EVE-280 cells should these be clamped tight or spaced for expansion?

[Frank in Thailand]

For the sake of your argument..
3500ah..
That is 11.5 X 300Ah. Cell sets of 16 cells with 300Ah.

Tier 3 is only 11kw.
My current setup with 16.5kw would be able to handle this, with 1000ah battery.
1000 X 51.2 = 51kw.
16.5kw is just C 0.25 or discharge the +1000ah battery at 75A.

So your worse case scenario is 75 A on the 300Ah pack...
If you would have 3.5..

You have 3500ah..
So you have 7.5A load during your worse case scenario.

Edit:
Unless you are planning to charge the Tesla 50kwh battery (for model 3) with your home built 300ahx51.2v = 15kwh at maximal capacity....

Again... This is solar forum for normal home usage.
Draining the cells as fast as possible to recharge your EV...
Isn't normal home usage

 

[Itohmamma]

Well for the sake of argument, let us say that you have 3500 amp hours at 48 V where you want to charge up a tesla on tier 3, and that’s going to run for an hour maybe more, and all the while he’s certainly like to continue to run all of your appliances, and your two air conditioners in your computer and your large screen TV etc. etc.. I’m planning for the worst case scenario and I realize that when bus bars heat up so do the batteries and the batteries heat up, degradation sets in.
Unless you can predict 15 years into the future? It’s for that particular reason that I am now upgrading my two 48v/250 amp hour 16s Daly to two 48v/300ah daly. As gasoline and natural gas prices increase… the need for renewable self producing electricity becomes more desirable, and maybe absolutely necessary.

Oh yeah by the way, putting the pads between each separate the cells will make the compression quite easy to calculate. Squeeze the 50% SOC pack to approximately 3.2mm , plus or minus. This provides approx 7psi evenly between the cells. Now wherever the weakest point (generally center of the cell) will bulge (up to 1mm when 100% SOC) these silicone neoprene will allow resistance to not exceed 17 psi, yeah let’s point out what batteries can sustain internal damage.

 

[Itohmamma]

@Itohmamma ,
I'm happy for you that you found a use for your liquid silicone pads.
Spacing cells 4.5mm by something semi solid isn't going to do much good.

Not for temperature, not for compression.

What works for you, work for you in your situation.
There isn't a LiFePO4 manufacturer that uses 4.5mm thick gelpads between the cells.

There are more videos on YouTube how professional builders build
.
Laser welding, aluminium busbars and housing under compression.

That's how it is intended to be used.
Not drilling a hole in the terminal, tapping thread..... And so on.

Sure, you can use your angle grinder to make a mixer.

It's also electro motor, have on/off switch, same wattage...
Just don't expect it to be as good as a mixer build by a factory, as mixer from the start...

We are NEVER going to have the same quality and stability a "pre-build" laser welded LiFePO4 battery.

Just only that we have inferior contact with the terminals is already a start.


The 300A example one post earlier...

Drilling holes and tapping threads was something "we" could get away with when the capacity was 20-50ah.
No one was even thinking about giving it "full load" of 50A, mainly because the chemistry wasn't capable yet, also...
The contact... It could not handle that much amperage.


Then things evolved..
50 to 100, to 200 and even 300A.
C rating went up, even to 2..

Only a fool would think that what you could get away with at low capacity, 50A, works the same at 300 or 600A!

The terminal surface did not increase.
50Ah, 150, 280, same terminal size.

When used as we do (not think we want or mightike to do), solar installation.

Charge during daytime, 8-12 hours.
We don't like empty, so we charge probably less then 75%.
In 8-12 hours.

Use at night, 12-16 hours...
C rating of 0.2 we probably never reach.

We can theorise all we want about how the cells would react with "high temperature" due long loads of C1 or C2 (+250A)..
Realistic... We won't use.
If ever... A spike for a short time.

