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

Surferdudemi

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Dec 18, 2020
Messages
117
High C-rate is mostly creating larger heat then slow charge.

For compression, the thin aluminium walls casing (not CalB) is NOT intended for home use.

It is intended to have structural strength improvement form manufacturers

That's us now... Manufacturer.
Adding a di-electric sheet is always smart. Anti-static plastic would work great.

Casing won't make a short it's negative, if conductive at all.
Even then..
It won't hurt. The thin blue plastic is not really high capacity protection.
(280Ah is in my book high capacity)

Side compression..
Not so important.

The compression is there to prevent delamination.
Delamination does 2 things:
- reduce battery capacity
- increase risk of instant selfdischarge: all contained current converted to heat.

Once bloated....
It's not as safe as it was before bloating.
Slightly bloat, like about one mm., Not a problem.
Large bloat like over 3mm....
Challenges!

Best is to mimic the factory original construction with the materials at hand.

Instant selfdischarge will reach temperatures way over 500c, (but under 660C) infection the neighbor cells, and perhaps enough heat to self combust the plywood.
Or (di-electric) grease, what usually starts to ignite at 350-450C
Although both cases of adjacent batteries are negative for each cell, if you electrically connect two of them, you're effectively shorting one of the cells if the positive of one is connected to the negative of the next. Hence my concern. I found some scrap T-slot extrusion at my hackerspace, which I think are about the right lengths to make a frame around a bank of cells, so I think I've got the external compression solved. I don't plan to used these cells at more than about 1/2 C rate, so maybe heating won't be a problem. Just saw some thermal images of cells showing most heating was interior, and seemed like the larger flat sides would be the best place to remove heat. So perhaps over-engineering as usual, LoL.
Thanks!
 

cinergi

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Messages
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Although both cases of adjacent batteries are negative for each cell, if you electrically connect two of them, you're effectively shorting one of the cells if the positive of one is connected to the negative of the next. Hence my concern. I found some scrap T-slot extrusion at my hackerspace, which I think are about the right lengths to make a frame around a bank of cells, so I think I've got the external compression solved. I don't plan to used these cells at more than about 1/2 C rate, so maybe heating won't be a problem. Just saw some thermal images of cells showing most heating was interior, and seemed like the larger flat sides would be the best place to remove heat. So perhaps over-engineering as usual, LoL.
Thanks!

You definitely won't have heating problems from the cells themselves. At 200 amps discharge and 140 charge (100 - 0 - 100 percent SoC) I saw a 10F rise in temp.
 

Capt Bill

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Redwood Valley, Cailfornia/ Montezuma, Costa Rica
Adding a di-electric sheet is always smart. Anti-static plastic would work great.
Wonder if a sheet of ABS plastic would be in category of "di-electric" (new term to look up). I also wonder a what potential stressed are put on the battery terminals of 280Ah EVE cell by those solid bus bars they seem to most oftern be supplied with; ... when the battery changes slightly in dimensions on higher amp charge or discharge cycles (from the heat up). ??? Do you have any thoughts about that question ? :+)
 

fhorst

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Flexible cutting boards, are they fire resistant?
If so, sure, go for it!!
If not... That probably will be the difference between burning your house down or just loosing your battery pack.

****

Lol.
When I first read the term on the tube...I needed to look it up also,
Only to discover that it is non conductive grease... ????

Counterintuitive product!!

Anyways, grease for electric contacts, light bulb, etc. are called di-electric grease.

The thin layer after good contact is so thin, it doesn't have any negative effect on the electric conductivity.
While it does not get affected by electricity.
For aluminium, ox-gard and novalex (?) Are considered to be market standard, approved by most inspection regulations.

Yes, I have an answer on that bus-bar question.

This is how my new battery looks like:
IMG_20210720_185113_238_copy_768x432_1.jpgIMG_20210720_185136_935_copy_768x432_1.jpg
And this is the only good connection method.

2021-7-20 18-53-46_copy_432x836_1.jpg
Laser welding....

Now most of us, including me, don't have this equipment and the knowledge how to use at home.

