Why compression will not extend battery life (something else kills your batteries).
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- Опубликовано: 31 июл 2024
- Many people are asking me frequently why I don't compress my batteries to extend their life. The datasheets of the EVE cells show that compressing makes a difference in cycle life.
In this video, I will explain why it does not matter if batteries are compressed, clamped or 'fixtured' or not. There is another enemy which actually kills the battery before they reach their cycle life: calendar age!
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Yes exactly, and I'm so tired of arguing this 😂 I have been mentioning the calendar aging factor in my recent videos as well. I am glad that people are starting to figure this out. If I want a lifepo4 to last longer, just keep it cooler and make the pack larger. That's it.
I'm cycling 30kWh grade b packs with a small gap between them and it works great.
I also cycle to 100% and down to 0%. I don't understand why people try to change this. Especially for solar. I think it's based on nmc studies where a massive improvement can be found. Not so much for lifepo4.
And guess what! At the end of these cycle life estimates you show, you can still safely cycle them! I have used lifepo4 cells with 60% capacity (old byd packs a few years ago) and they worked fine!
Ya know Will, your forum is really where this compression thing started. Just saying... 😂 🙃
@@LithiumSolar I disagree with my forum members all the time. But yes indeed.
I was thinking of doing it but never got around to it
Oh hi Will, I shouldn't be surprised to find you here XD
I think it's great to have all these people out there trying different things. That's what the DIY scene is all about. And who knows, maybe someone discovers something which can help us all. Would not be the first time 😏
Preach it, Andy! By the time our LFP batteries are down to 80% we'll be chomping at the bit to buy the next tech that's 4x as good at half the price.
Thanks Andy, good info. Appreciate you taking the time to chart this all out and explain different factors. My batteries are en route from one of your recommended suppliers and I've been pondering compression.
Finally! Somebody who looks at cycle life the way I have been. I’ve been saying for a while that my batteries will outlive me .
I’m currently only use 20-50% of my batteries power per day for 6-8 months a year. The average draw on the batteries is 5-10amps with short spikes of 50-75amps.
Ha, they will live forever with these small currents. If you keep them cool 😉
I think you mean the batteries will outlive you!
@@grahampicman8286 yeah, I screwed that up lol
@Off-Grid Garage you hit the nail on the head. Cooling is the issue where you are in OZ. You lose about 25% of the life at least due to temperature alone. If you cool them and compress them they will last for ever
Good one again Andy.
My Winston 400Ah cells are now over 6 years old. With simple capacity tests, I’ve seen no NOTICEABLE or measurable degradation so far.
8 years here on my old Winston cells. Still going very strong.
is there any any cells bloated?
I have Wisnton 100 Ah WIDE and TALL from 2013, and they perform OK, without BMS, only monitorinig cells voltage, 0.000 mm bloated.
@@angelabrillajr.1209 winston ones have that beefy outside cell.. they even heavier... didnt ever figure out in any video of em mention any seen bloat
Hard Facts. Well done Andy and you have earned everyone your donated SPATs and many many more to come. Thank You
As usual, that's what I was wondering! Excellent work and happy calibrating!
Thank you for a very good video. You really explain this perfect. I’m using two electrical vehicle battery packs, and they are already compressed as you mentioned, so I just re-configured the cell configuration and then I use the module boxes again, just to have everything well organised and also because that I’m already know that they have the right compression on them. In normal cases I had done it just like you did with your pack. Thank you for a great channel.
Greetings from Sweden.
Thanks Andy.
All that info has answered so many of my questions. I cant wait till my batteries land in Auss, it's getting so exciting.
Great, you will be perfectly set and can start right away. It is in deed exciting!
i'm totally with you with the "batteries needs proper ventilation" part. In my opinion, stressing (overcharge/discharge/high c ratings etc.) batteries eats its life faster than any other factor, building a bigger energy storage can easily solve this factor.
I agree with your conclusion regarding the practical advantages of compression. I still fix the cells in place though (not really compress, just fix so that they cannot move), mainly because I would like to avoid putting stress on the terminals.
I am aware that it is possible to use longer busbars and have gaps between the cells and therefore better cooling. On the other hand, such battery pack is difficult to move around.
This is how I did it too, not compressed but set up to prevent expansion
Great information as always and I completely agree with your assessment. The compression won't be the determining factor for cycles on the batteries.
The problem I have is that this is all academic at this point. There is not enough people that have had these cells in use for long enough for us to really know how long they'll last and how much of a difference compression/no compression and other factors make. I know of a few folks that have had lifepo4 for 10 plus years but they were using the plastic case CALB or Winston cells, I don't think the aluminium case cells have been around that long.