14.5kw solar in Thailand, +1000Ah LiFePO4 and 16.5kw inverter..
Max...
My usual consumption with 2 airconditioning units, 950w mining rig, 2000 watt 50m pump, 1100 watt Reverse osmosis several other pumps (350-500w)...
Even with all 5 airconditioning working, the main pumps starting, I don't come close to the 16.5kw.
Usually it stays (far) under 5000w.

And I'm energy hungry

Electrical cars... That's a whole different ballpark.
DIY Solar forum does not cover this.

DYISOLAR on YouTube does cover EV charge. I’m paying $6/gal gasoline… might be $10 very soon, and for the Foreseeable future. I would rather have more than I need than need more than I have. Besides, larger busbars have less resistance, therefore less heat.

 

[Frank in Thailand]

yeah let’s point out what batteries can sustain internal damage.

That's an easy one.
Not any battery can sustain internal damage

I'm happy for you that you are in the position to educate BYD, EVE, Lishen, CALB on how they need to produce their batteries for EV's.
Please post your scientific study papers, how they are doing it wrong all those years.
Wrong is a too strong word, "have room for significant improvement" is better suited.

I don't hold all the knowledge. You might be right.

Cost efficiency is an important factor for many companies.
It might improve over the "normal" method, increase a few cycle.
usually the busses and trucks get new packs after 3000-3500 cycles.
2% increase in cost should give 10% more cycles. (for factory products)
in 15 years, my inverters probably will have been replaced, and i have slowly build enough "Edison batteries".
They last over 60 years.
with a daily cycle, theirself discharge isn't that important.
I have enough space for huge batteries, and enough space to add a few more solar panels to compensate for the lesser efficiency of the Edison.
@ $110 for 345w, when the nickel price drop again, (5 years?) time enough to start building them (or perhaps buy)

I expect my lifepo4 to last 10 years, before I need to make adjustments to our energy consumption,
up to 15 before they don't provide enough.
my solar panels 20 years, I hope 30, or longer...
the mining rig won't last 10 years perhaps 1 or 2 years.... then 950 watt extra space (roughly 12.5 kw battery)

Before building, I did like most, make many calculations, theorising on what is best, and can it be improved.
yes, cooling solar panel with water will improve output. not practical.
yes, mirrors will increase solar output, but the heat shorten it lifespan..
combination would be amazing...
or just buy 10% more panels, and have stable, maintenance free solution.

Same goes for the battery......
You can try to outsmart the professionals, and might succeed for your setup.
following the "known path" will most likely provide you with a longer term working stable solution.
end of the line provide more cheaper solution, as we do not need to reinvent the wheel.

Reinventing is a whole lot more fun
usually does cost more and doesn't reach the same quality, absolutely more fun

 

[Frank in Thailand]

DYISOLAR on YouTube does cover EV charge. I’m paying $6/gal gasoline… might be $10 very soon, and for the Foreseeable future. I would rather have more than I need than need more than I have. Besides, larger busbars have less resistance, therefore less heat.

Thailand 40 thb per liter € 1.10
europe price as high as € 3 per liter.
3.785.. so € 11.355 or $12.- per gallon in Europe...
those prices are already there.

good thing tesla's are cheap
petrol car €20.000, Tesla €50.000
€ 30.000 difference, : 11.35 = 2650 gallon
petrol car average 25.4 miles per gallon, roughly 105k miles
average 13.500 miles per year (usa)
roughly 8 years worth of petrol costs.
you need to loan 30.000 more at 6.5%
or have 30.000 less to invest with average 10% return..

yes, in +10 years you have reached the ROI (average numbers)

While that isn't that much different from Solar, that one will last +25 years.
i doubt the tesla will last 25 years.
would be great if it did.

I absolutely would like to drive EV or Hybrid
That i have china inverter and EVE cells already shows that my budget isn't capable of buying it.
we drive china pickup on LPG $1.47 per gallon, and can drive way over the 25.4 miles..

