LFP Cell Compression || The What Why How & Very Important Considerations || Step-By Step Tutorial

Full article here: store.currentconnected.com/le...
What is Cell Compression?
Cell compression is quite literally squeezing/fixturing the outer aluminum case of LFP (LiFePO4) cells to prevent delamination of the internal components. Delamination leads to a reduced lifespan of the cells, as well as additional stress on electrical terminals. Internal forces are constantly acting on a thin aluminum case that is not strong enough to resist these forces. Lack of compression leads to damage of the cells, as indicated by swelling and premature battery failure.
Why Is Cell Compression Needed?
With the latest technology of LFP cells, many advances have been made to increase how much energy can be stored in a given volume. Engineers in general regularly face the challenge of fitting “more” into “less”. Sometimes to accomplish such a challenging task, compromises must be made. In this case, to create more space, a thinner, less structurally integral material has been chosen.
The thin aluminum case cannot withstand the internal forces exerted when the cells are charged, but the new design never expected the cells to be used on their own. The greater majority of these LiFePO4 cells on the market today are originally intended for use in Electric Vehicles (EV’s). Automakers and pack manufacturers are already designing the packs with the compression in mind, because the demands of a solidly held pack in an electric vehicle where vibration is guranteed are much more intense than a stationary solar power system. By using a single compression fixture on an entire pack as compared to many thick plastic cases, significant space and weight is saved, leading to higher capacities in the same space.
When Is Cell Compression Needed?
More times than not, cells will require compression. 95% of all aluminum cased LFP cells on the market require compression. While the exact wording varies, most high-quality cell manufactures will make note in their data sheets. Aluminum case batteries that do not require compression do in-fact exist, however they are rare. Asking the vendor you are purchasing the cells from is usually a good idea, however not all vendors are fully educated with regard to the engineering considerations of each and every battery and manufacturer requirements.
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[@Doctorbasss]

VERY VERY VERY IMPORTANT to consider with these new compact LFP cells!!! Isolation between cells!! I have measured 5mA current between the aluminum casing( that is tie to the positive with some resistance) and the negative!! so if you tigh them together and the fragile blue sheet puncture, there is chances that you will have a slow current leak bwteeen two cells and get them out of bvalance pretty quick. Thundersky, CALB or many other plastic casing dont have this problem but aluminum casing DOES!... the blue adhesive sheet around teh cells is not a good protector! any conductive dust or edge damage will expose conductive aluminum. also watch for the bottom there is a black plastic sheet that is not sealing it so any condensation will end out making a conductive path to the aluminum at the bottom and make your battery rack tie to one or more of the cells if it is also made of conductive material.

[@audiophilephile]

Agree fully. I prefer fish paper between the cells. It's pretty much designed for applications such as this.

[@faded.0913]

Just got some catl 280Ah cells and the alu casing has potential like an 18650

[@baylanger]

The isolation between the sheet should be Neoprene or Polyethylene with a Firmness @ 25% Deflection of ~13-14 psi. In the USA Grainger has 3/16" Neoprene and in Canada Polyethylene 1/4". There are articles on the net from manufacturers on this topic. The cells must be able to swell, compressing them and not allowing them to swell slightly isn't much better and the effect is that it impacts expectancy life.

[@Doctorbasss]

Fish paper is a ULTRA BAD material that too many people use, not because it is the good material but simply because it is popular. In fact Fish paper is not Hydrophobic which mean it will trap moisture inside and loose isolation caracteristics. It also acelerate rust on the cell can when ionic path is created from electrolysis and attack the protective nickel on the steel of cell can. Fish paper negativ effect will not be seen duringteh first month bot over the years, killing cells with slow short. @@audiophilephile

[@josepeixoto3384]

@@baylanger they must be allowed to swell?? by how much?? that is a tough one, ...

[@flyingtools]

Good video and explination. Thank you. Im building a 48 v battery from two volkswagen e-up and im using the oem moduls after i change the cell configuration to keep the correct pressure on the cells. And i think, like you that this is very important.

[@gregb1714]

I would setup the final cell configuration with bus bar spacing and then compress only once. You can just jumper the wiring for the top balancing (as long as it doesn't get too hot) since it is not critical and rarely performed.

[@videopipeline6419]

The step that is omitted from this tutorial is: put separator pads in between each cell. "PORON EVExtend Battery Pad Material" is an example of a foam specifically designed for this purpose, but almost any foam or soft rubber with the appropriate compressive strength (~10psi - 12psi is optimal) at the intended compression level (% of original thickness) will work.

