a simple, affordable, easy to program charge controller? PLUG AND PLAY FOR A 12v LIFEP04???? The only settings in mine are battery type, battery voltage, and float voltage. In the manual it says the LITHIUM ION setting only has float voltage and it defaults to 13.80. The Chinese manual is INFURIATING!!! I`ve wasted so much money and time for over 2 years and I STILL DON`T HAVE SOLAR because I can`t afford the "Will Prowse" instructions!!!! Solar forums are like a technical JACKOFF SESSION of confusing nonsense and nobody uses 12v systems so poor people are SCREWED trying to get answers. I simply want to run a 400 WATT WINDOW AIR CONDITIONER and not destroy a 300ah Ampere Time battery using my solar panels!!!!!!
That's crazy that it doesn't have programming for charge voltage. The lithium setting should be 14.6v charge and 13.8v float. Is there a user program setting?
If you dont mention top balancing of cells you shouldnt be making videos about charging LiFEPO4 batteries. Calendar aging will impact battery life more than full charge discharge cycles. Yet another uninformed person making pseudo expert tutorial videos that lack the knowledge to do so.
yeah my battery like its around 12v at the lowest and 13.333 at the highest ive even charged it up to 13.5v and it drops back down to 13.3 no matter how long i charge it for so yeah thanks for sharing
I have a ecoworthy system 8 lifepo4 batteries but the batteries won't charge above half way well sias half way on panal as in two bars but I'd say not even half way what am I doing wrong
It sounds like you don't have your charge controller set correctly. Charge current setting should be at least 14v if all of those batteries are wired in parallel.
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It's not just about AH remaining, it's about balancing the batteries. I'm now sitting at 61kw of LiFePo4. I was charging at 3.45v per cell. It worked well for a few months but I noticed when I get low on charge that my packs will get up to 300mv difference. I've increased charging to 3.50v per cell and the issue went away. You want to get into the steep part of the curve but not max out. I run two houses full time with these batteries. For those with pre-made packs it's 14.0v bulk 13.4v float, 28v bulk 26.8 float, or 56v bulk 53.6v float
Thank you for the information and the comment.
Hello, just wondering which cells you have and the BMS?? Some have a setting to equalize when charging and when you turn that off it equalizes all the time and does a better job of keeping the variation low.. I bought 2 with active balance that does up to 2 amp transfers between cells..
You only want balance to start when the cells reach 3.45v/cell. For my 24v system I still use 28.0v bulk, 26.8v float, balance start at 3.45v/cell. I'm using eve cells sold by Gobelpower and 2a jk bms
I know you watch Andy at Off Grid Garage and he has done a deep dive on this subject. He initially set his charge voltage approximately where you were at (3.4--3.45 per cell). I believe he has since changed that to a slightly higher value due to the balance function of the BMS.
Everything you have presented here agrees with what others have found out about this chemistry. LifePo4 is so interesting and makes one re-think everything we learned about batteries (lead acid) over many decades.
Andy's channel is great and I watch it all the time! Thanks for the info and the comment!
Thank you for the information. You definitely want your batteries to have the longest life possible. Thank you for the video!
I too have watched most of Andy's vids on LifePo4. He did some extra vids after commenters mentioned balancing would be easier with slightly higher voltage. His tests I believe did not confirm this. I think he sticks with 3.45v per cell(13.8) and recommends an active balancer over the lower amperage passive balancer built into most BMS. It's a very interesting topic. I bought the same tester/discharger/charger. Pity it's only 5A charge at 13.8 odd volts. I now parallel charge a 10A and 20A charger and finish off with the EBC unit as its programmable to stop at a set current. Great unit to have for around $100.
Im using an EPEver 40 amp charge controller on my 200amp 12 volt Ampere Time battery. I had it set to Bulk 14.4V for 30 mins yesterday and Float 13.6V. Today I turned it down to 14.2Bulk 30 mins and 13.6V Float. Im going to turn it to 14.4V Bulk once a month so the BMS balances the cells once a month. Im on the fence about Floating at 13.5V or 13.6V. The only load is a mini fridge. Its plugged into a Xantrex Prosine 1000watt that Idles at 1.5watts in Power Save Mode and the compressor kicks it out of that mode 1/3rd of the time to run the compressor.
