Though they can be slightly more expensive initially than regular batteries, rechargeable batteries can often last for years. Determine whether your rechargeable batteries still hold a charge using a voltmeter and battery tester to ensure accurate results.
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Charge your battery or batteries completely using a battery charger specifically made for the type of battery you are testing. Be sure to charge them for the full amount of time necessary. Many battery chargers have a green light that will ignite when the battery is fully charged.
Test the battery with the battery tester to see whether it reads as good or bad. This is the first step in determining whether the battery will hold a charge, but not the most accurate indicator. The battery tester will measure the battery strength before use, but the most accurate way to determine whether the battery will hold the charge it has just received is to use a voltmeter.
Connect the voltmeter to the battery terminals. There will be a negative- and positive-side connector on the battery. The voltmeter should also have negative and positive ends. Connect the positive battery terminal to the positive voltmeter end. Connect the negative battery terminal to the negative voltmeter end. The voltmeter will test the battery strength, but the test should be repeated after the battery has been used a bit.
Place the battery into an electronic device so that it is being drained for a while. Depending on the electronic device, the battery will be drained of its charge at different rates, so the time the battery is used will vary.
Repeat the test with the battery tester and voltmeter after the battery has been used for several hours. If it still has the same charge as before it was initially used, then your rechargeable battery still holds a charge. If not, it needs to be replaced because the energy output is inconsistent and eventually the battery will stop working or become unresponsive to the charger.