Brief Description: Test battery pack (variable polarity)
As planned, I made a stop at Batteries Plus and Radio Shack this morning to pick up the items to fabricate a 12v power pack for testing various electrical components and circuitry. I had originally planned to purchase a sealed rechargeable battery (12v) but decided to substitute two 6v lantern batteries instead. The lantern batteries were a bit less than $4 each versus the $52 price tag for the rechargeable alternative (battery plus a charger).
I began by building a simple box from scrap particle board with a top constructed of 1/4" project plywood (birch). The box was made just big enough to hold the two batteries and a small compartment at the end for a DPDT automotive switch and a few wires. The batteries were wired in series to get 12v and then connected to the DPDT switch. The switch was configured so the polarity can be changed by simply toggling (on(+)-off-on(-)). The two leads coming from the switch output are terminated with alligator clips. I used 18 gage stranded copper wire for the whole project.
I finished up by painting the battery box black and staining the top. After the paint and stain dries, I will apply one or two coats of polyurethane, add a carrying handle, and four small nylon feet to the bottom of the box. This little power pack should be perfect for testing items like trim servos which require polarity reversal to move the jack screws in opposing directions. It should also be handy for testing circuitry.