@@garyenwards1608 You don't want to float lithium batteries, it's not necessary, as we are not at risk of sulfation since Lithium is not a lead acid chemistry, and you risk shortening the life of the battery, as your still putting current into the battery. If you can't disable float stage in your charger, then set the voltage to something lower than the resting voltage of the LFP battery.
Thanks for this.
The float voltage needs to be at a level where your solar panels will kick-in to provide power rather than the batteries.
I use the "Equalize" setting on my charge controllers to occasionally ensure the BMS in the fully charged batteries will have the voltage to run its top balance program
Thanks for the comment.
I was just thinking of trying this on my CC. What type of CC are you using? Does it Equalize once a month? I dont see a schedule or time adjustment for the Equalize setting on my EPEver CC. Im using an EPEver 40 amp charge controller on my 200amp 12 volt Ampere Time battery. I had it set to Bulk 14.4V for 30 mins yesterday and Float 13.6V. Today I turned it down to 14.2Bulk for 30 mins and 13.6V Float. Im going to turn it to 14.4V Bulk once a month so the BMS balances the cells once a month. Im on the fence about Floating at 13.5V or 13.6V. The only load is a mini fridge. Its plugged into a Xantrex Prosine 1000watt that Idles at 1.5watts in Power Save Mode and the compressor kicks it out of that mode 1/3rd of the time to run the compressor.
@@garyenwards1608 You could set float to 13.4V and be below an active state of current flowing into the battery, assuming it is indeed fully charged before hand. Then, there's no risk of low current, over charging of an already full LFP battery.
@@s.mendez7160 Thats a good idea ive been thinking about doing that. Thank you for the feedback
@@s.mendez7160 What would you recommend for a boost voltage and duration? I've been thinking of elimination the duration and just setting a voltage of 14.4 but i have a few EP ever charge controllers all hooked to a single battery
Its only going to drop back down to that voltage anyway, so it makes no sense to charge the cells over 3.4v or the pack over 13.5v Anything else is little to no gain and detrimental to the battery. The only time you want to charge the battery to 14.6 < is if the cells are out of balance which is rare for a battery thats in good health. To keep it in good health is to not over charge it . Good video
Thanks for the comment and info!
Each cell can be equalised with a victron smart Bluetooth mppt.
@@simonpepper9721 Right! and that is where you should realise if the cells are new or depleted, deteled
@@simonpepper9721 If your cells come in a plastic , or pre made box , then its all bad news, wheather you realise or not
You should bring them up to 14.4 at least once a month to balance the BMS.
Thanks for the comment.
....for me that's easy, I use the same battery, a TimeUSB 50 ah and a Renogy solar charger... just set the Renogy on LI default about once a month.. quickly goes to 14.4...but on user setting 13.8-14 for the rest of the month... I use mine for a solar powered a ham radio setup so absolute max AH available is not critical.
13.7 or 13.8 is a good charge voltage for a 4 cell LFP battery. You should have at least 3.4 to 3.45V/cell for balancing, not below. If you don't need to balance keep it at 13.6 ... 13.8V thats absolutely enough. On the other hand, you could also go up to 3.5V/cell without really harming the cell what so ever, but above begins the stress level.
Thanks for the info and the comment!
Thanks for your test information.. I am building a monster dual 15kw 48v battery for 30kw at a top charge of 58vdc using 17 LiFePo4 EVE cells and have been watching quite a number of videos to basically learn the craft.. Still trying to settle on the top charge per cell between 3.4v and 3.5v with a bottom of 2.9 to 3vdc.. My 8kw inverter can accept an input between 40 and 64vdc so if I keep the voltage higher it will make more power for less heat because as the volts get lower the amps get higher and amp flow is heat.. Bought 2 JK BMS that are the slightly older version but have the 2 amp active balancer which allows the bypass of the stringing cells and charging them to 3.65v to get balanced cells.. Instead I will check all cells to make sure they are similar 3.0 to 3.2 near the bottom then assemble the pack, setup the BMS and controller and gradually walk the battery to 3.6v per cell to get 61.2v over a couple of days as the active balancer levels out the cells.. Once top balance is achieved I will back the voltage down to that undecided operational level.. As for the float voltage from the charge controllers I am thinking that I will set it just a couple tenths of a volt lower so during the day the solar panel production once the battery is full will handle as much of the loads as they can and to prevent micro charge cycles..