[@davidborden3181]

i've seen fr4 fiberglass as another recommended material to put between the cells, but is foam or rubber better in your opinion? My battery will be put into my van and so will have to be able to withstand vibrations. fr4 is rigid so i'm worried my cells will chafe against it.

[@TheNone724]

Hmm I wonder if I could use silicone heating pads between these cells to have isolation and pack heating in cold

[@doppler3237]

that's exactly how I built mine about two years ago, about 14.5 KWH 4S 120 AMP overkill solar all 4 going to common bus and except for a BMS recently dying its been a great system. Running my AC on the RV anytime I need it. The angles are great as lift ledges too.

[@xraykadiddlehopper8067]

Thanks Dexter 👍 Your opinion is valued. Stay safe 😎

[@stephsoltesz6731]

1) Please "sleeve" the threaded rod to prevent ANY contact between cell sides and rod. Plastic/Vinyl tubing or even wire harness tubing. The thin vinyl wrap on the cells will offer no protection from rubbing chafing or such. 2) Alternative to using "Hard Board" plates & rods, 3 strips of Polyester Strapping (1/2"-3/4") as used with heavy shipping packages with or without buckles, works quite well and is commonly used by battery pack assemblers. Recovering "slightly bloated" cells is possible. - Discharge to 2.75-3.00V Temperature at or near 25C/77F. - Do no more than 4 cells at a time, once properly flat, bind the "set" immediately. - LIGHTLY compress (Finger Squeeze tight only not pressured) with 2 Full Plates (1/2 wood etc, on large face), allow 2-4 hrs then squeeze "lightly" and wait another 2-4 hrs, observe carefully NOT to put too much pressure, it is a matter of being "gentle". 2, 3 times should be more than enough. NOTE This is for only Mildly bloated cells, be slow gentle and cautious, do not rush and force anything ! IF it requires more to flatten out, the cells are not mildly bloated. Note regarding the Binding of Cell Groups. It is best to bind them into functional blocks of 4 cells. If for any reason you have to replace a cell or adjust a block of 4, then you only have to rebind that block and not a whole pack. 48V/16S = 4 blocks of 4 cells. Adding a Pull String (heavy duty Nylon) to each bound block can make it much easier to extract from an assembled pack.

[@checkingoutgypsymike2075]

I just watched his older video where he stabbed the battery and asked about pressing slightly bulged batteries lol. My 8 280ah cells came in two packages. One cell in each was slightly bulged where as the rest are sunken in, i asked if they could be pressed back in. The buss bars dont have much room to slide on so they are tight on the two swelled cells, good to know they can be compressed if i ever take them apart and they bulge more. Have you seen a video of the pressing them together? I watched a video of a teardown of smaller cells where two cells about doubled in size when pulled out.

[@stephsoltesz6731]

@@checkingoutgypsymike2075 I followed such a techniques without issue on some used EV Grade LFP I received, took me a few days of gently doing so and it worked ok, trick is GENTLY noo force. BTW: No Aliminum Cased cell is "perfectly & Absolutely" flat, as they are not much thicker than a Pop Can. They can expand and contract by as much as 2mm (safe marging). Beyond the total of 2mm and there are will be other issues and do NOT attempt to reflaten.

[@denniswattenburger1260]

I used PEX tube for my 4 cell battery. I'll be adding center rods making it 6 rods total.

[@joshnabours9102]

Out of curiosity, what is the source for the information you explained in this video? It is always nice to be able to read the technical documentation directly. I find you usually learn even more from that.

[@offgridd]

At what s.o.c. do you apply the compressing voltage? since the thickness varies with the s.o.c, one might consider a spring pushed forcrpe that will keep the tension much more stable during the expanding and shrinking of the cells

[@ricardophelps6323]

Thanks for posting this video. Some people say compression is not required but the CATL 280Ah spec sheet I have clearly states for maximum life >6000 cycles the cells should be compressed with 300 Kgf for at least the first 180 cycles or 6 months. Charging max 0.5C @ 25 C.

[@greatdane3343]

Good video. Thanks for sharing.

[@Tb0n3]

If you had a strapping machine you could use the angle iron as edge protection and pull it together. That way. I would recommend using channel aluminum rather than angle so you reduce the width of the pack and it's still quite strong

[@WG7D]

Nice work! subscribed!

[@powerwall]

Great Video

[@h8GW]

Any reason not to use plywood? I'd imagine it's a good amount stiffer and you might not need the angle iron.

[@powerwall]

What do you think of the bracket format in my profile photo? Looks pretty much similar with your DIY?

[@robbehr8806]

Good video!

[@Zorlig]

Thanks for the part at the end. I used an active balancer to balance in place. Just took a while but worked great.

