Making a cheap Chinese voltmeter/ammeter work
Correctly connecting a vDC Chinese volt/ammeter from Ebay
These ultracheap Chinese voltmeter/ammeters can be bought for a few dollars on Ebay. What ultimately arrives in your mailbox a month after purchase is a little meter with no back and two small connectors, one with 2 thin wires and one with 3 fat wires. Of course, no instructions are included.
The problem with having no instructions is that while the voltmeter (small connector) can be connected in PARALLEL, meaning that you can simply hook the red wire to the battery + and the black wire to the battery -, an ammeter must be connected in SERIES, meaning that there must be a "load" between the connector and the battery. If you try to connect an ammeter in parallel like a voltmeter, you will get a nice show of Magic Smoke as your meter commits harakiri.
The thing is, there doesn't seem to be much in the way of ideas online as to how to avoid this ignominous fate. Everybody's got their own idea. This is what I found to work.
I found the idea for a computer fan as a "load" using Google. So I have the meter, fan, and an extension cable that has the same color wires.
The fan is a simple 70mm Raidmax fan.
Meter specs. Note the copper wire-the ammeter shunt. Make sure your meter has a built in shunt!
Everything soldered in place using 18awg solid wire, which is easier to use with the battery terminals.
Makes sure you label your connectors! Or you could use different color wires for each connector.
Circuit diagram
This is my crappy diagram of the circuit. Notice that the yellow wire of the ammeter is connected to the yellow of the fan, with no connection to the battery. The red and black (positive and negative) of the ammeter have connections to the red and black of the fan in the middle of the line from the ammeter to the battery. The voltmeter side can simply be connected directly to the battery.