I got this pretty much as a lark. I thought it might help me find Ni-Cd cells that were taking on a fake charge.
It's an 'AMPROBE'[1] BAT-200 Battery Tester.
For $5.99 CDN I figured it might at least be cheap entertainment for a while.
There's not much to it; here are two views of its innards.
There's a meter, and a tiny printed circuit assembly with four resistors on it. I tried it out on a variety of cells and 9V batteries, and I decided that it's not a bad little instrument; it's quite well thought out.
There's a chart on the back of it that makes it pretty clear what the unit is up to.
For 1.5V cells, the tester puts a 4 ohm load across the cell and reads out cell terminal voltage under that load. (375mA nominal.) A terminal voltage above 1.0V is a 'good' indication; a terminal voltage below 0.9V is a 'bad' indication. Similarly, for 9V batteries, the tester puts a 215 ohm load across the battery and reads out battery terminal voltage under that load. (42mA nominal.) A terminal voltage above 6.5V is a 'good' indication; a terminal voltage below 5.3V is a 'bad' indication.
Those test loads are reasonable, and they give a reasonable indication of cell/battery condition.
So, the item is not a gimmick. It really is what it says it is.
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NOTE:
[1] The Chinese manufacturer is doing a shameless bit of brand name piracy there. Amprobe is an American manufacturer of high-end electrical instruments. There's no way that this little tester is an Amprobe product.
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