[@HighTechLab]

Nice work! I just recommended this to a customer of mine that VHB taped their pack together and then had to replace a cell and re-balance things out

[@wobbleszo]

The downside with the balancer and LIFEPO4 is that the voltage curve sits flat for ~75% of the charge, so the balancer will stop when the voltage matches, but thee cells could still have a significant difference in SoC.

[@Zorlig]

@@wobbleszo oh, you just do it while floating at 3.4

[@Dragon-Slay3r]

No problem

[@4evermetalhead79]

Wow. There’s something I actually had no idea of, but i am aware of it now. 🤯 thanks for that. ✌🏼 though what happens if a fully charged cell is removed from compression? Instant bulge or something? 🤔

[@LithiumSolar]

Great video! You did a much better job explaining the need for compression than I had. One thing I noticed though is that you didn't use any separator between the cells. I don't feel the blue heat shrink wrap is sufficient due to the small charge present on the casing. What are your thoughts on this?

[@HighTechLab]

I just got the new 230ah aluminum ones, 30mv difference at 100->0 soc test

[@LithiumSolar]

@@HighTechLab Were yours the same EVE cells I have? I really like mine and have been thinking of ordering 64 more while the price is still good.

[@vinodvinees1629]

. .

[@B4x4]

Quick question. Why do you mix mm and inch on the same template? Why not display bouth everywhere??

[@victorpatras1582]

Hi. My batteries are bulged after two years of use. If I make the compression now will I damage them?

[@gregb1714]

A couple safety concerns: I would add a thin layer of insulation between the cells rather than just trust the thin blue cell plastic. I would also add insulation between the cells and threaded rod rather than just trust the thin blue cell plastic. The cell casings are all at different voltages once the battery is configured and a jolt or bump or vibration could cause the rod to contact the cell cases which results in fireworks.

[@Doctorbasss]

I tested 5mA current leak on the EVE280Ah between the cell aluminum casing and the negative terminal.

[@carrolwright7915]

I agree. I will be doing something simular to what he has done with plywood and threaded rods. But I will put insulators between the cells. And using plastic tubing to cover the threaded rods. No reason to have a short from the cases.

[@rocktech7144]

I have been running those calb 180 cells I bought from you for a year now. I don't even have a BMS attached and they go 20-80 % every day staying within 45mv of each other. I am IMPRESSED with this result so far. The pack is an 8 cell 24 volt configuration.

[@Dragon-Slay3r]

RockTech webbing? How do you like your Tbone

[@realeyesrealizereallies6828]

20 and 80 % is a guess in the dark, but, maybe...

[@julihm]

Hi Your video is very detailed and it is helping me a lot to build my battery my question would be if you can compress the battery cells even if you don't know the SOC (I only know de volt =3.27) Or better discharge them before compressing. (The ideal is to compress them when the SOC is 25-30%)

[@GiaHan.2009]

Thanks you!

[@glisse45]

hello, what tightening cut of the connection screws

[@carlosmf6954]

Thanks

[@danielninedorf5502]

The aluminum case batteries, being the heat source will expand more then the aluminum angle frame or the steel 3/8 rods. There are material specific thermal expansion tables.

[@toobglued]

if a pack is compressed and charged, will it permanantly bloat if compression is released temporarily to service a pack ?

[@LeonGiafaglione]

Thanks for the great video. In your opinion, if I am running an active balancer as well as my daily BMS do I need to top balance my batteries when I get them or can I just let the active balancer do that over a couple of cycles?

[@michaeldoherty2289]

I understand that initial top balancing is extremely important. If its done properly and the cells are the same voltage, the cells ought to stay in balance for a long time, especially if you are using solar and not doing use cycles every day. If you are running active balancers and a quality BMS it should stay in balance. Active balancers are not meant to do the initial balance if the cells are very different but are very effective in keeping initially balanced cells in balance.

[@ynzeselders4184]

why not configure the cells in the right order the first time and just connect them all in parrallel with some thick short cables or the diagonal bus bars while top balancing? that way you only have to compress them once and just change the busbars to the normal ones when balanced. interesting stuff

[@someguyfromafrica5158]

Can a few rounds of gaffer tape replace the plates and screws once compressed?

[@olafschermann1592]

I have read that the compression is only necessary at the very first chrging. This also means that an initial capacity measurement (without compression) at a dealer will permanently loose capacity.

[@josepeixoto3384]

oops... is that so? terrible,because lots do it free air!!

[@aronhorner4611]

The battery cell is under the action of 300kgf force ,the battery cell is under the action of preset 300kgf force, after standard charged and 60mins rest, discharge to 2.5V cutoff with the current of 1.0C(A) at (25±2) ℃, and then start the next cycle, end with the capacity decrease to 80% of the initial capacity. The number of cycles is defined as the cycle life of the battery.

