Moulding in resin?

guess) and

Ordinary polyester resin used for fiberglass can be pigmented - special powders are available but I've had good results using cellulose paint mixed in just before the catalyst. I use beeswax furniture polish as a release agent, but again special stuff made for the job is available. Mould material can be almost anything so long as it doesn't react with the resin - for that size I would probably use plywood as a mould, giving it a few coats of car spray paint and rubbing down between. There are special filler powders that can be added to the resin to make it more robust and chip resistant if that is a potential problem.

AWEM

You can buy battery boxes off the shelf in Maplin

Only for standard batteries.

Chris

Polymorph might be a suitable plastic to use

--Sounds like a lot of trouble. Howzabout bending it up out of aluminum, then if you want line it with duct tape.

Look for "potting resin" or "encapsulation resin" at your prefered electronics supplier, RS, Farnell, Maplin etc. It's usually black and contains filler so is not brittle, it will stick to most things but roughning the surfaces will help.

You can also get "potting boxes" designed for the purpose, spray them with furniture polish, back-to-black etc and they should release if that's what you need. Greg

Just a thought, have you considered that batteries can get hot when discharged / charged & might also want to vent gasses ? worth considering otherwise you might get a split bit of carefully made potted part, or a nasty bang ! I'd be tempted to pot batteries in silicone RTV sealant in a maplins or whatever type box, that should allow some allowance for expansion. Mark G.

If you use silicone rubber for electrical applications or indeed involving most metals,make sure to use electical grade silicones as there do not produce acetic acid when they cure. Standard silicones would otherwise set up a corrosion time bomb with metal parts being attacked.

Bob