So we mimic, and try to get as close as possible to the product the professional battery builders do.
(Aka factory)

In this situation BYD 24v (S8) 260Ah pack, 2x (S16) + Jikong BMS about $1300 including transport and all tax.
(About $80 per cell, without the troubles and include BMS)

Here is the catch...
Thailand only (for now)

Due to my misfortune (fire) (perhaps due the use of rigid Bus-bars?) I'm now the happy owner of 6 of these 60Kg babies, 40 kWh.

If it where only have been available when I started 18 months ago....

Anyways.
It wasn't and I had 18 months fun (and sad times) tinkering.
Now that's your turn.

All you can do is mimic this build as close as possible.

See the massive size of the aluminium Bus-bars.

The end terminals have laser welded nickel sheet to the aluminium.
Not really an option for us, but we can electroplate aluminium with nickel, if needed.
Most of the lugs people use are factory plated, and ready to go onto aluminium.

Rigid isn't a problem , as long as it has this type of spring shape, it can expand /contract with the terminals/cells without place real force on it.

We are already starting on a quicksand base..
Building our palace in a swamp...

Drilling holes in aluminium terminals that are NOT intended / designed to be used like this.

Drill a hole in the terminal of your car battery tap thread and connect the wires on it.
Besides that you probably end up melting the lead, you won't pass any (MOT) gouvernement inspection.
Guess why would that be...

I'm pointing out the obvious.
We are playing with things outside specifications and outside what is considered normally to be safe operation.

It can be safe, just be extremely careful.
Use grubscrew/studs (not the screws they shipped) with Loctite red and mandatory primer (aluminium and stainless steel are "inactive" metals for Loctite, without primer it's nothing more then "strong" glue, that does increase total strength a tiny bit. With primer?
You twist out the Terminal before the grubscrew will let go...)

Bus-bar, aluminium!
And why not?
No problems with galvanic corrosion.
And "easy" to bend in this spring shape.
Making it flexible enough.

If you do want copper?
2 options
1. Spring shape.
2. Heat it till glowing almost white (close to melting point) and let it cool down slowly.
Quick cooled copper is rigid, strong.
Slowly cooled is as flexible/soft as lead.


Edit: Oepsie my bad.
Other way around.
Quick cooled is flexible, slow is rigid.

This is also the difference between rigid and flexible copper wires (besides the thickness of the threads)

Or.. just use as is.
Compress as it's needed to prevent delamination, clean the terminals, place the Bus-bars, tighten the M6 nuts with a torque meter (4Nm) and keep the temperature stable, not too high capacity (under 100A) to prevent temperature difference.

This probably will work for many many years

Outside specifications or normal protocols, but works.
Or not.. and join my misfortune.
 
Last edited:

Supervstech

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Staff member
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Sep 21, 2019
Messages
6,243
Flexible cutting boards, are they fire resistant?
If so, sure, go for it!!
If not... That probably will be the difference between burning your house down or just loosing your battery pack.

****

Lol.
When I first read the term on the tube...I needed to look it up also,
Only to discover that it is non conductive grease... ????

Counterintuitive product!!

Anyways, grease for electric contacts, light bulb, etc. are called di-electric grease.

The thin layer after good contact is so thin, it doesn't have any negative effect on the electric conductivity.
While it does not get affected by electricity.
For aluminium, ox-gard and novalex (?) Are considered to be market standard, approved by most inspection regulations.

Yes, I have an answer on that bus-bar question.

This is how my new battery looks like:
View attachment 57634View attachment 57635
And this is the only good connection method.

View attachment 57636
Laser welding....

Now most of us, including me, don't have this equipment and the knowledge how to use at home.

So we mimic, and try to get as close as possible to the product the professional battery builders do.
(Aka factory)

In this situation BYD 24v (S8) 260Ah pack, 2x (S16) + Jikong BMS about $1300 including transport and all tax.
(About $80 per cell, without the troubles and include BMS)

Here is the catch...
Thailand only (for now)

Due to my misfortune (fire) (perhaps due the use of rigid Bus-bars?) I'm now the happy owner of 6 of these 60Kg babies, 40 kWh.

If it where only have been available when I started 18 months ago....

Anyways.
It wasn't and I had 18 months fun (and sad times) tinkering.
Now that's your turn.

