Material for building battery box

Mattster · 22 January 2022, 12:04

I'm planning to build a new battery box for a 24ah LiFePO4 battery. Not really much available at the right size, and it needs to be solid enough to mount a 9 inch finder on the top, and also tailored to fit around my seat, so I think making something is going to be the best option.
I'm thinking HDPE, just because I haven't got any experience of working with other plastics. Plywood is an option too, I suppose, but would need a bit of finishing.
Before I take the plunge and buy a suitable sized sheet of HDPE (10mm?), which will cost about £30, are they any other suggestions? Will HDPE be suitable for what I want? Any other suggestions? Plan is just to butt join with stainless screws, nothing fancy. Battery shouldn't need to come out too often, so probably no hinges etc.

Pikey Dave · 22 January 2022, 15:36

Quote:

Originally Posted by Mattster

I'm planning to build a new battery box for a 24ah LiFePO4 battery. Not really much available at the right size, and it needs to be solid enough to mount a 9 inch finder on the top, and also tailored to fit around my seat, so I think making something is going to be the best option.

I'm thinking HDPE, just because I haven't got any experience of working with other plastics. Plywood is an option too, I suppose, but would need a bit of finishing.

Before I take the plunge and buy a suitable sized sheet of HDPE (10mm?), which will cost about £30, are they any other suggestions? Will HDPE be suitable for what I want? Any other suggestions? Plan is just to butt join with stainless screws, nothing fancy. Battery shouldn't need to come out too often, so probably no hinges etc.

It’ll need sealing as lithium batteries & water are a bad mix. You’ll struggle to use any kind of sealant on HDPE, so it’ll have to be a mechanical seal or welded.

Oldman2 · 22 January 2022, 15:45

Does it have to be a hard box? I used an insulated cooler lunch bag 24 x 15 x 2 cm.
It was around £6 and has a nylon zip so shouldnt rot from salt too quickly. It was big enough for my 10x7x9cm 7.2Ah LiFePO4 battery. It also serves to store my head unit when its being transported. The handle straps are just the right length to keep it all secured over my Elling seat.

45DV on my Elling.jpg

jeffstevens763@g · 22 January 2022, 16:17

Why not buy a box

https://www.solentplastics.co.uk/9-l...-without-foam/

jeffstevens763@g · 22 January 2022, 16:18

Double post

Steve509926 · 22 January 2022, 18:37

https://www.rib.net/forum/f37/not-fo...g-86842-2.html

Hi Matt, take a look at post 40. Other box sizes are available.

Mattster · 22 January 2022, 21:44

Thanks all - some good pointers there. The Solent plastics one looks OK, but I wonder if robust enough on top to mount sounder directly? They are a good company tho, have bought a few bits from there in the past.

Your box looks good Steve, although by the time you make a solid surface for the top etc I wonder if making the whole box is that much more effort? At least when making one it can be exactly the right size, and designed to fit the seat exactly as well.

To seal it I'd probably just use a low adhesive silicon and hope that it acts as a liquid gasket with screws holding it together - it shouldn't really need to stick. Planning in LiFePO4 so the least dangerous of the lithiums with respect to water (and everything else) I believe, but obviously wouldn't want water getting in there.

Steve509926 · 22 January 2022, 22:01

Matt, you give me far to much credit "make solid surface for the top" - it's two IKEA chopping boards screwed together at one end and bolted together to clamp on to the seat at the other.

jeffstevens763@g · 22 January 2022, 22:07

There as good as pelican cases but much cheaper very strong easily hold chart-plotters etc

duckpond49 · 24 January 2022, 14:13

I do a variety of marine "boxes" and prefer expanded PVC over HDPE. It's a third cheaper, and a third lighter. It also glues extremely well with standard PVC plumbing adhesive (but use clear "cleaner", not the purple stuff)
It will scuff a bit though, so not a great choice if it is in a spot where it will get banged and kicked a lot.

Mattster · 24 January 2022, 15:21

Thanks Duckpond, I had no idea about this stuff. I see you are in the USA, but it looks like we have brands Foamex, Foamalite, Forex and Palight in the UK, which are apparently all the same thing. Do you have the same? Just want to check it is the same stuff. Looks like thickest we have is 10mm. Do you think this could handle mounting a 9" finder on top? Could always double up, or put a bit of HDPE or similar inside. I like the idea of this stuff and I have the PVC plumbing glue already.

jeffstevens763@g · 24 January 2022, 15:23

You can buy IP rated junction boxes which are strong or make one out of fibreglass, lay up glass panels on a piece of window glass then trim and fix together with fibreglass strips.