Unless someone has clear evidence that compression is harmful to the cells, I just can't see any reason not to do it. Preventing the layers in the cell from separating has to be a good thing, and may help with calendar aging too. My cells were a big investment, and if the ~$30 of materials and one hour of my time to set up compression gains me even just one year of use than that is well worth it.
As for the assumption that there will surely be much better batteries available, for much cheaper, by the time these cells wear out, well, that is just an assumption. I sure hope you guys are right, but there is no way that is guaranteed.
exactly....the manufacturing plant with many years of experience do not print these specifications for no reason...
resources were used in the production, which is valuable. Even if you don't use the life of the cells, someone else might. I think we should be sustainable everywhere 👌👌
But the resources would be used in any way, regardless if the battery lasts 5000 cycles or 7000 cycles.
Wow, these things really are long lived! That was a very well thought out presentation.
Thanks for the feedback.
Spot on, I did the numbers for myself too, and decided that by the time I wear out my cells, I will probably be dead. But even if I did wear them out in 5-10 years, there will be a significantly better battery available to replace it, at a significantly lower cost, with better performance. Compression/fixture is a tiny gain when we could be spending our time and money on other bigger gains. The $100+ worth of materials could buy us another solar panel, or better wiring, or lots of other more beneficial things.
And this right here, is a great example of why the planet is fucked.
@@StartledPancake perhaps you can be a bit more expressive rather explicit. Your comment means absolutely nothing because it has no context. The swearing is not necessary either.
So do explain to the rest of us where your vague hatred comes from. There's a more than obvious argument that the planet is @#$%^ because of people like you who chime in to voice an irrelevant point of view, without backing it up whatsoever.
If you don't have something of value to offer, just don't speak at all.
And finally, when my cells wear out, they will have done their purpose, regardless of if I use them harshly for 5 years, or gently for 20 years. When that time comes, the materials inside those cells will be reclaimed and reused in whatever the most appropriate way is at the time.
@@PowerPaulAu You know exactly what Im talking about, so there is no need to be more explicit. Lithium mining is one of the most environmentally damaging mining processes on earth and the metal itself is in incredibly short supply. There is as yet no economic way to recover lithium from batteries and even if there is, that process will be environmentally damaging also.
People shortening the life of their, highly impactful, batteries because they cant be bothered to spend an hour making (or buying) a compression set is shameful, there's no other way to put it.
@@StartledPancake you're very wrong about the recycling of the components of these batteries... Go get some up to date information.
It sounds like this isn't the right place for you to be either, there's Lithium discussion and use every episode. Go where you'll have something useful to add, because it's not here.
You don't have to like me or what I do, but it doesn't entitle you to go on a rant about it. Be gone little troll.
@@StartledPancake That's a bit of a Utopian view, considering we as a human race are still struggling to get out of the coal/oil age. Can we at least agree to leave fossil fuels behind before we march headstrong in to solar powered battery efficiency issues?
This is great info! I see my first battery built with cutting boards at 1:24
It was fun to figure out the compression thing, but yeah, I always wondered about longevity. In my case, these go in van campers which probably see a few dozen cycles a year at most… Even without considering the temperature aspect, compression vs non-compression was a difference of 40 years of use vs 80 years of use! The van that this compressed battery went into is already 36 years old, and we’ve done less than 10 cycles over the last year 😅
Good stuff!
Thanks for your feedback. I would probably compress the cells in a camper van due to the vibrations and movements. I also would use flexible busbars for such an environment. Just to get the full 80yrs 😁
This is the Video Ive been looking/waiting for.. Thank you Sir
You're welcome
Excellent stuff. You've answered more great questions again, thanks.
Thanks David, much appreciated.
Agreed.
Thanks Andy. I have had so many people tell me I am ruining my cells with compressing them. Keyboard warriors.
Hi Andy! Thanks for adding the very important ingredient "REALITY" to the soup :-) That will enable people to focus on issues being important during their actual life on earth. Finally it is a race of calendar aging between battery and the owner ... :-)
Nevertheless I confess to have compressed my battery pack very mildly. The reason ist that now I can use those braided bus bars form aliexpress that will not fit otherwise. Obviously the chineese manufacturer of those braided bus bars based the disign on nominal dimensions of the cells. Well, mild compression makes the equation fit - along avoiding any mechanical stress on the poles during battery life.
Very helpful, thank you! No need to spend tons of money for compression 🙂
I would like to see Andy refurbish the old Eve 280ah pack, and see how the cells have faired.
Thank you so much for putting this discussion into the right comparativeness.
