What battery material enclosure is recommended? Steel or plastic?

I have a custom made stainless steel enclosure (like a deep tray with a topper).

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But I was wondering whether the enclosure material is important. Westmarine sells the cheap plastic ones. There are also the ones in your website that are powder coated steel but they are expensive for a small cabin application.

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Could you share some insight?

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I plan to put a bank of 100-200 cells outdoor in a large metal waterproof box. Are there any issues with the LIFEPO4 that require venting? can I put in a Water/Airtight configuration?

I need figure out whether I need plan put vents on the box holding the batteries or not.

Thanks

You can seal them in a box so long as that box is not going to be in a hot environment.
You do need some kind of opening to vent gas in case the cells start to go critical and Vent Gas into the box.
If the metal case is totally sealed it could explode open if something went wrong. Many LFP batteries are water tight sealed but most of those use plastic cases that probably have a weak point that will burst open under pressure.
The Fortress eFlex is probably a good example of what you are trying to build. Even though it is metal and totally air tight sealed it has a pressure relief valve on the front. If you look at the "rack" style batteries, you won't normally see vents in the design. The cells themselves will only vent in a failure, so there is no need to provide ventilation to the enclosure. You do need to try to keep them at a comfortable temp since it can impact the overall lifespan of the cells.
I wanted my cells in a completely metal enclosure to reduce the risk of fire, so that might be something to think about in your application as well.

If you look at the "rack" style batteries, you won't normally see vents in the design. The cells themselves will only vent in a failure, so there is no need to provide ventilation to the enclosure. You do need to try to keep them at a comfortable temp since it can impact the overall lifespan of the cells.
I wanted my cells in a completely metal enclosure to reduce the risk of fire, so that might be something to think about in your application as well.

Rack style batteries are not airtight enclosures.

If you look at the "rack" style batteries, you won't normally see vents in the design. The cells themselves will only vent in a failure, so there is no need to provide ventilation to the enclosure. You do need to try to keep them at a comfortable temp since it can impact the overall lifespan of the cells.
I wanted my cells in a completely metal enclosure to reduce the risk of fire, so that might be something to think about in your application as well.

Rack style battery packs are not waterproof, except for the eFlex. Waterproof is what the OP wants.

You can seal them in a box so long as that box is not going to be in a hot environment.
You do need some kind of opening to vent gas in case the cells start to go critical and Vent Gas into the box.
If the metal case is totally sealed it could explode open if something went wrong. Many LFP batteries are water tight sealed but most of those use plastic cases that probably have a weak point that will burst open under pressure.
The Fortress eFlex is probably a good example of what you are trying to build. Even though it is metal and totally air tight sealed it has a pressure relief valve on the front.

Resurrecting: Do you know what psi the relief valve should be? I can't find that info anywhere.

Resurrecting: Do you know what psi the relief valve should be? I can't find that info anywhere.

We have an ePropulsion electric outboard with IP67 battery box, I just went and had a look at the valve on that, but I didn't see any markings in the dark and rain, although I took some pictures in case it helps.

I would guess any relatively low differential pressure release valve should work, you see them on the airtight plastic flight cases often found in army surplus stores too, but I guess they are plastic normally, and you'd probably want a metal one with the silicone seals.







Cool, thanks! Yeah, I was thinking around 10 psi should work. In the event it was ever needed, I would think there would be way more than 10 psi coming out of the battery.
Thanks again, I'll see if I can hunt that one down too

Cheers A general note. LFP does not off-gas unless it fails. it is not FLA that off gasses regularly. No active or even passive venting is required. Look at all the Sealed Battery Packs in ABS plastic cases, no vents, not even server/telecom rack models.

The battery packs we handle do not have any vents either.
Sorry I do not promo the business here "ever".

...LFP does not off-gas unless it fails....

The battery packs we handle do not have any vents either.
Sorry I do not promo the business here "ever".

Our battery boxes are not air tight steel pressure vessels though. I don't know if it's overlooked in the smaller sealed plastic cases, or unnecessary until the one in a million catastrophic cell failure, maybe the pressure released isn't enough to crack a plastic case let alone a steel one, but for some reason ePropulsion have a pressure release valve (*edit they call it a 'Vent valve') on their airtight/ watertight case?

Resurrecting: Do you know what psi the relief valve should be? I can't find that info anywhere.

No clue but I would think that just a bit above Zero PSI would be the goal.
I see One PSI vent valves for sale.
The pressure in and outside of the case would always be roughly the same, so any excess would mean gas venting is happening inside and so an outside vent is needed to release that quickly.

Our battery boxes are not air tight steel pressure vessels though. I don't know if it's overlooked in the smaller sealed plastic cases, or unnecessary until the one in a million catastrophic cell failure, maybe the pressure released isn't enough to crack a plastic case let alone a steel one, but for some reason ePropulsion have a pressure release valve (*edit they call it a 'Vent valve') on their airtight/ watertight case?

Fortress eFlex batteries are sealed pretty tightly. The Top and bottom are put on with Silicone Sealant and even the Switches and Ports have rubber gaskets on them.
Even with that I am pretty certain that they are not air tight, just very water resistant from Rain etc.
The vent valves are there just in case a massive surge of pressure happens and it cannot escape fast enough from all the little gaps.

I don’t think you need a vent.

Here is an example of a waterproof battery which I doubt is vented :


And people practically sit on top of these in their golf carts so you would likely have heard if they’re problematic.

Just because a Chinese company makes it that way it does not mean it’s safe!
Watch any of the countless videos on LFP batteries out gassing and it’s pretty clear that a lot of gas is produced. A sealed container with pressure building up is pretty much the definition of a bomb.

Just because a Chinese company makes it that way it does not mean it’s safe!
Watch any of the countless videos on LFP batteries out gassing and it’s pretty clear that a lot of gas is produced. A sealed container with pressure building up is pretty much the definition of a bomb.

Or someone should tell all the cell manufacturers they don't need to bother putting vents in prismatic cell cases...