Your plan looks good. Getting all the cells to top balance is key. Enjoy your huge setup! Thanks for the comment.
Note that the vendor specifications for a lot of these fly-by-night brands are just plain wrong. Often these vendors don't even know how the BMS in their own battery is programmed.
For LiFePO4, if you don't have control over the BMS settings, you generally always want to charge to 14.2V (3.55V/cell). The reason is not to try to get the battery to 100%. That has nothing to do with it. The reason is that the BMS may not start balancing the cells internally at a lower target voltage and if the BMS's balancer is not operating, the individual cells will go out of balance and some of them will wind up at 3.65V (the BMS cut-off) despite you having that lower target voltage.
Because of this, 14.2V is generally the best choice. 3.50V/cell (14.0V) is also a fairly safe bet. But lower than that is not a good idea.
i.e. you can wind up putting more cycle wear on the battery with your lower target voltage than with a 14.2V target. So this is why you pretty much always want to charge to 14.2V. Don't worry about cycle life, charging to 14.2V won't hurt the battery. Discharging the battery all the way to BMS disconnect will put far more cycle wear on the battery than charging it to 14.2V will. Like an order of magnitude more.
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Now, for float, the float ALWAYS must be set to 3.35V/cell to 3.375V/cell. That is, 13.4V to 13.5V. NO EXCEPTIONS! This is the voltage range where load support can be provided without discharging the battery (for example, in a solar application), while at the same time not being so high that the battery continues to charge while sitting at that voltage. This is also the voltage range which puts the least amount of wear on the cells from sloshing around as the load changes and the charge controllers try to match it.
If the float is set higher it will continue charging the battery, ultimately overcharging it. If the float is set lower, it will discharge the battery and also the sloshing from the load-following the charge controllers do will put more wear on the cells.
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If you are still worried about charging the battery up to 14.2V you can always take a little off the top after charging is completed by putting a load on the battery for a minute or two. If the battery is permanently connected to an inverter or a system that always has some load, even if only very small, you don't have to worry about it at all because the battery will more or less immediately drop to near the float due to that load, after charging has stopped.
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In terms of attempting to charge to a particular SOC below 100%... its a bad idea, because the BMS will generally not be able to balance its cells internally if you charge to a lower SOC.
For discharging, if you can control when to turn off your loads it depends massively on the amount of load. For light loads (up to around 0.3C), a 12.0V floor gets you 95% of the battery. For heavy loads you can go lower.
The issue with discharging is that discharging all the way to BMS cut-off, repeatedly does an ORDER OF MAGNITUDE more damage to the cells than anything else you could possibly do to the battery. Its ok to do it, it won't destroy the cells, but you are putting a lot more cycle wear on the cells by discharging them that low.
Also, if you fail to charge the battery in a timely manner (like fir a week or two) after it has been discharged to that degree, you risk the cell self-discharge from taking the cell voltage into territory that will significantly damage the cells.
LFP batteries are far, far more likely to be destroyed by over-discharging them / letting them sit while discharged, then by "overcharging" (holding them at a charging target voltage for days or weeks on end). Holding the battery at the float 24x7 is fine, but in that case choose the lower-end of the float spectrum. 3.35V (13.4V).
And in solar applications you generally don't have to worry much at all due to the cyclic nature of the charging and discharging.
-Matt
Perfectly stated!
Thank you for spending the time to give us all of that great information!
Notice that some vendors that claim1.0C as the charge rate in their instructions now recommend 0.2C on a regular basis and a max of 0.5C. They learned from claims and angry comments about early failure.
Hey Matt. I have a 100 amp lipo4 battery with BMS. My controller only has a float voltage to set (no bulk charge). I always have a fridge load running. What should I set my float charge? So confused. Thanks
@@dandunlap9111 I don't think I know of any controllers which only have a float setting but not a bulk (or absorb) setting. So the first thing to do is find and read the documentation on your controller very carefully. If you can't set both parameters then you'll want to get a controller where you can.
That said, in a solar application where the battery is being cycled daily and charging drops off when the sun sets, you can temporarily just use the charge target for your float setting. LiFePO4 can tolerate being held at its charge target for long periods of time. But it isn't an ideal situation to be in and you will want to rectify the situation.
-Matt
Great job on the explanation and the visuals., really helps
Glad it was helpful! Thanks for the comment.
Yes, a good way to not stress a battery.
