Building the battery box

So I’ve started building the new battery box at home. So far just a dry assembly. All the timber will be sanded and epoxy coated before using epoxy to glue as well as screws.

Apart from the plywood base (left over from settee bases) the rest of the wood comes from old Ikea bed slats.

Among the complications is the access. I’ve built as much as I can that will actually (hopefully) fit through the cockpit locker opening. This will be fixed into the extended original battery box and so will hold the batteries from moving forwards, backwards or side to side. Once all in place I’ll fix slats to stop them falling out if we ever get knocked right over.

Here you can see all that can be pre-assembled. The cockpit locker opening is about half the length.
First battery will be lowered in and slide forwards
Battery 2 goes straight down through the hatch.
Slats added to hold battery 1 down and provide a platform for battery 3
Battery 3 in position (fills the remaining space above battery 1). It does go a bit further forward as it isn’t blocked by the diesel fuel line.
Looking from above you can see all the battery terminals and the little Battery Management System displays.

The smaller battery for engine starting (which is still Lead Acid because it doesn’t need all the fancy features of Lithium) will be on the aft end (left in the pictures) on the top of battery 2. It will be in a sealed plastic box as unlike the Lithium batteries can leak.

Once all these batteries are all in place I’ll fix the busbars (copper bar that the battery terminals connect to) above forward end of battery 2 (right next to the lead acid battery box so they don’t cover battery 2’s terminals). 6 identical cables (3 red and 3 black) connect the batteries to the busbars (this way we can ensure the batteries are evenly charged and discharged).

From the busbars for our supply we run 2 big cables for +ve and 2 for -ve to the main switch , due to the high current demands. The -ve cables will have a shunt in them (used to measure battery condition and use). From the main switch we go onward to the inverters, windlass and 12 volt system.

Also from the busbars we will run a slightly smaller pair of cables to a common connection point for all the solar and wind controllers (that keeps the cable runs to the batteries much shorter).

Once the cabling is in then I’ll add a waterproof top and seal it off from the cockpit locker and engine compartment (with sound insulation to the engine side).

Quite pleased with this. The main struggle at the moment is to find a supplier for tinned copper bar (50mm x 6mm should be about right) to make the busbars from.

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