All you can do is mimic this build as close as possible.

See the massive size of the aluminium Bus-bars.

The end terminals have laser welded nickel sheet to the aluminium.
Not really an option for us, but we can electroplate aluminium with nickel, if needed.
Most of the lugs people use are factory plated, and ready to go onto aluminium.

Rigid isn't a problem , as long as it has this type of spring shape, it can expand /contract with the terminals/cells without place real force on it.

We are already starting on a quicksand base..
Building our palace in a swamp...

Drilling holes in aluminium terminals that are NOT intended / designed to be used like this.

Drill a hole in the terminal of your car battery tap thread and connect the wires on it.
Besides that you probably end up melting the lead, you won't pass any (MOT) gouvernement inspection.
Guess why would that be...

I'm pointing out the obvious.
We are playing with things outside specifications and outside what is considered normally to be safe operation.

It can be safe, just be extremely careful.
Use grubscrew/studs (not the screws they shipped) with Loctite red and mandatory primer (aluminium and stainless steel are "inactive" metals for Loctite, without primer it's nothing more then "strong" glue, that does increase total strength a tiny bit. With primer?
You twist out the Terminal before the grubscrew will let go...)

Bus-bar, aluminium!
And why not?
No problems with galvanic corrosion.
And "easy" to bend in this spring shape.
Making it flexible enough.

If you do want copper?
2 options
1. Spring shape.
2. Heat it till glowing almost white (close to melting point) and let it cool down slowly.
Quick cooled copper is rigid, strong.
Slowly cooled is as flexible/soft as lead.


Edit: Oepsie my bad.
Other way around.
Quick cooled is flexible, slow is rigid.

This is also the difference between rigid and flexible copper wires (besides the thickness of the threads)

Or.. just use as is.
Compress as it's needed to prevent delamination, clean the terminals, place the Bus-bars, tighten the M6 nuts with a torque meter (4Nm) and keep the temperature stable, not too high capacity (under 100A) to prevent temperature difference.

This probably will work for many many years

Outside specifications or normal protocols, but works.
Or not.. and join my misfortune.
If those are like my BYD packs, the aluminum isn’t bent into that shape… it is a pack of several paper thin sheets of aluminum welded together at the ends… SUPER flexible.
 

ken morgan

Solar Addict
Joined
May 11, 2021
Messages
370
I am serously rethinking my 6 mm x 30 mm busbars. Last night i went ahead and ordered a bunch of three inch 180 ft/lb springs. if any of the prior calculations are correct,(and I did not screw up my attempts at repeating some of you folks work) then the springs i ordered when compressed by 1" should give me about 5 PSI at 50% charge and it should ramp up as it increases to full charge. my cells are plastic 200 amp calb cells and currently have no bulges that I have noticed, however an once of prevention...

I commissioned this pack three weeks ago. with a finger tight aluminum plate on the front and back and six 8mm threaded rods holding them together. I guess I could spring for a couple hundred 2 gauge crimp terminals and some wire, even though I was trying to avoid that due to the intense PITA it prevents on crimping 60 some odd terminals for this one pack.

Is it worth the effort to solder the terminals after crimping? It seems to me that it would be a PITA to keep the insulation from burning while trying to heat up a terminal that big and the wire, though I am wiling to try out one or two to see how it works.
 

Mcgivor

Solar Addict
Joined
Jul 24, 2021
Messages
187
This thread is interesting despite my not having EVE cells, primarily because it raises questions which I have come across during my research phase. The first involved the useage of higher capacity cells as opposed to lower in a parrallel configuration, the recommendation was that the preference was to use lower capacity due to the effects of gravity and outer case distortion.

The second was cell orientation, from the information i gathered, LiFePo4 cells should be mounted terminal/vent up, not on their sides, the CALB installation manual clearly echoes this, the point brought up due to the mentioned side mounting proposal earlier.

Clamping in general terms was to prevent inter cell movement thereby reducing stress on the terminals, particularly in mobile applications.

Reading between the lines, it may be EVE modified their recommendations to compensate for structural inadequacies in lue of changing the design of the outer case.