Lot's of people have asked why I don't compress, so I can now send them the link of the video instead of repeating myself 😊
@@OffGridGarageAustralia Sneaky. 😉
Thanks for putting this out, we do not run compression on our banks either. My thought was the same that by the time we no longer have usable capacity left we will want to replace with new technology or no longer be living.
Yeah, it seems like the batteries could outlive some of us. Me included 😊
The data sheet states that you should replace them when they're at 70% capacity.
Awesome thanks, I have been trying to keep my Batteries at a 100%. Need to start using them
Amazing analysis Andy, thank you
Thanks Andy, a bit of simple logic for all of us techno-geeks 😇.. I could not agree more.
Thanks Chris. So many people have said, I have to compress the cells. Well, it's really not a must as we can see...
I chose to do a light compression simply to hold things together in my school bus conversion. I didn't want the terminals getting a bunch of stress from the cells moving around a bunch.
Yes, that makes sense. Do you use flexible busbars as well?
@@OffGridGarageAustralia no, i figured that since prebuilt batteries generally don't use flexible bus bars, and since my cells are held snugly together and their box will be securely fastened to the frame, it shouldn't be necessary. Here's to hoping I'm not wrong.
Andy, You rock! Thanks for bring us into the practical world- it's called wisdom, and you speak it fluently. (-:
I wanted to give all the advantages I could to my investment. A squeeze box is inexpensive. It may have a marked advantage as a fight against calendar aging. A lot of all these projections are exactly that, a projection since obviously time will only tell. I do believe we will see failures of terminals and internal damage to the “jelly roll” due to expansion and contraction of every cycle. Flexible buss bars may help with the terminals but compression may help the innereds. Again, time will tell. Andy did make a point about a small gaps between the cells for cooling. That’s definitely a negative with tight fitting compressed cells.
A thin malleable heatsink between the compressed cells could provide some cell temp reduction. A sheet of aluminum extended beyond the outer cell edges comes to mind... just make sure there's no chance of it coming in contact with the terminals or busbars!
i totally agree with Karl Jensen ...>>>>>it would seem to make good sense to do the inexpensive compression jig...an inexpensive improvement...and keep all components, batteries, inverters charge controllers in a climate controlled space to increase their life span... the false assumption that there will be cheaper batteries in the future.... because the attempt to increase the life span cycling as the manufacture specification sheet says is the better path /more prudent path to go down...ignoring the manufacture spec sheet is just fine if you like to waste your money....32 cells cost $2900 delivered in September 2020... they cost $4300 in October 2021 and in the present year 2022 they are now close to $5000 dollars... if you think that inflation is nothing to the increased cost of LiFePO4 280Ah cells and promote doing nothing to protect or preserve this huge investment....a fool and their money soon part ways....the fixture should contain them with similar pressure near the top where the busbar interconnect are and toward the bottom so the busbar connection ANGLES do not change...heat is caused by poor connections. flexible bus bars are a possible partial solution to part of the design problem... the fixture is the keep the thin-walled RECTANGLE SHAPED ALUMINUM CASED PRISMATIC cells from bulging and allowing the inner plates from distorting and sagging... (the so-called "jelly roll) if there is someone who actually has any real scientific basis to say do nothing is the best route over making an effort according to the scientific specification sheets of the manufacturer then provide real data.... AGAIN IT IS THE BETTER ROUTE TO DO SOME EFFORT THAN DO NOTHING....
@@pilgrimvalle
Great minds think alike. 👍 I wouldn’t change a word. No rebuttal. Eel battery distributor told me that his source was quite adamant about the need for compression. Just short of saying mandatory.
"Just use the Heck out of them". Enough said.
I have 32 cells that I use between 20% to 50%, depending on the sun every day. I didn't buy them to sit on a shelf and look pretty. Thanx Andy for the commen sense approach on Life. 🤟🤟
Go nuts! Really. They can take it.
Great to get another point of view on this subject 👍
You bring up some very valid points!
This video is an instant favorite for me.
Thank you!
Andy, I think you're spot-on with the cycle counts. Great calculations and appreciate the information sharing! One thing you haven't touched on though is stress put on the terminals. Many people are using solid/rigid busbars that come with the batteries. These batteries expand and contract naturally - maybe a millimeter or fraction of a millimeter. Don't you have any concern regarding the stress this movement may place on the terminals from the solid busbars if the cells are not "fixed" together? We can agree the amount of movement is super tiny; however, compounded over many years - could result in premature failure. Or maybe I'm just overthinking it? I'd love to hear your thoughts. Of course, this can be negated by leaving space between I suppose...
