How to Test AA Batteries With a Voltmeter

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Testing batteries with a voltmeter is quick and easy. The test can tell you if the problem is with the battery or with the device, provided you know how to test batteries with a multimeter or voltmeter. The important things to keep in mind are making a good connection, reading the right scale and what it is exactly you are looking for.

Standard Voltage of an AA Battery

Consider how much power the device needs to function. AA batteries are supposed to deliver 1.5 volts. When fresh they usually deliver slightly more than this and they continuously degenerate. Every manufacturer has an online page describing the characteristics of their batteries, and this is usually the best place to check for specific information regarding your battery. Typically, manufacturers consider AA batteries spent when the voltage reaches 0.75 volts, but this may vary.

Set Your AA Battery Tester to DC

Set your meter to DC to measure batteries. Voltmeters measure both AC (alternating current) and DC (direct current), and multimeters do this in addition to measuring current and resistance. If you have a multimeter, you just need to choose the DC voltage mode, usually by turning a dial on the front of the device to the appropriate position.

Once you have it calibrated for voltage, you need to choose the smallest scale that is larger than 1.5. If the scale steps are ×2, set your meter to 2V – this will work out fine. If the steps are ×10, set your scale to 10V – this is going to be harder to read, especially if you have an analog meter (with a needle instead of digital readouts). Make sure the leads are plugged into the meter correctly – red to positive and black to negative.

Connect Your Meter to Your AA Battery

Hold the test leads to the ends of the battery. The red leads goes to the end marked positive, and the black lead goes to the negative terminal. The battery terminals are usually marked, but if they are not, the terminal that has a protrusion is positive and the terminal that is flat is negative. Move the leads around a little without losing contact with the battery. The highest reading you get is the correct one.

Read Your AA Battery Voltage

Read the meter. If it shows 0.75 volts or lower, the battery is probably worthless. If it is around 1.5 volts, the device it came out of might need repairing or replacing. If the reading is near one volt you might have a battery that will not work for this device but is not completely worthless. Try a new battery in the device and if that doesn't work the device is the problem. Save weak batteries for emergency use in other devices, Smoke detectors can usually function with weak batteries and they will tell you loudly if the battery is too weak.