A box for the battery. This one is being built into the (dummy) boiler water tank underneath the loco. Originally the plan was to install the battery in the engine room but space in there is starting to get restricted and we wanted the vacuum exhausters to have a bit of space between them - see update from a couple of months ago - so the battery is now going outside instead. They fit pretty much perfectly into the dummy tank and only a minor modification needs to be made to the tank frame to hold the battery.

These six pieces of parallel-flange channel form the bracing / support for the inner of two angles which will take the weight of the battery. With a notch at 32 degrees cut to allow them to bend and a section removed to allow them to sit flat, they've already been descaled and had the burrs taken off.