Thanks for your comment. There are two types of expansion/shrinking, one coming from the pure temperature change, the other from the swelling/contraction of the cells during charging/discharging.
I think we can disregard the temperature caused expansion as this will be very minimal (but it could still contribute to mechanical stress if it adds to the force caused by swelling due to charging).
The thickness of the cells stated in the datasheets is 72mm +-1.0mm under 300+-20kgf. Obviously this is just the production tolerance for the aluminium case but interesting they show this figure under compression! I have yet to find a method to measure the actual swelling/contraction with such a precision so it is reliable and reproducible. As you said, it could be a fraction of a mm and I believe this is occurring only around the area where the electrodes sit in the case. So a partial, non linear swelling. Interesting is also that some cells tend to do it more than others which could be caused by (poor) manufacturing processes and tolerances.
I will leave a gab between my cells so they stay as cool as possible and also avoid any mechanical stress when using rigid bus bars.
I believe high temperatures may have a larger negative impact than we can compensate with compression. If you live in a cold climate and can keep the batteries at around 20°C all year around AND compress them, that would be the ultimate best setup to maximise the life of these cells.
Uh, that's a long text now, sorry 😊
If there is a bulge expansion coming from the middle of the cell it can be caused by the highest temperature in the middle. The uppoer and lower parts will then get a gap of air as coolant stream if they get ever really hot under high A.
But considering that below some Winston LiFePo4 owners talked about 6 or 8 year old batteries they use without any complaints and nearly 100% capacity still it looks quite good for me.
Finally: if you do not fix then there might be only additional stress once they start to blow up more than before cause connected with no pressure means always a small gap and marging for expansion without damage. Not to forget 4 NM for the nut is not the tightest and the hole is usually at least 1 mm bigger than the strud.
Might be worth an experiment for one who has 2 big batteries to run both architectures in parallel to make a proof what it is all about.
Not sure if I will do a compression again cause such a 300 kg pressure is for sure a physical stress for all the cells.
But I guess there must be something true cause otherwise they would not have added such specific test and use procedure to gain 6000 cycles.
Thanks for the good work on your channel too.
Hi Andy, great video as usual. Tell u what, I'm going to build my battery using your numbers and I'll make sure I live for another 365 years to see if your calculations are correct :) Nicely done Andy.
love it.....i did some rough math on the cost of material for making a compression fixture and after realized that the money should be spent on more batteries to reduce the stress and get the same result of more cycles. thanks for the in depth talk about this fad.....opps now someone is going to be mad.....lol
You need to simplify. Heck for the cost of a cheap ratchet strap, $3usd and a small piece of scrap 2x6 on each end, pennies
Thanks Arnold. People went mad at me when I started building my first battery. They all said I have to compress otherwise I would damage the cells. But a bit of googling shows, it's really only necessary in certain environments... which is not my solar set up.
you can do it with threaded rods and two wood pieces. cheap
Counter point is what if compression reduces calendar aging?
Haven't seen any studies either way but it doesn't sound unreasonable.
I added mine in a fixture, because why not. In any case, high temperature does have a much bigger impact on cycle life, which is why I have an advantage here: my cells will live forever! ;)
Yeah, but too cold is not good either. 20-25° would be ideal. I'm in this range with mine atm. But it gets colder down here now... Unless you build a climate chamber with constant temperature...?
@@OffGridGarageAustralia Actually, when not using the battery storing it at very cold temperatures (even well below freezing) slows calendar aging. I have heaters built in mine: the case is insulated and it uses a small 7W Polyimide heater coupled with an aluminium heat spreader.
@@OffGridGarageAustralia hmm looks like the battery has enough spare capacity to provide its own local heating if required
I'm in South Africa and get so annoyed when all the RUclipsrs getting obsessed about the low temperature cut off of the bms.
@@guy7gsa High temp cut-off has been pretty much a given for some time. Low temp cut-off was missing for a long time. That's probably why...
I have 7 years on my 900 AH 48v lithium bank it never goes below 50% it's still performing at 96% of its original capacity..
Thanks a lot for sharing. A true pioneer in this field!
compressed or not compressed?
@@jimmy4518
Compressed.
@@TheMFrelly Hey could you show us your set up or maybe where you purchased your cells? Please, I’m new to this and I think I’m on the right track of finding Indy from people that aren’t sponsored 😂
Can you share your charge settings?
Best breakdown on compression on the web.
Just how see it, but thank you!
