The attached picture shows the watt meter I cobbled up this winter from parts and two meters I have.
The small black coil is a 1 milli-ohm shunt made of 14 gage (AWG) house wire. The 1 ft. piece of wire shown in the picture cost $0.19. I had all the conectors and the two meters so my total cost ws $0.19. The meters are typically available for $10 each or less. To make the 1 milli-ohm shunt use a 7 1/4" piece of the 14 gage wire. Alllow an additional 1/4" on each end for the solder connections. I rolled the wire into a coil but first folding it in half then winding it makes it non-inductive. The shunt produces an output voltage of 1 mv per ampere so with the meter on the 200 mv scale it reads amps directly. The second meter reads the voltage between the battery plug contacts. It will handle at least 30 amps continuously and probably 50 or more for a short time. Not as elegant as a real watt meter but definately less expensive.
Topic: A do-it-yourself Watt Meter (Read 443 times)