Living off grid, where cable to hour home would costs about $50.000 ...
solar is the best way to go.

not due the price of electricity. that's a nice bolus we don't need to pay for that.
only 11 kw.... (tier3) isn't that special. my setup can handle at this moment.
I do have over 11 kw solar production, charging one battery from the other via inverter is kinda inefficient...

my 5.5kw inverter have max 5.5 MPPT.
I have higher voltage setup (+350v) 2 of the 3 inverters are mostly used as MPPT.
they can be used... and a victron solar charge controller is the same price as my 5.5 kw unit.
yes, probably will last longer...
in 10 years, i will see what the development have brought.
perhaps lower EV prices.

 

[Itohmamma]

That's an easy one.
Not any battery can sustain internal damage

I'm happy for you that you are in the position to educate BYD, EVE, Lishen, CALB on how they need to produce their batteries for EV's.
Please post your scientific study papers, how they are doing it wrong all those years.
Wrong is a too strong word, "have room for significant improvement" is better suited.

I don't hold all the knowledge. You might be right.

Cost efficiency is an important factor for many companies.
It might improve over the "normal" method, increase a few cycle.
usually the busses and trucks get new packs after 3000-3500 cycles.
2% increase in cost should give 10% more cycles. (for factory products)
in 15 years, my inverters probably will have been replaced, and i have slowly build enough "Edison batteries".
They last over 60 years.
with a daily cycle, theirself discharge isn't that important.
I have enough space for huge batteries, and enough space to add a few more solar panels to compensate for the lesser efficiency of the Edison.
@ $110 for 345w, when the nickel price drop again, (5 years?) time enough to start building them (or perhaps buy)

I expect my lifepo4 to last 10 years, before I need to make adjustments to our energy consumption,
up to 15 before they don't provide enough.
my solar panels 20 years, I hope 30, or longer...
the mining rig won't last 10 years perhaps 1 or 2 years.... then 950 watt extra space (roughly 12.5 kw battery)

Before building, I did like most, make many calculations, theorising on what is best, and can it be improved.
yes, cooling solar panel with water will improve output. not practical.
yes, mirrors will increase solar output, but the heat shorten it lifespan..
combination would be amazing...
or just buy 10% more panels, and have stable, maintenance free solution.

Same goes for the battery......
You can try to outsmart the professionals, and might succeed for your setup.
following the "known path" will most likely provide you with a longer term working stable solution.
end of the line provide more cheaper solution, as we do not need to reinvent the wheel.

Reinventing is a whole lot more fun
usually does cost more and doesn't reach the same quality, absolutely more fun

Thank you for your support ?. I’m following manufacture data regarding prismatic cell compression increases cycle life. I’m following manufacture testing data on liquid silicone foam spacers. (Which will at minimum reduce heat transfer between cells and contact damage in my mobile application). So at the very least it will help and protect from vibration damage and heat dissipation. 32 LiFeP04 cells is a huge investment, and any thing that helps is worth the small effort.?‍

 

[Deleted member 9967]

Thank you for your support ?. I’m following manufacture data regarding prismatic cell compression increases cycle life. I’m following manufacture testing data on liquid silicone foam spacers. (Which will at minimum reduce heat transfer between cells and contact damage in my mobile application). So at the very least it will help and protect from vibration damage and heat dissipation. 32 LiFeP04 cells is a huge investment, and any thing that helps is worth the small effort.?‍

Ok please teach me.
What the heck are "liquid silicone foam spacers"?
They sound like something I could use as mine are on a moving vehicle.
Thanks you.

 

[Frank in Thailand]

Yes..
I know it's a huge investment.
I did 48x 152 at the price 280 is now, and few months later 32 X 280ah...

I tried to reinvent also..
And being "new" development (larger capacity being affordable) not much was known in DIY world (end 2019, begin 2020)
What a leap has been made in those 2 years

If the pre-build laser welded BYD cells where (affordable) available back then, I best could have bought those. (In Thailand $1250 for S16, 260 Ah) (2xS8)

I lost thousands of dollars due many smaller mistakes, what eventually ended in catastrophe...
Not really, the room was "fire proofed"..
House still there

Keep it as simple as possible, least points of failure and do follow the "known paths"...
That will provide the lost stable setup what will last the longest.