Hey my bald headed brother.... I appreciate your videos and am building an off grid homestead out here in S.E. Arizona and when I do my research, I always look for the nerds because they actually know what they are talking about... my wife is a scientist so I respect the grind... anyways I am going to be making a video on my updated solar setup and was hoping that you wouldn't mind me posting a link to this video....this was such a rabbit hole and was frustrated with the lack of explanation as to the WHY thanks!
So important! Thanks Andy!!
Merci pour ce partage de connaissance technique et d'expérience.
So it basically comes down to just ensuring that the bus bars don't get stressed by the daily cycling. Leaving a gap does the job quite well. Snugging them up (but not really worrying about compressing them) would also accomplish this. On these prismatics, I would assume that mechanical stress even from light cycling would be a factor over time. The engineer in me wants to snug them up. But as you said... nobody has any real experience with regards to knowing what actually wears out at the 15 year mark. All we have really seen is light bloating from grade B cells, but no cell history to tell us why that bloating might have happened.
-Matt
Thanks, Matt. I missed you here! Great to have you back.
We are doing the experiments for science I guess. There must be hundreds of thousands of installations out there, with and without compression. So really time will tell how they will perform. I'm sure we will hear about it in either form...
@@OffGridGarageAustralia Oh, I'm watching every video! I'm just really busy :-)
-Matt
Nice work Andy 👍
Thank you!
8:58 The insects in the background made this moment even more dramatic :D
No seriously thanks for enlightening me on this topic. Very interesting indeed.
However, I will still build a fixture for my cells, but simply to hold them in place so I can move the battery around if I have to :)))
Great video, and good conclusion.
Great video 👏🏻. I also came to the same conclusion on my own battery build…only without the accurate maths.
I don’t know how accurate the cycle counter on my Daly BMS is but I’ve used 24 cycles in 6 months (including deeper discharge in a cold dark British winter) so even if I were to only achieve 1000 cycles that would be 20 years. And even then still have 80% capacity left.
Like you say calendar ageing will be the death of my battery… a bit like the rest of us 🤣.
Hahaha, yeah calendar ageing will haunt us all!
The Daly counts 100% cycles, so if you do a 50% DoD, you will need to do 2 cycles for the counter to go up by 1. _But_ in my experience the threshold current for the Daly is at ~2.6A, so it will not count anything below 133W on a 51.2V system. Most of the time I'm well below 2.6A on the discharge. So the cycle count on Daly isn't really worth anything in my opinion...
I'm not really worried about the cycle counter, but the high threshold also means that the state of charge is usually way off. Especially when there is no/little sun for a couple of days. The battery discharges continuously without the Daly noting anything. So the real SoC may be as low as 30% but the Daly will show 80%. This shows especially when the sun comes back up. After a short time the Daly will show 100% since the charge current is high. But the charge cycle will last many more hours before the battery is actually full.
All in all I like the Daly as a BMS that does its job of killing charge/discharge depending on voltage and temperature reliably. But for anything more sophisticated (balancing, SoC...) it's pretty much useless. The features are there in theory but not really, since 40mA on a 300Ah battery don't do anything. And a SoC display that is usually way off doesn't really hit the spot either.
Andi thx for that simple but interesting math ….. nice job 👍
Thanks Ben. I was always wondering why people chase this compression so much. I had to do it...
Thanks Andy, Yes you need to step back and look at the big picture.
Yes, so let's cycle these batteries 😎
Simply thanks! Now you are Mr. Mythbuster
Hahaha 🤦♂️
My lil God daughter would call the “Mr Smarty Pants” I totally agree with you 100%. I am a recent subscriber to you channel and I do enjoy all your watched videos so far. They are very informative so I’ve learned some stuffs thanks to you. I have system which consists of a Xantrex 6048 hybrid inverter, 4KW solar panel and an Outback 80A MPPT Charge controller.
Thanks for subbing, Jeffrey and welcome aboard!
What's your battery look like?
loved this. Thanks Andy.
Thank you. Just what I think it could be a point...
Thanks for the video and the informations, I have to deal with some "great" comments because I dont compressed my cells at the first charge....😅
Absolutely right.
Large battery banks will probably die beforehand from calendar aging.
The same applies to liion prismatic cells.
My 30kWh liion powerwall got the original compression again, but more because it's easier to attach to the wall. 😂
Its like one of those things.... Starts the discussion in some places and then even the manufacture is pressured to included in the spec sheet... looking forward for the next thing that will drive more discussion... forced cooling perhaps?!?! 😎 sounds 👍 another option that will drive more discussion and make more $$$$. The ones first catch the bird 😀
Great Video. It is rather funny to try to get more cycles from the cell than you possibly use in the life of the cell.
