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Test to see if a battery is shot?


dougdrake2

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Hi all - Nothing whatsoever to do with a/v equipment, but I know there are some very knowledgeable folks here, and I don't know who else to ask.

Is there an easy way to see if a rechargeable NiCAD battery is shot, as in shorted out or something? My cordless drill charger got fried the other day, but I don't know which of my two batteries was in it which may have caused it. The only way I thought of testing them (since I couldn't try charging them) was to check for resistance across the + and - terminals of the battery to see if there was a short. One battery gave me about 9.6 ohms and the other gave me 0.6. They are 12v batteries.

Thanks in advance.

Doug

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Doug,

I don't know the answer to the big question. I'd check to see which takes a holds a charge. But obviously you don't want to do that for fear it will harm a new charger.

I would like to point out that using an ohm meter to measure battery resistance is very risky to the meter.

Some years ago I thoughtlessly left a Triplet analog meter on "ohms" and then tried to measure a battery voltage. More than the fuse burned out.

Newer microprocessor based meters have circuit protection which should prevent the distruction of the meter. But it is still a bad idea.

My best guess is to just measure battery voltage, even if almost fully discharged. One with an internal short will probably give zero voltage. A good but discharged battery should show some voltage even if one or two volts. Again, a guess.

You might find a battery specialty store in your area which can help. I found one in the Dallas area which specialized in tool type rechargeables.

I'm a bit cautious because improper charging can cause a battery explosion. I've done that too, as a young lad with a rechargeable toothbrush.

I've noted that unless it is an expensive piece of equipment, a new battery and charger is often getting close in cost to a new drill. But then you've figured this out already. It annoys me that the economics work like this.

This is good excuse to visit Home Depot.

Good luck,

Gil

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Gil - Yeah, you're right. A new drill set isn't that much more. But I found a parts distributor that can get me these parts fairly cheap -- a charger is only $6.50 and I can use the remaining battery I have that IS good. See, if I save money on this, I can spend more on the audio stuff (it all works out, doesn't it?).

Thanks for taking the time to reply.

Doug

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