Aim for 10 years...
That is a really long time..
You remember your life 10 years ago? How different from now?
Probably in 10 years the same...

Here (hot Thailand) lead acid dies (unless Air-conditioning cooled) in 2-3 years. We have regular +40c (over 105F)
lead acid doesn't like that

For you, i read Mobile solution.
Unless it's off the road truck, it doesn't have much to suffer.

Your busbars are probably with a stud and a nut..
That is more sensitive to vibration.
Usually I would suggest loctite.
It does make maintenance almost impossible...
Nylon lock nuts?

Please do use loctite if the studs aren't laser welded in the terminals.

Do use quality di-electric grease (oxiguard) and a torque meter (!!!)
It will help so much with the maximum torque the thread (in the aluminium terminal) can handle.
With loctite Red (do use primer/activator as aluminium and stainless steel need it) you can do 4Nm, without on 3Nm I have had threads being pulled out...

While not so complicated to fix with the right tools and equipment, it's a lot of additional work.

You can directly tap the helicoil thread in the old M6, but will need to adjust the tap, as it should have a flat tip (not pointy)

Loctite Red works perfect.
So does several epoxies (the long 24h curing ones)

Most cells are hand drilled tapped by the Chinese seller..
It's not uncommon to have slightly diagonal studs instead of vertical...

The threads aren't optimal, and the cells aren't intended to be used this way.
It will work, you just need to be careful and use the correct tools.


A simple digital torque meter will set you back $35-40 and probably will safe you many additional hours of work.

 

[Itohmamma]

Ok please teach me.
What the heck are "liquid silicone foam spacers"?
They sound like something I could use as mine are on a moving vehicle.
Thanks you.

LIQUID SILICONE https://www.applerubber.com/hot-top...ou-need-to-know-about-liquid-silicone-rubber/

 

[Itohmamma]

LIQUID SILICONE https://www.applerubber.com/hot-top...ou-need-to-know-about-liquid-silicone-rubber/

I’m of the belief that the corners of a prismatic cell normally Keep their shape and any bulging comes from the large flat sides, the weakest point, which would probably be the center of the cell. By using a full spacer pad, any expansion will have A place of resistance. I chose not to use a solid substrate because during expansion it may cause excessive resistance pressure (I believe usually from the center of the cell) But from everything I’ve read any pressure greater than 17 psi and any part of the cell may cause internal problems.
The correct soft “goldilocks silicone” spacer should meet all compression requirements, and be relatively easy to incorporate in a cell pack. I stated earlier…..to obtain 8psi resistance force, starting approximately 40-50% SOC. I intend to compress them 25% of their thickness, thereby their resistance to expansion of @1mm (according to the liquid silicone foam pad manufacture) will be well within the range of 17 psi resistance.

 

[Deleted member 9967]

I’m of the belief that the corners of a prismatic cell normally Keep their shape and any bulging comes from the large flat sides, the weakest point, which would probably be the center of the cell. By using a full spacer pad, any expansion will have A place of resistance. I chose not to use a solid substrate because during expansion it may cause excessive resistance pressure (I believe usually from the center of the cell) But from everything I’ve read any pressure greater than 17 psi and any part of the cell may cause internal problems.
The correct soft “goldilocks silicone” spacer should meet all compression requirements, and be relatively easy to incorporate in a cell pack. I stated earlier…..to obtain 8psi resistance force, starting approximately 40-50% SOC. I intend to compress them 25% of their thickness, thereby their resistance to expansion of @1mm (according to the liquid silicone foam pad manufacture) will be well within the range of 17 psi resistance.

I just did what the instructions from Eve said to do. Reduce the SOC to about 20%. Then clamp the cells together using no force but just be firm and allow no movement. Now charge them up and they will provide their own clamping pressure.
I know it is stupid to follow the instructions from the people that make the cells. But hey. That is how I am.

Thanks for the link by the way.
Much appreciated.