Personally I have 32 100Ah no name cells, along with some 200Ah CALB cells, the quality of the CALB is superior in every aspect especially the case construction and we're less expensive 2 years later.

Naturally all the above is information gathered, which may include opinions of others, but it is interesting none the less.

Attached is the CALB installation manual for those who may be interested
 

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Sojourner1

Itinerant
Joined
Sep 30, 2019
Messages
581
Location
USA
This thread is interesting despite my not having EVE cells, primarily because it raises questions which I have come across during my research phase. The first involved the useage of higher capacity cells as opposed to lower in a parrallel configuration, the recommendation was that the preference was to use lower capacity due to the effects of gravity and outer case distortion.

The second was cell orientation, from the information i gathered, LiFePo4 cells should be mounted terminal/vent up, not on their sides, the CALB installation manual clearly echoes this, the point brought up due to the mentioned side mounting proposal earlier.

Clamping in general terms was to prevent inter cell movement thereby reducing stress on the terminals, particularly in mobile applications.

Reading between the lines, it may be EVE modified their recommendations to compensate for structural inadequacies in lue of changing the design of the outer case.

Personally I have 32 100Ah no name cells, along with some 200Ah CALB cells, the quality of the CALB is superior in every aspect especially the case construction and we're less expensive 2 years later.

Naturally all the above is information gathered, which may include opinions of others, but it is interesting none the less.

Attached is the CALB installation manual for those who may be interested
No attachment ?
There is a resource section that has miscellaneous info.

Here is the CALB section. https://diysolarforum.com/search/451149/?q=Calb&t=resource&c[title_only]=1&o=relevance
 

Firstascent

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Joined
Mar 7, 2020
Messages
149
I decided to make a full enclosure:

View attachment 15537



  • Have aluminum flatbars and "T" extrusions to allow some airflow betwen cells, so heat wont be much of a problem.
  • Can mount both horizontallly and vertically, also could fix to the wall.
  • Can "easily" transport the full pack to connect between systems. (Probably not needed for a lot of people, but usefull for me).
  • Can easily change the BMS, as the leads are connected to a connection bar.
  • Looks better!
And as you can see, i have 4 x threaded rods in the design, so i can put the 300KGF if i want, in practice i just compress them a bit as i dont know how to calculate or measure that... i guess you can calculate that with a torquimeter or just measure with a pressure plate.

The cell walls stay completely flat with the middle flatbars and resistant aluminum structure in both sides.

So far im happy with the build!
I just spent way more hours than expected reading through all 31 pages haha. I really like what @mrdavvv did and had something similar in mind as I want to build mine out of aluminum as well for my RV (I have 16, 280ah eve cells) but wouldn't do an full enclosure.

Not to pick yours apart sir as I think you did an excellent job, but I have some questions I just am not sure on as I plan out how I want to build my aluminum case.

1. With the 3 points of contact in-between each cell, do you feel they are close enough together that no bulging would happen in the empty space?

2. With all the talk on foam/padding etc in between each cell would you all not do that in this type of design, maybe only at the end plates?
 

lance

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Messages
115
Man, this thread got long and dense! I was hoping just to find if there's been any general consensus found regarding to place a thin padding between each cell so as to allow SOME but, MINIMAL expansion and contraction. It seems there's a fairly solid consensus on the need to clamp and apply pressure, both for the sake of the above issue but, also to prevent shifting in a mobile application, and thus stress on busbars/terminals. My thinking right now is to go with a square of 1/16" neoprene, (https://www.amazon.com/NEOPRENE-pro...eywords=neoprene+sheets&qid=1629393184&sr=8-8),
lightly adhered to the center of the cells in between each so as to allow some expansion but, minimize it, and also to allow some airflow around the cells. Getting close to top balancing my 8 280ah/3.2v cells and doing a final assembly of this pack. I would welcome anyone's thoughts/conclusions, expert or otherwise on the topic!
 

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HRTKD

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Somewhere South of Denver
My opinion is that a non-rigid spacer is counterproductive. You're clamping them to prevent movement. Why would you put something in place that would then allow movement?

If I put anything between my cells, it will be to prevent thermal transfer and it will be rigid.
 

