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.
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.
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.
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):
- Teks 8×1/2 pan/drill pt (300 pcs) $5.48
- Mach scr rnd hd 1/4-20 $1.18
- #6×4/8 zinc fl hd phil wood screw $1.18
- 22-16AWG/34-6 spade terminals 75pk $6.97
- 48″x3/4×1/8 aluminum flat bar $5.72
- 4″ sq box cover flat blank $.60
- 4″ sq box 2 1/8 dp $2.04
- 3/8 flex combo connector 5/bag $2.70
- #12-2 romex 10ft
10X CP-2199-ND –from digikey.org $17.90Caution: (As of 12/14, None of the plugs currently available from Digikey work in the XO — The molded plastic interferes with adequate insertion.
- Adapter plugs which take 5.5×2.1 and adapt to 5.5×1.7 are available from http://ilovemyxo.wordpress.com/category/how-to-order/
- Also available at http://www.sunsky-online.com/product/default!view.do?subject.id=217872
- And the 5.5×2.1 plugs are readily available in the high volume security camera market — for example http://www.sunsky-online.com/product/default!view.do?subject.id=217872