 

[Itohmamma]

Do you think it’s in the best interest of a Chinese manufacturer to have his product last as long as possible? Well if you do I have a fortune cookie factory I want to sell you so that all your dreams can come true.

 

[Yurtdweller]

We haven't exactly gotten complete and detailed information from the manufacturers regarding compression...
AFAIK, the idea of compressing these cells with a certain force had to do with people in the DIY community becoming aware of a few lines mentioned in some of the lifepo4 cell data sheets which described the life cycle testing conditions.
These conditions are very specific and are very different from the type of service that would be expected in a solar storage application.

It does not make sense to simply extrapolate that 300KGf must be the ideal or required factor to gain long life in the use of these cells for our applications, and as far as I am aware(AFAIK in the english language), there hasn't been any specific guidance on that point from EVE, BYD, or similar manufacturers.

Is there some guidance that a factory engineering team has published about what the best way is to constrain or fixture these cells for long term use in solar storage applications? What published "instructions" about these cells are available from the manufacturers?

Straight from the seller. I believe this document is in the archives.

 

[Yurtdweller]

My personal, somewhat limited experience: bought 16 high-quality (I'm told) EVE lf280k from Shenzhen Luyuan. Built four seperate 12v packs, compressed, charged each individual pack with 60a from solar, THEN disassembled, reconfigured, top balanced, then reconfigured again into 12v packs and bound together with 2 heavy zip ties. Never had any bloating at all. Not when empty, not when full, not during 1/5th C charging. One of my packs is built inside a heavy wooden compression rig with threaded rods, but the other packs are either free-standing or built inside milk crates. I now am running two packs in parallel, so charging never gets much above .09 C. Discharging is usually slower, but I sometimes discharge up to .25 C, when I'm using my 1kw heat gun and other household loads. 6 months in operation.

 

[Yurtdweller]

Do you think it’s in the best interest of a Chinese manufacturer to have his product last as long as possible? Well if you do I have a fortune cookie factory I want to sell you so that all your dreams can come true.

Do you really think Chinese supplier will create a defective product and expect you to purchase from them again? No benefit in producing inferior product with internet reviews and demonstrated quality being constantly reviewed. We all know not to buy Littokala now, right? Even someone buying from liito will not do it twice. The only way to get repeat buyers and new buyers is to produce a solid product. If you have an inferior product, you will only sell to bargain-hunting nubes.

 

[gonmag8]

Straight from the seller. I believe this document is in the archives.

Can't seem to find the document.
Could you please share?

Thanks

 

[Capt Bill]

Flexible Bus Bars if Compressing LiFePO4s ???? I think Frank's LiFePO4 Fire Story Deserves Some Attention on this forum !!!

... I have thought compressing my 8 x 280Ah cells (x 2 or 3 battery banks) would result in cells expanding and contracting at their rectangular cell sides, ... and have thought that solid bus bars would put stress on the battery terminals when such push and shove, and then contraction happens. I have heard comments in other compression thread discussions showing similar thoughts (... just some thoughts). ... I appreciate hearing Frank in Thailand' views because I have seen his story sharing comments over last couple of years showing me lots of experience.

... WOW ... First time I have heard compressing a bloated LiFePO4 could lead to a fire. Re: Frank's "Spontaneous self discharge, one terminal practically molten, lots of damage." Frank : : THANKS for HEADS UP !!! Question: When you mention: "one terminal practically molten" : : Any possibility that molten terminal might have stayed in better shape with a "Flexible Bus Bar"? ... Could Compressing (more, and then more) with Solid Bus Bars make a terminal more susceptible to Spontaneous self discharge, and then spontaneous combustion ??? ... " .... Could solid bus bars on a LiFePO4 set that gets more and more compression (like Frank mentioned), possibly be the cause of a tweak battery terminal (if one did not loosen and re-tighten solid bus bars to reset after each new compression cycle), and then Frank's ... ""Spontaneous self discharge, one terminal practically molten, lots of damage." ??? I am wondering out loud for all of us: Frank: ... Did you loosen, and re-tighten the bus bars on each cycle of your "more and more" compression cycles ??? Wondering Out Loud :+) and with Condolences for that Story.