That's what I always thought. The DIY forum is full of threads of this and people went nuts on constructions for... for pretty much no gain.
@@OffGridGarageAustralia Plenty of knowledge gathered from doing it, including discussions with the actual battery engineers. I wouldn't call it no gain.
@@upnorthandpersonal Yeah, but it's not a recommended or even required method to install these batteries. Like with pouch cells, they give you clear instructions. Here it is just a test procedure and result the manufacturer publishes.
@@OffGridGarageAustralia I don't think I ever claimed that, it just shows a delta between fixture and non-fixture in test procedures. Now, statistically speaking, this also means that the probability of failure is higher without the fixture. How relevant this is in any application is up to the end user to decide.
@@upnorthandpersonal yes, I agree with Up North and Personal....I have 2P8S and 4P8S LiFePO4 (96 cells) cycling of 272Ah and 280Ah in 4 batteries... better to make the inexpensive fixture and increase the cycle potential...😎the end-user needs real information, not mere speculation...
I've build a 24v 105ah Lifepo4 battery for my sailing dinghy, to power the auxiliary electric pod motor. If I take the boat out each weekend and I manage to fully discharge the battery each time. That is 40 years of cycles, at 2000 uncompressed.
I am going to use some filament tape to hold the cells together, like you see in commercial batteries.
Cooling is a great pint and underestimated I think. When you tape your cells together don't forget to have some insulation in between them so the thin film does not rub through an short your battery.
40 years is an acceptable life span for a battery 😁
@@OffGridGarageAustralia already got 1mm rubber between them. I expect to be running them at about 0.2c/20A
Great explanation, thanks 😁👍
No problem 👍
Hi Andy. I am following your channel and it became my inspiration and guideline when I made my both 48V solar hybrid systems based on 280Ah cells. I am continuously upgrading both the system in the house and the second property. Whenever I watch your films I see that red lawn mover on the side and somehow expect, what is logical for me, that you once electrify it and take out the gasoline engine out of it. Well i know you do not announce such things in advance, but if possible give me a hint if i should wait and follow what you did, or do it myself first. My intention is to use 16 pc 280 cells as what we have in our solar systems, though they are heavy, but it doesn't matter for flat surfaces you and me have. As sun/rain protection also a bigger panel would be good and then park the vehicle outside to charge, when there is sun. I am not an engineer and am unsure which rpm and power of 48v DC motor to use. That is my biggest and only concern. My second property with equal solar system is my campsite with 8000sqm of grass, and your property is not small either. I spend at least 6 to 7 liters gasoline every week in the grass cutting season plus noise and maintenance . My properties are in Serbia with plenty of sun in summertime. Give me you thoughts on this when you catch time or at least inform if you have such project in mind? I wish you all success and can only admire your work, enthusiasm and engagement. Hobbies like what most people call what you do are mild expression for what stands behind all that, and I have experienced at least a part of that, so i know how much you work? Kind regards, Vladimir
Compression not much discussed that I can find, thanks!
Very Great Point ! Thank you ! I have 48v bank 15 PCS 3.2v 280AH Daily 15s 120AH BMS & a 48v LTO 2.3v 40AH 20 PCS !
Why did you go with a 15s battery and not 16s? Ah, you have the LTOs in parallel...
Gawd DAMN. And here I've been putting off these batteries while I try to research how I'll compress them. I do think I'd rather use cables than bus bars out of fear of the terminal/post stress during expansion and contraction
Well said. thanks for sharing
thanks Andy that's very helpful
Thank you.
100% correct Andy, Nowhere in the Eve spec sheet does it mention compression. Fixture and clamp yes, to keep the bloody things still as vibration will stress the terminals. I can't see sunny Queensland shaking to much in the near future unless Andy drops another bombshell that he is going................on holiday!!!!!!
Uhm, oh, ah, I have a few days off after Easter, so actually... 😏
I was going to use this time to put the batteries in the shelf though.... if that is what you want? 😁
It mentions 300kgf applied in a fixture. That counts as compression, even if the name is not 100% on point.
@@upnorthandpersonal A fixture is to hold it stationary. They do not say anything about compression or where to compress. It is surmised to apply pressure on the large flat areas but what about the other sides and top and bottom. I have checked the Chinese characters for these words and are completely different shapes so there could not have been interpreted wrong. Until Eve explain exactly what they want it will be up for debate for years.
@@glencooke494 This has been discussed with the actual EVE battery engineers. A 300kgf is applied with a fixture.