Firstascent

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Messages
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@lance have you started top balancing already? I have 16 cells of the same, about to hit two weeks and up to 3.385 volts 🤣 getting closer. I hear from 3.4-3.5 and then 3.5-3.5 should be quicker. I’m hoping so haha
 

lance

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Messages
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My opinion is that a non-rigid spacer is counterproductive. You're clamping them to prevent movement. Why would you put something in place that would then allow movement?

If I put anything between my cells, it will be to prevent thermal transfer and it will be rigid.
I get that but, I'm talking about essentially a total of 3/16" possible movement (with 1/6" pad) or, 3/32" possible movement (with 32"pad). And, look at the container they're in..... perhaps not well documented but, those batteries are NOT moving!
 

lance

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Messages
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@lance have you started top balancing already? I have 16 cells of the same, about to hit two weeks and up to 3.385 volts 🤣 getting closer. I hear from 3.4-3.5 and then 3.5-3.5 should be quicker. I’m hoping so haha
Oh man.... you're scaring me! No, I've not; only read about the process. I'm still aways off from them actually becoming active, and someone on here recommended waiting for the top balance until they were close to being put to use.
 

Firstascent

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Messages
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Oh man.... you're scaring me! No, I've not; only read about the process. I'm still aways off from them actually becoming active, and someone on here recommended waiting for the top balance until they were close to being put to use.
I'm not exaggerating on the time either :( you're 8 cells should theoretically take 1/2 the time but it's still a long time! It's also important to note I'm using a 10A power supply. So if you can find a larger 30A supply then that would speed up the process as well.

also yes I believe you don't want to keep these at a max state of charge for too long which is why you shouldn't top balance them and leave them at 3.65v for months.

Another thing you can do is put your pack in a 4s 12v battery config and use a 12v charger to charge them most of the way up to speed up the process. I'm following the latest recommendation of top balancing to 3.4, then to 3.5, then to 3.65 in steps and not straight to 3.65. So if you use a 12v charger then just stop before it gets to 3.4v.

to not get too far off topic :) as far as padding etc in-between cells, I think at most some people recommend something very thin to avoid any chafing between the cells. but I also think that is highly unlikely if they are properly secured from whatever "compression" box you are using. For mine I've decided on an aluminum compression box and I'll have some type of non-conductive barrier between the end of the cells and the aluminum end piece.
Since my setup will be mobile (RV) I'm undecided whether I'll do some type of barrier between the cells. If I do, I was thinking something very thin with a little "grip" to it like a piece of 3M vinyl/clearbra type material. But that would be just extra assurance nothing moves or rubs, not for airflow.
 

Short_Shot

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Neoprene isn't exactly the best choice.
 

HRTKD

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My two 4s batteries are in my bumper pull toy hauler (11k GVWR). I get down some rough roads, drive on some highly off-camber roads and look forward to getting into a camping spot that requires 4Lo. I had the opportunity earlier this year to verify that all the screws on my cell terminals were still tight. Only one screw required a small amount of tightening. I'm using no thread locker or lock washers.

Maybe one day I'll take the packs apart and see what the surface between the cells looks like. But based on the screws being secure after all I've put the batteries through, I doubt that I'm going to see any evidence of friction/movement between the cells.
 

Firstascent

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Messages
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My two 4s batteries are in my bumper pull toy hauler (11k GVWR). I get down some rough roads, drive on some highly off-camber roads and look forward to getting into a camping spot that requires 4Lo. I had the opportunity earlier this year to verify that all the screws on my cell terminals were still tight. Only one screw required a small amount of tightening. I'm using no thread locker or lock washers.

Maybe one day I'll take the packs apart and see what the surface between the cells looks like. But based on the screws being secure after all I've put the batteries through, I doubt that I'm going to see any evidence of friction/movement between the cells.
this makes me feel good haha! I have a 42' fifth wheel so I try to avoid the rough stuff (although that's where the best spots are) but with this size makes it difficult lol. But good to know yours have held up to some 'normal' abuse
 

lance

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Neoprene isn't exactly the best choice.
I like the look/sound of that but, my understanding was that there was also a desire to have some air movement between the cells, whether for cooling or for heat transfer from heating pads in extreme cold.
 
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