[@halfpastnews4999]

Great Job. Some constructive criticism . The clamp is on the top and bottom edges of the bulge circle you drew out. there should be three rods to even out the compression. Also the metal you used is referred to as "Aluminum Angle" Is it necessary to leave the clamp in place or is it removed after the balance is done?

[@ekkehartmeyer701]

It will be not even so much necessary to clamp them for balancing but for long term the amount of cycles will increase much when they are compressed.

[@GiaHan.2009]

Thanks you too much!

[@luizmattos9031]

I really liked your idea and what you say makes sense. But then, wouldn't it be safer if you put this plate between one battery and another? Another detail is that for battery swelling to occur, it is necessary to don't use excessive voltage above the recommended by the manufacturers and also not to use a BMS to avoid these problems with this swelling and even the preca of the batteries.

[@heardandtested]

I'm really considering using this cells for car audio.

[@esandquistSr]

How many can we safely compress in series? I have a 16S... I was thinking 8 and 8

[@powerwall]

Tested on 100ah, 8pcs will be ok, around 44lbs

[@MR-ub6sq]

- I wouldn't talk about "compression" as the name of the structure you described, but only about preserving the original dimensions. I've noticed that some people think that this kind of threaded rod structure is supposed to PRESS the cells against each other with a certain N force. That is a misconception. the purpose is to make only a structure that WILL RESIST a certain compression directed outward from the cells without letting it change the shape of the cells. If before the cells are put into use, by tightening the threaded rods, inward compression is caused to the cells - it is useless and possibly harmful if it changes the shape of the cells at any point! - I feel that you put the aluminum upper and lower corner pieces too far apart. Now there is a lot of unstabilized space between them for the cutting board to give way to the bulge of the cells. Personally, I would have placed the upper "collar" an inch lower and the lower collar correspondingly an inch higher. If the location of the upper and lower stiffeners were clearly closer to the center of the large side of the cell, it would indeed significantly prevent bulging compared to your current solution. So the cutting boards off and to drill new holes. - Many people who build a battery pack in a similar way also place a sheet of cardboard against the surface of each cell, so that they don't damage each other with a hard surface, with a soft sheet of cardboard protecting between them. - The threaded rod should also be coated with some kind of soft hose to avoid hitting the hard metal and damaging the sides of the cells. It is recommended to place the threaded rods as close as possible to the side of the cells, so that the cells cannot slide sideways under any circumstances.

[@akkoxe]

It is necessary to place an insulator between the cells, and heat-shrink the threads of the studs. Better at three. Because if the thread cuts through the blue shell of the cell, it will be very bad. The same thing will happen if the blue shell deteriorates over time and a short circuit occurs between the housings and the adjacent cell.

Never tighten the fixture to factory specs when the battery is not fully charged to 3.6v per cell.. I would suggest as low as 1 to 2 foot pounds on the nuts at most.. Slowly bring the battery pack to full charge and even back off the pressure a bit as they charge.. Top charging all the cells paralleled at 3.65v before putting them in pack series is old school.. Using a modern BMS with 2 amp active balancer and slowly bring the whole pack to full charge allows the active balancer to do all the work.. Alot less messing around compressing uncompressing connecting then disconnecting and rearranging the cells.. Compression is only good for new virgin cells and is used during the initial 10 to 50 or so cycles of conditioning to assure that any trapped gas bubbles get forced into the internal channels built into the cell laminations.. Once this period is over compression is not really going to improve cell life.. He was correct when he said overtightening can and does destroy the batteries.. If you are going for a long life be aware that these batteries will degrade over the years no matter what and even with gentle care they will be at 80% capacity in around 10 to 15 years when that decline will increase.. A slightly bulged battery is no indication of it being trash.. What trashes these cells is exceeding the charge/discharge rate and voltage minimum and maximum.. Very light compression should be maintained if you plan on going from sub 2.5v to 3.65v per cell on a constant basis but be aware this will quickly degrade the cells.. The best route for long life is never exceed .5c charging or discharging and keep the cell voltage between 2.8v and 3.5v.. This alone will add thousands of cycles to these cells.. It is also always best to have the cells standing terminals up for that initial conditioning number of cycles before you put them on their side..

[@vincentstouter449]

How does compression effect Heat Transfer? What is the cause of the structural instability?

[@Mike-01234]

If you open up UL approved battery storage they don't compress the cells. They do put them in a fixture to keep them from moving.

[@peterking1134]

It’s about time you post something!