Manufacturer is testing at 1.0CA cell current rate. These thick electrode cells should not be subjected to more than 0.5CA for more than short sporadic periods. Cell internal heating will be about 35 watts at 1.0CA current for 280 AH cell. It will get quite warm if 1CA for significant time which is damaging to battery. As battery ages its internal resistance rises which causes more internal heating at high cell current. Internal heating drops to about 10 watts at 0.5CA. Also not mentioned is manufacturer compression fixture also provides some heat dissipation for cell (note the 25 deg C at end of spec paragraph). Packing a bunch of prismatic cells side by side in a tight bundle reduces ability of cells to dissipate heat.
Besides heating damaging electrolyte, it causes more electrode to copper foil and aluminum foil thermal stress that can cause electrode material to foil delamination. Compression does help reduce delamination but only when cell is subjected to high cell current causing temp stresses.
Not knowing what you are doing with compression can cause more damage to cell. It can punch through separator shorting out cell and crack electrode material causing it to be electrically isolated and inert to cell operation. Non-compliant compression can cause mechanical pressure to skyrocket to cell damaging level when cell is fully charged.
Thanks for your insight and additional information. Very helpful.
New datasheet does call for 0.5C for the cycle life.
I love your videos Andy. Compression, another thing to not worry about! I like that. I'm debating where to put my Growatt 3000ES and a 1.5kW battery bank. Do I put them in a basement workshop where it is dusty but steady temps of about 65F. Or should I make my life easier and stick them in a mudroom closet that is very "dust free" but the temp in the winter may approach freezing. I know I can insulate and provide a bit of warmth for the system during the 60 or 70 days when freezing may be an issue. I just don't want to further complicate things.
Die Webung hat hier Überhand genommen !
Kündige mein Abo !
You're probably right, but I like the form factor when compressing these batteriers with some threaded rods and a couple of plywood sheets. It's a practical package.
Awesome video
I acknowledge everything in this excellent video but …… I am about to build a pack to put in my motorhome and realise that compression will be needed to restrain them from movement during travel which would stress the terminals. Perhaps I need to come up with constraint that will leaves a small (say 3mm) gap between each cell. Cheers from New Zealand.and thank you for the video.
Ótimo vídeo 👏, Portugal
Sometimes we over think and quit enjoying our projects/ hobbies.
10 years is a long time .
or 337 years is even longer 😂
I know you like to teach others about this and I like it too, great things will come from batteries
Totally agree 💯%, Ben Z.A.
Only few words on the current subject of cycling, coompressing, etc. When I made and started using my first 16 cells of 280Ah, i realized that if i want to feel comfortable in loading, that not enough. Then I added the next 16 x 280Ah and first today when I have the THIRD set, i see that it is the right thing. Before i connected my third set, i calculated the average per year cycling with 1st set and it was about 160, then with second i unfortunately lost data on bms so i am not sure about it, but now with third set it will be very low. Batteries not compressed, just thick paper between them, maybe 1mm space. Batteries are in the cellar with summer temperatures not exceeding 25C even when outside 37C, and winter time never under 16C. Another benefit is that i had no problem when adding more panels and i am never more afraid to have to much amps when charging in full sunshine. My hybrid inverters (2 times 5kw in paralel) could not cover the additional panels that i added later (now the total of 13,8kw) so i do it with help of Epever 10420AN and the batteries now charge with smaller current than it was before with 16cells and 10kw panels. So adding batteries, although very costly, gives u number of other benefits. I completely agree with you about cycling and compressing approach.
041322/0400h PST🇺🇸 041322/2100h Brisbane 🇦🇺 Thank you thank you thank you to the power of 1 million! I too am a proponent of NO COMPRESSION. The reason ? By the time the Compression technic is applied... The battery chemistry and the battery designs would have become obsolete. I have seen episodes after episodes of several eminent people, enthusiastically exhibiting Compression techniques..... no comments !
I rest my case. My PV system, though quite meager, is running for almost 3.5 years with no compression.
My charing voltage is 14.2V and each cell voltage; at rest is about 3.328v~3.330v, ∆ 0.0003 and battery power 13.31@96%. BMS--JBD. No bulging, no deformation no thermal issues Am I happy 😀or what?
For me; compression is for varicose vein. Danke schoen, herr Andy und 73s...
Thanks Sree. To be clear, I'm not against compression nor do I want to talk people out of it. I'm just sharing my thoughts here and are keen to read your reaction and comments. Maybe I'm totally wrong...
Nabend Andy..
Ja.. Ganz meine Meinung..