Thanks for the comment.
The LiFePo4 cells are far more durable when stressed at the top and bottom than the older Lithium Ion formulas so charging is less critical but as he showed you gain very little when pushing the limit..
Yes, the chemistry should give LIFEPO4 an edge if build quality is the same. But we have not had consumer grade LIFEPO4 cells on line long enough to draw a valid conclusion.
super useful thank you, this taught me so much about how my new lifepo4 battery works and what to aim for on my charge controllers and importantly why its the case. The graph was ideal way to understand it. subbed
You're welcome! I'm glad it was able to help you out. Thanks for the sub and the comment!
Good Revision, I set mine to 27.6 volts.. I just got a new MPPT,
Happy with Y&H 100A MPPT Solar Charge Controller 12V 24V 36V 48V Max 100V Lithium...30 bucks cheap but nice big screw fixing holes...3 x 375 working fine. I tried expensive Victron but 100/20 but kept blowing fuses even with 1 375 panel. So, I returned it. Think I am set for summer now.
That's excellent! I can't wait for the summer sun to return. Thanks for the comment.
I emailed eco- worthy on advise for programming victron mppt to work with one of their 12v 280ah lifepo4 batteries. They sent me a response but it dont make sense it goes against advise given in videos like this ..
"We recommend adjusting the charging voltage and float voltage to 14.6V. This is a common setting for LiFePO4 batteries to ensure optimal charging and battery longevity".
This is because of what is a ‘common industry convention’ or concurrence as to existing charging device algorithms …’Implied compatibility’ in this way is mere marketing that sells batteries - Vendors are incentivized to tow the line…
You really got that one off... You missed the whole Bulk, Absorption and Float steps.. Bulk will shove alot of amps into the battery until it's at about 90%, then it will go into Absorption until it reaches the needed voltage for the bms and equilization (14.2 - 14.6), at that point it will drop to the Float voltage which is usually 13.6-14.0... Then the charge controller will maintain that voltage. Under charging your batteries like that is going to backfire on you eventually... But good luck..
This video was intended just for float settings on a 12v lifepo4 battery. Not for how to set a solar charge controller. Thanks for the comment.
i already lowered my stats but still i need to find the perfect timing cycle of all this because the lower i go the faster it goes and victron has the potential timing of this cycle... still testing my setup .. good thing is i never found my shed in error.... keep up
Thanks for sharing and the comment.
I just charge mine to 80% & it’s fab 😊
Thanks for the comment!
Useful findings which I need observe with 24V
Glad I could help. Thanks for the comment.
If we have (4) 12v 228ah batteries in parallel, what should the AC charge be?
Wow. Any AC charger would be a trickle charger for a bank that size. I would get a couple 50a chargers and connect them both up.
Fantastic. Needed this .
Glad it was helpful!
Thanks for the valuable info
My pleasure. Thanks for the comment.
The problem with charging with low voltage is time you are losing the potential from the solar. at 3,4v it vill fill up but it vill need to absorb for hours pulling minimal current meaning the MPPT is just idling the solar panels
That's true, but we are also talking about the last 1 - 2% of the capacity. I would rather get more charge cycles than that last 2%. Hope that makes sense. Thanks for the comment!
@@OffGridBasement it is much more than just 1-2% as with lower charging voltige the power going in tapers off really early and you can lose 1h+ of solar
@@OffGridBasement with 3,4V you are reducing charging as early as 50-60% SOC depending of charging current using 3,5-3,55v is a better option as the dropp in charging power only happens around 90% SOC and is much smaler.
I enjoy your informative video a lot. I've been thinking of building a diy 12V portable power system just to learn possibly using a 1500W inverter and 2 or 300ah battery. My question is what amperage charger should I buy 30A, 40, 50A?
Lifepo4 batteries like to charge at 20% of the total ah capacity. 20A charger for 100ah battery... 40A charger for 200ah battery and so on. Anything that is slower is totally fine. Hope this helps! Thanks for the comment.
According to the Jackery web page 13.6/3.40 rest voltage is 100% charged
Any LiFePO4 battery can be fully charge to 100% if held at any voltage above the float range for a long enough period of time. Generally that means 3.40V/cell or higher. However, the amount of time you have to hold the battery there is variable. If you stop the moment it hits 3.40V/cell (13.6V), even after waiting for the current tails off, the battery is probably not fully charged.
