Batteries and Multimeters

Old 12-17-10, 04:33 PM
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Batteries and Multimeters

I've tested several batteries (standard AA etc, rechargeable, and computer motherboard ones) recently that have given odd readings with my multimeter, and I don't know how to interpret them. Rather than show a fixed voltage, the meter jumps to one reading and then the dial drops down at a moderate speed to another value (usually 0V), or else slows down dramatically around a particular voltage and then continues to drop from there at a very slow rate. In each case the battery is ultimately declared dead, but I'd still really like to know what's gong on.

My multimeter is analog and looks similar to this one.
Old 12-17-10, 06:10 PM
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It is not unusual for a battery to "come back" to near its normal voltage when left disconnected for a short time. When you connect the voltmeter the battery is now "under load" and a bad battery will do exactly as you detailed. For best testing you really should use a battery tester that applies a significant load (for the suspect battery) such as this one.
Battery tester They're readily available from numerous sources, many local, and cost less than $5.00.
Old 12-17-10, 06:39 PM
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A 1/2 watt resistor does the same thing.

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