Use a multimeter to determine if a rechargeable battery still has enough voltage to hold a charge.
Q The battery on my cordless drill runs down quickly. Can you help me solve this problem? The battery is 14.4 volts.
Alva Cahill, via e-mail
A Chances are your battery is worn out or damaged. To test it, first plug it in and charge it for at least an hour. Then set a multimeter to a 24-volt range setting and touch the two battery terminals with the probes as shown. Fully charged, a battery should test 1 to 2 volts higher than the voltage listed on the battery. In your case, the battery should show at least 14.4 volts and maybe even more than 15 volts. If it’s below 13 volts, the battery needs to be replaced.
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The main reason that power tool batteries go bad is they’re run down too low before recharging. This can cause a polarity reversal in some cells, which is why they fail to reach their listed voltage when recharged. Unlike cell phone batteries, a power tool battery should be charged as soon as it begins to slow. Let it cool, then put it in the charger at room temperature. A battery may also fail if it sits for several months and the power drains completely.
Sometimes a battery dealer can replace the cells in the battery. But that’s usually not worth the cost if you can find replacements. Unfortunately, replacement batteries for inexpensive power tools may be hard to find, and their life span is often relatively short.
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If your battery shows a high voltage but still doesn’t hold a charge, take it to a tool repair shop for additional testing. If the battery tests OK, the problem may be in the way you use the drill. If you overburden the motor by using a dull drill bit or pushing too hard when drilling, you’ll quickly drain the battery and strain the motor.
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