[@HighTechLab]

:D You are not wrong, BUT, you are also not right! I've been Mr. Tech Support running our new business, and I've finally gotten to the point where I'm making videos to refer customers to so that the technical support calls are easier.

[@kandkob]

Why not use those longer bus bars to reconfigure to 12v, that way you don't have to disassemble?

[@HighTechLab]

It's a lot of exposed metal and very difficult for any parallel configuration

[@antronx7]

You should have installed 3rd threaded rod pair exactly in the middle between the two rod pairs. That is where most bulging will happen and you don't have that area braced. HDPE is not rigid enough and will flex. Better to use 3/4" aluminum plates. Each battery will also expand by 0.5mm during normal use so you need to allow for 2mm expansion with 4 cells while maintaining 300 kgf pressure level. That has to be done with either spring washers or springs each capable of 75 kgf if 4 rods are used. But ideally you need to place a load cell between battery cells and measure compression force as batteries are cycled.

[@LawAbidingCitizen117]

Wow that's really a lot of work to get the max life out of the cells...

[@Dragon-Slay3r]

Webbing is going back like 20 years ago 🤣

[@wenhaowong5549]

hmmm, i charge some different cell to full SOC, but they didn't go fat, i think maybe the current is the crucial key? I observe that if you charge and discharge with low current something like 0.2c or lower, it will not swelling (overcharge or over discharge is different matter).

[@sreekumarUSA]

080521/0831h PST 🇺🇸 Thank you Wen. You are right. Bulging is caused by gassing internally. The cause for bulging, is due to excessive Current/ voltage being supplied to the Cell. I concur to your wise statement. There are hundreds of LiFePo4 battery manufacturers in the world and none of them have “compressed” their Prismatic cells inside the containers. Did it cause any issue after charging and discharging the battery at the at the PRESCRIBED current and voltage? None have been reported. NO NEED TO FIT ANY CONTRAPTIONS TO THE CELLS. It looks ugly and uncalled for.

[@HighTechLab]

I hooked up a single 310ah cell and charged it at 10a rate, when the cell was around 3.4v, the cell grew around 4mm in size. After immediately discharging the cell, the damage was done, and the bus bars for the cell no longer reached to a cell next to it. As I said in the video, some cells do require it, others may not. 90% of the commodity grade cells on the market do require it, however cells like the Fortune cells do not. At the end of the day, compression is not going to hurt anything, the worst that it can do is nothing. It is also a good idea to keep the cells held together so that the terminals don't experience fatigue.

[@LithiumSolar]

@@sreekumarUSA I do agree to an extent. Bulging is definitely caused by excessive charging/discharging and overcharging. However, it is not the only cause. I've charged cells individually at a low rate without damage as well. However, at least for the cells I have, the specification sheet from the manufacturer indicates you'll see an additional 1000 cycles, before 80% state of health, if compressed. That's HUGE to me and well-worth compressing even if I tend to agree that it's typically (but not always) caused by abuse of the cell. 1000 more cycles calculates out to almost 3 years if cycling daily!

[@PavolFilek]

Beautiful video, for how long you can stop chain reaction from one cell to another. LFP produces flammable gases. H2, C2H2, C2H4, CH4, C2H6 etc. After ignition your house is gone like cardhouse. A lot of videos of YT that LFP are more dangerous like NCA or NMC.

[@HighTechLab]

@@PavolFilek lfp is an order of magnitude safer than nmc and nca, what are you talking about

[@PavolFilek]

@@HighTechLab NO, a lot of houses destroyed in EU. From LFP after inignition.

[@pashko90]

8 and 13/16s. How nice is it to use a metric...

[@j.badinter988]

"angle iron", 'angle iron-aluminum"...! You need a protection layer between cells and a plastic tubing around your 3/8 or 1/2 inch threaded compression bars to avoid the three touching the cells.

[@tomlibero3780]

Hi! How to wire 32 pcs. LiFePo4 into 48v battery bank? Thx

[@repairman2be250]

One bank of 16 cells and another bank of 16 cells. Then you can have the two banks in parallel.

[@marktheunitedstatescitezen185]

And I’ve seen put over the threaded part of the next to the batteries rubber fuel line not to scrap the cases !

[@troyyarbrough]

Just because cells are slightly bulged out does not make them junk. If they still take and hold a charge and can be discharged they still have use. Will Prowse took a bunch of grade b, swollen cells and connected them together with longer buss bars and has them sitting on a shelf. He uses them daily to charge his EV.

[@ernieschatz3783]

I was about to say that. More people than just Will P. have reported good performance from swollen batteries. I suspect overall cycle life will shorten but put the batteties to use if they are performing well.

