Cell separators. EVA foam vs epoxy sheet

[BigWhiteDOg]

I'm about to start building the box for my battery and wondering what the pros and cons are of 3mm EVA foam vs 0.5mm epoxy sheet (I've got both on my workbench, so availability isn't a concern)

In my mind, the foam option gives the cells a little breathing room as the charge/discharge, but the extra thickness over the epoxy sheet means my 4 pole flexible bus bars no longer span the required distance, so I'd need to get some copper bar and make my own (which isn't the end of the world, and would also mean I can go thicker, but would take more money/time)

Should also mention, it's going in a caravan, so will be subject to a bit of movement if that makes a difference. Would the foam give a little too much over time and leave the cells rattling around?

 

[Suijkerbuijk]

Foam is use against small electrische lost by the outside of the cells
Nothing more , nothing less.

 

[HRTKD]

Should also mention, it's going in a caravan, so will be subject to a bit of movement if that makes a difference. Would the foam give a little too much over time and leave the cells rattling around?

This tells me you should not use foam. Given the Rolling Earthquake nature of an RV, you don't want any cell movement whatsoever.

The cheapest and most commonly available material to use between the cells is flexible cutting board. Many of the vendors that sell LiFePO4 cells will include cell separators as part of the purchase. Mine did and I used them. In fact, they included large pieces of the same material for the sides and top of the cells.

Here is a thread on the topic.

S

Thread 'alternatives to EVA foam?'

Jul 11, 2024

i bought some of the EEL V4 48v battery boxes. they came with EVA foam sheets to put between the cells, these take up room and allow the compression plate to actually have some holding force. i don't like this because the cells aren't actual being compressed, the foam would give way as soon as the cells start to bulge.

what material can i replace the EVA foam with? any good low-cost options? i need a total thickness of 20-22mm in each row of material to replace the EVA foam.

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• Forum: DIY LiFePO4 Battery Banks

 

[rhino]

The correct foam to use is "PORON" foam if you used foam at all.. because what would happen with other foams is it loses its ability to expand after being compressed so many times.. so you could end up with movement like @HRTKD mentioned.

 

[BigWhiteDOg]

I think that's settled then, I'll stick with the epoxy sheets I have and save the foam for another project

The plus side of that is my box will be about 25mm shorter, and my busbars will all fit, so win-win

Thanks all!

 

[Zwy]

Before Poron, I used neoprene. I've had neoprene in my truck camper for 10K miles on some of the roughest terrain and roads.

Use Poron and compress 25% of the thickness of the foam and the cells will not move. Do use the adhesive and stick the Poron to the cells.

 

[nosys]

if your concern is to put something between cells that would resist well temperature without being thick enough to cause problem with standard busbar, you can try thick Nomex Paper (Type 410), that is commonly use in industrial heavy electric device (like transformers in train) as insulator

 

[robbob2112]

Poron between cells and compress as described with springs at one end to let them expand and contract... then make sure to either put the battery on a box or secure it in a manner that doesn't let it slide around...and make sure the battery is sitting on something smooth like either epoxy board or more poron... Just make sure when securing it nothing but the end clamps are applying pressure anywhere...

Recently say a picture of a vented cell because it was sitting on plywood and a defect of the wood rubbed the bottom.

 

[Zwy]

Poron between cells and compress as described with springs at one end to let them expand and contract... then make sure to either put the battery on a box or secure it in a manner that doesn't let it slide around...and make sure the battery is sitting on something smooth like either epoxy board or more poron... Just make sure when securing it nothing but the end clamps are applying pressure anywhere...

I used fiber cement siding on the shop system.

Recently say a picture of a vented cell because it was sitting on plywood and a defect of the wood rubbed the bottom.

In my house is plywood but it was sanded and painted before cells were installed. Back then I could not source fiber cement siding due to covid supply chain issues. Sanded and painted will work.