If your battery charger has a separate On/Off switch, go ahead and flip it to the “On” position. A multimeter, also sometimes known as a “voltmeter,” is a type of instrument designed to test the power levels of various electrical devices. You can pick up a digital multimeter from any hardware shop or electronics supply store for as little as $10-20. [2] X Research source
In some cases, the test probe ports may be color-coded rather than labelled, depending on the design of the specific model you’re using. If your multimeter features built-in test probes, you can skip this step.
To test a standard AA battery, which is about 1. 5 volts, you would use the “2 DCV” setting. “Direct current” means that the electricity runs straight from the device generating it to the device receiving it. [4] X Research source
Some multimeters have input ports that make it possible to plug certain types of power supply jacks directly into the tool.
If you accidentally get your poles mixed up, the multimeter may display a negative reading (or no reading at all). Switch the position of the probes and try again.
If you’re not sure exactly how much, consult to the instruction booklet included with your battery charger, or look for the information somewhere on the charger itself. For reference, a standard lithium ion battery is rated for around 4 volts of electricity. Larger devices and appliances may run on batteries or battery packs that put out 12-24 volts. [8] X Research source If your battery charger tests well below the recommended output, it may be time to invest in a new one.
If you like, you can also turn on your vehicle’s radio, fan, emergency flashers, and other electrical components to load the battery even more. [10] X Research source Eliminating surface charge helps to ensure a reading that accurately reflects the alternator’s charging capabilities.
Car batteries typically put out 12 volts of electricity, which is about 6 times more than most personal use batteries. To avoid overloading your multimeter, make sure you have it set to a voltage higher than that of your battery (20 DCV on most tools). [12] X Research source
Immediately after attaching both probes, your multimeter should display a reading somewhere in the range of 12. 6 volts. This is the battery’s static voltage, which only shows that it’s holding a charge, not that it’s charging the way it’s supposed to. [14] X Research source
If your headlights or other electrical components dim or cut out momentarily when you start up the engine, it could be a sign that your battery is going bad.
If there’s no change in the reading, a failing alternator could be to blame. Consider making an appointment to have your vehicle looked at by a professional. [18] X Research source Look for a reading within the same range if you’re testing an external battery charger.