[@mihaitaiosub]

Hello,thank you for the video.I received 32 CATL 302 amp cells a week ago and they were all very little swollen. I wrote this to the company where I bought them from, and they replied that the CATL cells are always slightly swollen.Company is called Shenzen Basen, I think it's reliable because I've seen a lot of good reviews about them. What do you think, have I been fooled and the cells are not new, or are they right?

[@JPHER217]

Naah i think you are good just measure The ir, do The standard testings. Also i would recommend you go watch off grid garage on youTube, The dude have some intresting videos on comoression or not to compress.

[@mihaitaiosub]

@@JPHER217 Thank you,i allready watching those videos.

[@sreekumarUSA]

080521/0848h PST 🇺🇸 MIHAITA, thank you. You are right. I also have Shenzhen Basen 3.65V (max) @270A Grade A Prismatic cells X 8. I didn’t “compress” them at all. They are running well into 2 years without “bulging” I have heard several unreliable comments before too. Take care and be safe.

[@mihaitaiosub]

@@sreekumarUSA So,what do you think, have I been fooled and the cells are not new, or are they right?

[@drbytes68]

@@mihaitaiosub : they are used cells. Otherwise they'd be flat as can be

[@offgridwanabe]

Always nice to prolong life especially for the large investment of lithium batteries.

[@Jack-le7vk]

Not really. A 280ah pack is ~US$400, so $/ah they are extremely well priced.

[@offgridwanabe]

@@Jack-le7vk ya everyone uses that argument but it is still a huge outlay of cash to build a 48 volt power wall of any size to run a home. Also in Canada they are a lot more money.

[@LithiumSolar]

@@Jack-le7vk you're pricing is based on 4 batteries. Some people have 32, 64, or hundreds of them. So it's a large investment ;)

[@rebar-king]

One argument I’ve read is that battery technology will change significantly within the average charge cycles that compressing them for an added 1000 cycles is a moot point?

[@igorkvachun3572]

Yes Akb LiFePo4 🔋 ⚡ 👍

[@rilosvideos877]

Some say there is a 30x Ah-series that typically needs to bulge a little bit wihtout loosing any capacity. There's a natural movement inside the cell as the chemitry needs some 'air to breathe'. I am not sure if this holds 100% true scientifically, just saying...

[@shinosg-wiz4619]

I charged those cells to 4.2 for like a min and didn't swell. repeatedly charged to 3.65 and no swelling. Used blue cells for 3yrs now and no swelling whatsoever and didn't compressed them. Am I lucky or there's something I'm missing?

[@boundary1918]

if you do not charge with 1C current this is not necessary

[@pd4689]

Why are you even creating custom cross connect bus bars? Feels like an OCD issue to me because you want all the + posts to point north. And your compression is weak, look at the plastic bend when you compress and it bends in all the wrong places. Use 5mm steel plate at each end, use 2x2x1/4 angle iron, and better still, compress using engine valve springs. I hate to say this, but this really doesn't cut the mustard when it comes to cell compression, it feels a bit like lip service to tick a box.

[@easylooker]

Is top balancing even necessary when your not going to charge above 85%

[@parkerbirch1475]

Sounds right I would go for it.

[@brianvandy4002]

Please note, that the cycle life of these batteries is without compression. Don't think that if there is some swelling that the batteries are automatically "Junk." The spec sheets indicate that if you do compress the batteries it will extend the life past the specified cycle life.

[@Henning_Rech]

Just read the datasheet. Cycle life is indicated WITH compression (300 kgf = 3000 N - you see it even here in the video at 2:27 )

[@brianvandy4002]

@@Henning_Rech I'm saying that if the batteries swell they aren't automatically bad. It just means their life is reduced slightly. Also, swelling can be bad for the connections if using bus bars that are JUST long enough to go from post to post, so if you aren't compressing you should use cables instead of bus bars.

[@pgScorpio]

Compression has NO influence on the cycle life at all! Compression only has effect on initial capacity, if applied during the first 1 to 3 cycles. After three cycles compression has no effect at all! Compression does NOT prevent swelling, as swelling is part of the normal degradation. Compression just may cause the safety vents to vent earlier...

[@DanBurgaud]

9:08 12psi is the optimum. therefore, you ought to provide something between 6 and 12psi.

[@marinetrax]

I have 16 304 Eve batteries, two rows side by side, (48v 16s block) with two rods running down the side. Do you tighten up these four rods to 12psi? Thanks

[@haroldmcdermott515]

Top balance is not really necessary balance maybe necessary what I mean is just make sure there all the same voltage by Connecting them all in parallel and letting them set for a few hours so you don't need compression to do that, then charge to full and check with a multimeter to make sure there the same if you have adjustable power supply you can Simply put a little bit of energy in the one low cell, but the bms should do the same thing.