The main problem with using low voltages like 3.40V as a target is that the BMS probably won't balance the battery's cells internally at that voltage. So you wind up doing more damage to the battery rather than less as the cells go out of balance.
For example, an out of balance battery held at 3.40V might have cell voltages of: 3.35V, 3.35V, 3.30V, 3.60V.
An addition problem with using a low charge target is that at a high charge rate (e.g. 0.4C+) you will reach that target long, long before the battery gets anywhere near 100%. Like you'll hit it at 70% or even 60%. And with the current tail you might reach 80%.
Also, once the cells have gone out of balance you can start to lose capacity at your lower target voltage because some of the cells will not reach anywhere near 100%.
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If you have full control over the BMS settings, you CAN charge to a lower voltage by ensuring that balancing starts at e.g. 3.40V and then using a 3.45V charge target. However, this only works well in warmer temperatures. In cold weather you definitely want a higher charge target, regardless.
Most batteries that do not give you access to the BMS don't balance at that low a voltage and you need to charge to 3.50V/cell or 3.55V/cell (14.0V or 14.2V) to be certain you are engaging the battery's internal balancer.
-Matt
@@junkerzn7312 good stuff
Thanks for the info and the comment.
my lifepo4 batteries are always stuck at 27.6 you think that is a problem? Its because its hooked to a ups taht is used to a lead acid
For a 24v battery setup that is just fine.
@@OffGridBasement sweet I noticed also near by at my local college surplus they are selling 30 APC the 5kw version pure sine wave for 500 bucks, seems a bit high going to see if it comes down but I bet those little bad boys are amazing form the looks of it, I think they are low frequency too, I refuse to use a HF inverter, cant stand them
Hi sir
I have Lifpo4 16s, It's connected by bms cable
My battery wont charge until its 95%
I believe its because the float charging volt is low
I dont care about the 5% i dont need it
But im worried about my battery longevity because it keeps charging between (soc 100% and soc95%)
Multiple times through the day what do you suggest
The charge controller shouldn't go back into bulk charge after going in to float unless you are using more than your solar panels are producing. Does the charge controller have a re-bulk charge setting? If so, change that so it's lower than the float setting.
@@OffGridBasement
No sir
I dont have re-bulk
I dont know what's really happening when i had a voltronic inverter my battery at day time was 100% al the time
Then i switched to deye inverter now the battery charge to 100% then discharge to 95% then 100% .. 95% etc..
I don't know why this is happening because i have more than enough power from the solar panels
If u have email or Whatsapp number i can send for you some photos
My UPS floats @ 13.8v. I wonder how many years a 12v LFP battery would last held at that voltage constantly.
Since that really has nothing to do with cycles, I have no idea! Probably many many years! Thanks for the comment.
@@OffGridBasement I found this comment which suggests you can get away with a 13.8v constant float:
ruclips.net/video/4SCgXrl-rqg/видео.html
"I've mentioned this a few times before: I've got half a dozen UPS units using LiFePO4 cells that are charged 24/7 for 5+ years at a constant voltage of 3.45v per cell and they are fine. There's no way you could overcharge them at 3.35v per cell."
It's my understanding that for long-term storage.A lithium battery likes fifty percent charge.
Lithium's don't need float voltage, that's for lead acid chemistry to prevent sulfation. @13.8V you risk shortening the life of the battery, as your still applying a small flow of current into the battery. Either change the float voltage to below the resting voltage of the battery, or figure out how to take the charger out of the circuit till its time to recharge the battery.
@@s.mendez7160 another RUclipsr reportedly has already been doing so for >5 years with no damage, with several UPSs.
I partly agree. But once in a while you should slowly charge to 3.65V / Cell to give the balancer a chance to balance out all the slightly different cell voltages. That is only possible between 3.42V and 3.65V outside the flat charge curve area.
Those cheapo batteries mainly have small passive balancers which need time. Only large 15kwh packs have active balancers.
Thanks for the info and the comment.
Far too much emphasis on higher voltage & balancing, if the pack of cells are in series and identical they regulate themselves people get carried away with the whole balancing idea. Many people don't use a BMS and cycle 3.1V - 3.45V which is around 20 - 80% SOC and they work just fine. Balancing at higher voltage with a BMS is just stressing cells more than necessary and shortening their life. Better to concentrate on keeping the cells below 30 C for max cycle life. Compressing is also way overrated perfectly normal for cells to bulge a little when charging, space them out 5 - 10mm according to busbars and if they swell and touch put a piece of thin insulator between when discharged so they can't short out, cereal box cut to size works fine.
