Performing a Test on a Small-Battery Charger

1 Plug your battery charger into a wall outlet. 

To determine whether or not your battery charger is putting out as much voltage as it’s supposed to, you’ll first need to make sure that there’s electricity running to it. Hook the power cord up to a nearby AC outlet. This will cause the charger to begin channeling electricity, which you’ll measure using a multimeter tool.

• 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 Attach the test probes of your multimeter to their corresponding ports. 

Most multimeters come with a pair of detachable colored probes, one black and one red, that are used to measure the electricity running through the poles of a battery or charger. Insert the end of the black, or negative, probe into the port on the multimeter labelled “COM.” Then, insert the red, or positive, probe into the port labelled “V.”

• 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.

3 Set the multimeter to “DC.”

Locate the dial on the face of the tool indicating the different testing modes. Twist the dial until the pointer enters the “DC” range, stopping on the next-highest setting to the voltage of the charger you'll be measuring. This will prepare the tool to test your battery charger, which supplies DC, or “direct current,” power.

• 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.

Warning: Operating your multimeter on the wrong settings could overload it, or even result in more serious damage such as an explosion. To avoid this, always double-check that it's set for the type of current you're gauging at a voltage higher than that of your device.

4 Touch the black test probe to the negative contact point on the charger. 

If the charger you’re testing hooks up to a battery via a power supply cord, press the tip of the probe against the side of the metal prong at the end of the jack. If you’re testing a receptacle charger like the kind used to reload rechargeable AA batteries, hold the probe to a section of the exposed metal on the side of the charging chamber marked “-”.

Some multimeters have input ports that make it possible to plug certain types of power supply jacks directly into the tool.

5 Hold the red test probe against the charger’s positive contact point. 

Insert the tip of the probe into the barrel at the end of the power supply jack, which is what transmits the live current. To take a reading for a receptacle charger, hold the probe to a section of the exposed metal on the side of the charging chamber marked “+”.

• 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.

6 Check the number displayed on the multimeter’s display screen. 

This number indicates how many volts of DC power the charger is putting out. Your battery charger needs to be supplying at least an equal voltage (preferably higher) to the batteries you’re charging in order to restore them to their full capacity in a timely fashion.

• 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.
• If your battery charger tests well below the recommended output, it may be time to invest in a new one.