[@codyfisher7798]

You have to have clamp pressure in the middle of the cells as this is where they bulge from the most. You should have one more set right across the middle and it’s a must for safety to add insulation between the cells. Several things wrong with this setup.

[@honumoorea873]

Not good, sheets got to be put between each cells and rod got to be insulated too.

[@stanlibuda5786]

The cells only begin to expand when the charge exceeds 3.4V. Until then, they do not have to be pressed. But I still compress my cells anyway. Just in case. ;-)

[@bwilson948]

Thermal Conductivity: Aluminum boasts exceptional thermal conductivity, allowing for efficient heat dissipation. In the context of lithium-ion batteries, which can generate heat during charging and discharging cycles, this property is crucial. It helps dissipate heat away from the batteries, maintaining optimal operating temperatures and extending their lifespan.Locking down cells due to a bad choice in a bus bar is just moving one risk to another.

[@realeyesrealizereallies6828]

Personally, I wonder if charging to 3.40 volts a cell, and reducing the amps as you get closer to that number, with spaces between the cells and some computer fans blowing away the heat is a better idea..Take away the conditions that lead to bloated cells in the first place, having an over sized system(battery capacity), will do alot of that..Being gentle on your bank with low C. charging and discharging rates, more voltage less amps...If you have a big enough bank and your charging with solar and you stay within 40 to 80%..Those cells will last forever..Get a JK BMS and set balancing for 3.40 when the cells turn off, and balance every 3 months or so, the more you stay away from fully charged and fully discharged, the better off your battery will be..Heat kills LIFEP04 batteries and electronics...When EVE did those experiments they were cycling those batteries hard, full charge full discharge, don't do that...

[@easylooker]

I used 2x10s. It's pretty stout

[@mohamedalmuhairi324]

1:00 no you don't you think you need to do that but you don't

[@NikolaySemenkov]

About that 300 kg force of compression per cell. So for 4 cells it would be 1.2 tons. How to make sure it is that high? If you know the threads count on the rode, you can set the torque on the wrench. for 4 bolts would be 300 kg force per bolt for those 4 cells. See Bolt Torque Calculator. I just used one. Result is: M6 rod is too thin and will not sustain that load. M8 seems work as following: Application Data Major Bolt Diameter: 8.00 mm Bolt: Pitch: 1.25 Bolt Proof Strength:303 MPa Recepticle Length:12 mm Recepticle Strength:1450 MPa Applied Tensile Load: 300 kg k Factor:0.2 Recommended Torque 7.413 N-m (0.75639 kg-m) (5.467 ft-lb) What torque did you put?

[@dmitryvodolazsky]

*>for 4 cells it would be 1.2 tons* No. 300kgf*4 is summary force for parallel assembly = 1 layer with 4 cells. But here is sequential loading, each layer compressed by same common force.

[@SnowyOwlPrepper]

300kgf would equate to a 661 pound weight (a little bigger than one cubic foot of steel 490 pounds). With 71 square inches surface area that calculates to 9 pounds per square inch for your battery cells. The rods and angle iron concentrate the force to a narrow strip. That strip is an area that is only made a little wider by the Poly panel. Differential forces have not been studied for these batteries. So no real extrapolation of life cycles should be made. An alternative design to distribute force would be to use "equalizers" across the face. (search on fixture to distribute force). It would not be two hard to set up a pressure transducer to monitor the quantity of force in any setup including the all thread/angle setup. Another alternative is to use a fluid/gas under pressure. A bladder or a piston/gland setup could be easily made. Then a pressure gage would work. If my cells ever arrive, I will try to show an example. Has any one set up a chamber that could be pressurized to the 10 psi? That would apply force uniformly over the entire cell.

[@bradley3549]

I have had similar thoughts regarding a load cell transducer. The bladder idea I think is not appropriate however. My understanding is that you want to restrict movement of the cell guts. A bladder may be able to provide *pressure*, but not *structure*. The best case is simply a sufficiently rigid endplate. I agree a cutting board does not meet that requirement. As far as uniformity, using a torque wrench should be more than sufficient assuming that rigid end plate. It would be able to provide pretty repeatable and even clamping force. I did the math a while back and it was a surprisingly low torque value on a 1/4" allthread fastener. Something like 30 inch/lbs to provide roughly 600 pound/force, from memory.