Thanks for the information and the comment!
I agree to a point. However, over many months the cell imbalance will get greater and greater.
lol hippie lol just messing with yeah brother i have long hair but you do look better with shorter hair so thats good thanks for sharing
Thanks! I figured I would grow it out until I remembered I hate long hair in the summertime!
Why do the wires come out of the top instead of the bottom and under ground in conduit..
I honestly don't know what you are referring to.
@@OffGridBasement You don't see the wires coming out of the top of your outside battery enclosure, it's probably the only visible wires in the video..They should come out of the bottom, run into under ground conduit and run into the house..
The only person I`ve found who HAS THE MPPT CONTROLLER I BOUGHT says..."There` s a way to set the voltage for lifep04 and all but gee I can` t remember what to do..." And he USES IT!!!! GOD DAMN! Now I have to buy another one and HOPE it comes with an ENGLISH INSTRUCTION MANUAL!!!!
What is the make and model of the CC?
@@OffGridBasement OAE 60 amp mppt 12, 24, 48 watts & 150 volts. The manual is badly translated. It has "lithium ion" setting and the manual says FLOAT is the only way to adjust the charge voltage. It` s running set for 12v battery, lithium ion type, 13.80 float voltage with two 190w HQST panels in parallel. Until I figure out whether it`s charging the battery I`m not connecting my larger, shorter cables or using series. I can`t afford test equipment. I`m running a 400w air conditioner....watt meter connected between the AC plug and inverter...and eventually I`ll be able to tell if the wattage on the mppt is going into the battery because I started with 3.3 kwh of the 300ah 3.8 kwh battery charge and reset the watt meter.
@@OffGridBasement 12, 24, 48 volts. I can`t think from total frustration. I can` t type or think right now. It has these numbers in product description. My brain is in knots from this garbage.
@@OffGridBasement I have the following....(Farpoint Farms CH) Long term Review of The MPPT Onesolar 60 Amp solar charge controller.
My lifepo only goes to 12.6.
A lifepo4 battery should be fully charged when it gets to 14.2v - 14.6v.
@OffGridBasement mine comes out of a companion Fridge.
Somehow you talk like a mechanic. Not an electrician.
That's because I'm neither! I'm actually a computer systems administrator!
Is there a simple, affordable, easy to program charge controller? PLUG AND PLAY FOR A 12v LIFEP04???? The only settings in mine are battery type, battery voltage, and float voltage. In the manual it says the LITHIUM ION setting only has float voltage and it defaults to 13.80. The Chinese manual is INFURIATING!!! I`ve wasted so much money and time for over 2 years and I STILL DON`T HAVE SOLAR because I can`t afford the "Will Prowse" instructions!!!! Solar forums are like a technical JACKOFF SESSION of confusing nonsense and nobody uses 12v systems so poor people are SCREWED trying to get answers. I simply want to run a 400 WATT WINDOW AIR CONDITIONER and not destroy a 300ah Ampere Time battery using my solar panels!!!!!!
That's crazy that it doesn't have programming for charge voltage. The lithium setting should be 14.6v charge and 13.8v float. Is there a user program setting?
If you dont mention top balancing of cells you shouldnt be making videos about charging LiFEPO4 batteries. Calendar aging will impact battery life more than full charge discharge cycles. Yet another uninformed person making pseudo expert tutorial videos that lack the knowledge to do so.
This video was about float values, not charge/absorption. Thanks for the comment.
yeah it took me awhile to figure all this out
me too. It seemed to just "come together" after reading and watching RUclips videos for the 100th time.
yeah my battery like its around 12v at the lowest and 13.333 at the highest ive even charged it up to 13.5v and it drops back down to 13.3 no matter how long i charge it for so yeah thanks for sharing
I have a ecoworthy system 8 lifepo4 batteries but the batteries won't charge above half way well sias half way on panal as in two bars but I'd say not even half way what am I doing wrong
It sounds like you don't have your charge controller set correctly. Charge current setting should be at least 14v if all of those batteries are wired in parallel.
@OffGridBasement ok so how would I set that please sorry if I sound like an idiot