Charging 10 XO’s with a Decapus

For a small deployment in Haiti, I was asked to make up a charging harness for 10 XO’s that would charge them from a 12 volt deep cycle lead-acid battery, that itself was charged by a solar panel.

Completed Decapus

Completed Decapus

 

I decided  that I would try to build something that was easily reproducible, repairable in the field, and inexpensive.  Here is the result of that effort:

It starts with a standard 4 inch by 2 1/8 inch deep electrical box ($2.04). Mount 3 bx connectors in three knockout holes to provide strain relief for the input cable, and the two bundles of charging cables.

Cut a small piece of wood, which is a good enough insulator at 12 volts, and two bus bars from aluminum 3/4 by 1/8 flat bar.  Mount the bar overhanging the wood, so that bolt heads, of 1/4-20 3/4 inch bolts, can be inserted up from the bottom, thus exposing the threads for attaching the heavy wire from the battery.

Partially assembled showing wood block, predrilled bus bars, clamps

Partially assembled showing wood block, predrilled bus bars, clamps, and 1/4-20 bolts sticking up

I used self tapping 1/2 inch drill point  screws to attach the 20 individual crimped on spade connector ends that I crimped onto the charging cables (cables were obtained from digikey, part number CP-2199-ND –$1.79 each in quantities of 25). I predrilled the holes in the aluminum.

I don’t trust crimped connections, so I soldered them too.

A little patience, and it's done

A little patience, and it’s done

When connecting the wires to the bus bars, note that the white striped wire connects to the center of the connector and should be attached the positive bus bar.

Each of the 10 XO’s can draw 20 watts. So 200 watts, at 12 volts can sum to about 17 Amps. The #12 gauge wire is permitted inside conduit, bundled with other wires, for up to 20 Amps in the US building code. So free standing, #12 is more than adequate.

Full materials list (mostly from Home Depot):

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