For many of us, our cell phones are an integral part of our daily lives. They are often our primary source of communication, and with music and video playing capabilities as well as Internet access, they can also double as our away-from-home entertainment. For these reasons, it can be a disaster if you leave home with a cell phone battery that's just about dead. Sure, the battery indicator says it's half-full, but just how much juice does it really have? Here's how to test a cell phone battery with a multimeter so you know for sure.
Turn off your cell phone and open up the battery compartment.
Remove the battery and set it down on a flat surface so the terminals are facing you.
Identify the two terminals on the battery that are labeled with a "+" and a "-" sign. Then, look on the battery's label to find out how much voltage it is rated at. For instance, on the battery pictured, the voltage is rated at 3.7 VDC, or approximately 4 volts DC.
Turn the dial on your digital multimeter so it is set to read DC volts. This is indicated by the letter "V" with both solid and dotted lines above it.
Touch the tip of the red probe to the terminal labeled "+." Keep them in contact while you press the tip of the black probe to the terminal labeled "-."
Check the digital reading on your multimeter to see how much charge the battery has. In this case, the battery has a 4 volt DC charge. It is fully charged.