Having manufactured many things over many years, i decided to post one of them, it is a portable battery pack which can be removed from the vehicle to power other equipment remotely from the vehicle, this one was designed for camping and working, but could be put to many other uses. For camping it powered the fridge in the tent, and lighting at night inside and outside the tent.
The battery was a 220 amp leisure battery, it is housed in a glassfibre box and has a number of standard sized fused and unfused sockets for connection to various items.
The battery was measured and the dimensions of the box were established, two moulds were made from casting plaster and sanded very smooth, they were finished with lacquer to seal the plaster and they were polished to a very high degree with ordinary household polish, this was built up through several coats and polishes. PVA release agent was applied to the mould for the base, it was laid up with a gel coat which was alowed to tack off, fine fibreglass matting was applied and polyester resin was applied, two coats of fine mat were applied and allowed to nearly harden, then three coats of coarse mat and coats of polyester resin were built up to give it thickness.
Reinforcing members were made, these were just strips of "U" shaped cardboard packing which were covered by two coats of polyester resin and coarse matting, these were allowed to dry and cut to fit inside the floor of the box base, then just resined in and covered with a coat of resin and matting.
Making the lid was exactly the same, although a slightly more complex plaster mould was necessary as it incorporated a carrying handle.
The battery was placed in the box and measured for height, four "L" shaped metal brackets were cut and fibreglassed in the right position, these housed metal straps for holding the battery down, then the two retaining straps were made from steel, and the battery was firmly mounted in the base of the box.
Bulkhead sockets were purchased from Vehicle Wiring Products, the box base was cut to accept them, and they were installed and wired, a 6 way fuse box was also purchased and installed inside the box, it contained 4 X 5amp fuses and 2 X 10 amp fuses leaving us with 6 fused outlets.
One unfused outlet was installed, this is for charging the battery only, and is a different socket to the others.
The lid was placed onto the base and marked, this was drilled with 6 X 6mm holes through the lid and base flanges, which are quite thick, 6 brass ferrules were turned on the lathe and tapped 6mm, the base holes were drilled out to 9mm and the ferrules inserted from the bottom and epoxied in to position.
From my "O" ring kit i found some nice sized O ring rubber so a made a seal for the lid, 6 M6 screws were used to secure the lid in position to the base.
Simply place in the vehicle and plug into the unfused connection to charge, unplug and remove from the vehicle, plug whatever appliance you want to into the nice safely fused outlets to power what you want while camping.