Faktoren wie Nutzung Temperatur und der allgemeine Umgang mit der Zelle wird ihr alter aus machen. Ich hab Zellen seit Jahren im Betrieb, welche beim jährlichen Kapazitäts test nicht mal 1 Prozent verloren haben.. Und die stehen wie deine ganz lose im Regal.. Das ist gut so.. Danke für deine Zeit
Thank you
Well reasoned Andy
Thanks Paul.
I have an awesome compression fixture designed, I'm just waiting on some large custom springs to come in the mail. You make a good argument that cooling may be more important. Damn it.
Hi madcow, would you mind sharing what you have cooked up there?
Looking for some designs and examples
@@HG-Pilot In the next few days I'll put together some kind of short write-up with photos and find a reddit forum or something to post it. I haven't started making any of the parts so it would be a good time for constructive criticism. I'm also mostly finished building an LTO battery for my car so I thought I'd share that too in the same place since there are few of those around. I just want to make sure the car doesn't catch on fire before I encourage others to try it. I'll come back here and comment when I have that compression thing up.
Haha. Fantastic. Rock and Roll. Let's squeeze our cells together.
I'd really love to hear more discussion from Andy on this video after his most recent video showing the bloating. I'm a bit concerned about it, which is why I boxed in my cells to prevent them from moving.
Swelling will happen even if you compress. It happens on an atomic level and no force on this planet can prevent it.
i think the only reason to go with compression is if you want to go for the max discharge rate. Some of these cells have a 2 or 3c discharge rate for 15-20 min or something. I can see compression being a bit of help there with the heat making it more funerable to deformation.
Nice video sir 👍
Thank you!
good day sir andy me ask about the position of the battery we have 16pcs lifopo4 battery 48volts what is the best orientation of the battery thanks sir andy
Thumbs up and subscribed!
Hi Andy I compress my cells as they are in a vibration environment on my narrow boat. I do this to stop the busbars loosening the terminals to each cell. Don't know if that is still the recommended way.
OK, that could be another case where it may make sense. Or you could use flexible bus bars to avoid any stress on the terminals. A simple fixture with tape maybe enough for mobile applications.
Hello Andy, my upside down friend.
I was watching some of your old videos and I saw the ones where you successfully put two batteries of significantly different capacities in parallel.
That made me wonder if you could parallel one 24 volt Pack, and two 12 volt packs in series. All different capacities of course. I have packs that I only use seasonally and i wonder if I can use them instead of storing them. Another test?
PS You remind me of a scary shop teacher I had in high school many many years ago.
Best Regards,
Mike Dudley, from up north in Wisconsin
Thanks Mike. Great question. I would not recommend paralleling 2x 12V batteries in series with another 24V battery unless they are all separately monitored. If the 12V batteries have different capacities it should not be done anyway.
You can of course parallel different 24V battery packs with different capacities.
We will do some more testing in this regards, also mixing lead acid, LFP and Li-ion in one battery pack.
Super 👌 thank you
Great show. 🇬🇧🇬🇦🏴
Thanku for this video
QUESTION ON THE LENGTH of the Red and Black. I understand that it needed to be the same. But do u guys calculate the Blue - out of the (-) of the BMS out of - battery? and the black - from the BMS which is like 10 inches in blue and black on the bMS ? my battery got high voltage at cell 15 , 16 but low volt at 1234 little higher than 56789. The 15 n 16 cells got to 3.5-3.67 while other are still in the 3.3. Thanks (i understand from busbar to inverter black and red are the same length.)
I thought that the pressure recommendation from the maker is for one cell only, do you think they put a clamp between a pack of cells and made their electrical performance test ?
I have these exact cells that have been sitting in my garage for 2 weeks while I think through the compression and box design. You’ve convinced me to forgo all that and I’m just going to start using them. Thank you!!
Heck for the cost of a cheap ratchet strap, $3usd and a small piece of scrap 2x6 on each end
Wrong compression can cause damage to the cells. RCin Fla pointed this out in his comment here...
@@OffGridGarageAustralia oh I was still going to do a box and some fixture but I’m not going to worry about compression calculations. I’m actually more concerned about terminal and busbar stress due to expansion so I’ll work towards keeping the cells affixed as best as possible. 👍🏽
I like ur thinking Andy. So to be clear on the reason for compressing, it is to avoid any additional mechanical movement/forces on the busbars while under charge or heavy loads, is this the main point of that theory? Or does it also extend cycle life due to a tighter/ denser mass? People could get real crazy & start creating little cabooses with bearing rollers under individual cells to allow for some movement here. Good info, thanks!
yea ... not a concern for me ...Thanks Andy for proving my point to some people I know 👍
It's like Mercedes or BMW, Ernie and Bert, Al or CU bus bars... you cannot love both 😁