When troubleshooting electrical equipment that runs on batteries, the first step towards finding the problem is testing the batteries. Short of taking the battery out of the device and switching it for a new one, testing a battery for good charge is difficult without a multimeter. Hand-held devices, multimeters have probes that test the electrical current coming from whatever device they touch. A quick test with a multimeter is the most efficient way to find whether your battery has a charge.
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Set the multimeter to the Direct Current, or DC, setting.
Set the scale setting on the voltmeter by turning the dial to 12 volts.
Touch the positive probe of the multimeter, marked with a "+" symbol, to the positive probe on the battery, also marked with a "+". Touch the negative probe of the multimeter to the "-" terminal on the battery.
Read the digital screen for the current voltage coming from the battery. If the reading is the same as the original battery rating, found on the side of the battery, it is good. A battery with a reading 20 percent below the original rating should be replaced.