"Spontaneous Combustion" is something we all (including family and neighbor kids) ... all need to know about, to tweak our habits for safety, especially after paint jobs and deck sealing. IMO: Even oily paper towels in an open plastic trash can under your kitchen counter can cause a fire disaster when no one is there, like those fire created by paint crews leaving their garbage mess at back of building on a wooden deck. ... IMO: Having a small metal trash can for oily trash is a smart in both your shop and home.

... I love learning more all the time, including from other people's mistake. ... While I know I will also be learning from my own mistake ... as the DIYer with my hands on the details ... ;+)

 

[Capt Bill]

ADDED LATER NOTE: after posting this, I got in a personal conversation with Frank about his LiFePO4 FIRE last year; ... then figured out this topic has been thoroughly reviewed / ... I found that 2021 thread by searching for "Fire" with Frank's name. Frank let me know: The Fire was NOT the result of compressing cells while the bus bars were tight. Also saw many possible reasons for the Fire. ... The one I might share was Frank saying: @Will Prowse made a video over bloated cells that he strongly recommend to throw away and never use. With my experience till that time, I challenged that statement, all seemed to be fine, yes? Turns out you are right Will. Bloated cells are not safe. ...

... after study of the older 2021 Fire thread: I would say: I am registering Frank's Fire as him saying ... IMO result of compressing slightly bloated 152AH cells... Spontaneous self discharge, one terminal practically molten, lots of damage. ... Also Picked up Frank's view that those were abused cells; plus older 150Ah lesser cells more susceptible to such mishap, and one of his recent posts said: " ... applied compress some more.. And more.. And.... Fire".

So ... IMO ... Perhaps older Bloated Cells, combined with Compression of those Bloated Cells is a Big No - No to avoid; ... meaning that could possibly cause of a fire. I also just heard another potential angle for a battery fire; ... could also be loose bus bars clamping ... causing big resistance at battery terminal under high amp loads. That's seems like another possible source of heating up enough to possibly ignite a fire ... something to be on top of. ... My Two Cents. ... Thank you Frank for the effort to educate us by sharing all the angles. from ... Bill

 

[RobertGreen]

Straight from the seller. I believe this document is in the archives.

Again that's not from a manufacturer, and suggests that fibra-taping the pack together is an adequate way to apply compression to the cells....
Although this is "monkey see, monkey do," I look at the videos of the automotive manufacturers assembling packs to go into their vehicles, and they mostly appear to use rigid/welded frames which keep the cells rigidly mounted (preventing movement or swelling) and this would prevent movement that would cause stress on the welded terminals. Until there's something more solid to go on, I'm going to keep trying to emulate this type of configuration.

Do you really think Chinese supplier will create a defective product and expect you to purchase from them again? No benefit in producing inferior product with internet reviews and demonstrated quality being constantly reviewed. We all know not to buy Littokala now, right? Even someone buying from liito will not do it twice. The only way to get repeat buyers and new buyers is to produce a solid product. If you have an inferior product, you will only sell to bargain-hunting nubes.

This makes sense, and the other consideration is that we're only getting scraps left over from industry-- the real customer base is automotive and industrial OEMs that purchase huge quantities of the cells and have large engineering and R and D departments that are no doubt testing these cells independently. If chinese manufacturers were deliberately including some type of planned obsolescense or faulty product, presumably they would quickly find themselves out of business. It would be a no-win scenario for the battery maker.

 

[Gazoo]

Straight from the seller. I believe this document is in the archives.

As far as I can recall that document was supplied to Amy Wan by another forum member as a favor to her. It's a basic guide and compression is tricky unless using springs. It's good to keep in mind too much compression is worse than no compression.

EVE has made recommendations for compression and there is an abundant of information on this forum regarding that. I don't know of any other manufacturer that has made compression recommendations with regards to aluminum cased cells.