[@SnowyOwlPrepper]

@@bradley3549 Very good thinking. The structure is important in matching the geometry of bulge. I was pondering using a bladder that is commercially sold to locksmiths. The first problem was they are only rated to 300 pounds force. Secondly they are not ideal for using in extended periods of time. Apparently the bulge is more or less symmetrical as one would expect from a rectangular surface fixed at the edges. The bladder, I thought would be a good counter force in geometric terms. With this idea of a good fit, I am now looking at other load distribution systems. Fortunately there is a wealth of Jig & Fixture documents. I am looking at honeycomb aluminum and ridged materials like a product called CoosaComposites. I appreciate the response and thanks for the thread pressure calculation.

[@bradley3549]

@@SnowyOwlPrepper I still think you are missing a critical point. You don't want the bulge at all. The prismatic cells are built flat, with a jelly roll inside. You want the plates to constrain movement of that assembly, as manufactured. The bulging is part of if not the whole issue because it creates asymmetrical stress on the layers within the battery. That said, an interesting problem occurs when you start out with already bulged cells. Are you better to compress them flat, apply pressure but leave them bulged or just let it ride wthout compression because the damage has already been done? I'm heavily leaning towards the last option, but I've not seen any data one way or another.

[@SnowyOwlPrepper]

@@bradley3549 here are my thoughts. The people creating these cells are manufacturing and machine tool centric. Thee term fixture is a machine operators term. Jigs and fixtures are two main devices to hold parts. They function to support and hold in position raw material or part. Clamps and vises are special cases of fixtures. In general a jig holds the material and the jig is moved towards the tool. A fixture hold the part while the tool is moved agains the part. My interpretation of the "fixture" is not a clamp or vise. Both of these are not intended or ideal for a fixture whose purpose is to keep the part from moving. Thinking of the cell as the part that is applying a force against a fixture I assume is what the manufacture is talking abut. The tool causing the force on the part is the expanding volume inside the cell. That volume of expansion caused by electrochemical reactions related to the amount of current passing through the cell. Therefore the the fixture should not be designed as a clamp or vise compressing the cell. The cell's internal expansion, which take on the shape of a dome on the larger surfaces of the cell, exert up to 300kgf. The simplest design would be two fixed panels that would not yield below 300kgf. This would hold in a fixed position the material inside the cell. A designer of fixtures would create a system of components that would economically accomplish this task of not allowing the movement. Other considerations would come into play such as heat, weight, and construction ease. I have no clue on the trying to reverse volume by compression. It seems contra intuitive to introduce strain. In that case one would maybe redesign a fixture to fit the dome and not allow further movement. my thoughts anyway. I am looking at chloroplast or twin wall polycarbonate to separate my cells. The fixture will likely be plate aluminum or steel. Cheers.

[@coffeeisthepathtovictory1290]

5:51 Whoa........

[@alanday5255]

In the OLD DAYS we had LEAD BATTERIES>

[@HighTechLab]

And they sucked then and they still suck now!

[@alanday5255]

@@HighTechLab Well yeah in hind site but there was nothing else. You have the benefit of living now not then, but perspective is a powerful tool.

[@rOSScOGITANS]

never seen battery compression in professional battery packaging , pylontec and other company battery are just inserted without particular compression, I think that any swelling of the batteries is due to errors in their management, in particular to too aggressive charging values ​​that can alter their internal chemistry

[@EddieSpaghettiYouTube]

Not true

[@orrinkelso9295]

Doesn't look like iron to me.

[@HighTechLab]

Depends on where you're looking. You'd have to open it up to see the Ferro phosphate material

[@shelekhov]

those inches are so convenient to use. 8 145/9284 instead of 286mm :))))))

[@surfreadjumpsleep]

all of that throwing around bus bars and talking at the same time... all while not wearing protective eyewear made me cringe!

[@TheAnthonyBrandi]

you went way to tight

[@mwint1982]

Compression is totally optional. It adds to the life, but that's all

[@HighTechLab]

It totally depends on the battery cell and manufacturer, just like I said in the video. I've hooked up a single 310ah cell and charged it at 10a rate, when the cell was reaching around 3.4v, the cell had already grew around 4mm in size. After immediately discharging the cell, the damage was done, and the bus bars for the cell no longer reached to a cell next to it. Meanwhile, the 170ah cells I've shown elsewhere on the channel, assembling with VHB tape, have no such issues, and compression totally does not matter.

[@mwint1982]

@@HighTechLab thank you for clarifying. It definitely doesnt hurt when done properly. Get a few 1000 more cycles I bet.

[@davidkettell5726]

The cells in real batteries are not compressed like this. you will do more harm than good.

[@kkostadinof]

Incorrect. In "real batteries" they don't care about maximum longevity of the cells. They will last the 2000 cycles while under warranty but not 6000+ that will be their "real" lifespan if they are compressed from the beginning.

[@tlmckee2002]

you basically did nothing in 15 minutes - lol