Button batteries are small batteries that are usually used to power small electronic devices. They get their name because they are round and resemble buttons or coins. Many people are unfamiliar with this relatively new type of battery. If you have an electronic device that has stopped working, it may be a simple matter of a dead or dying button battery. There is a testing method for button batteries that will allow you to check their condition.
Remove the battery from the device and inspect it to determine the battery voltage. The voltage will be marked on the battery. Most button batteries are between 1.35 and 3 volts.
Set the multimeter so that it displays voltage on the DCV scale.
Determine the positive side of the battery by finding the side with a "+" marked on it. Touch the positive probe (red) of the multimeter anywhere on this side.
Touch the negative probe (black) of the multimeter to the negative side of the battery, which is of course the opposite side from the positive side.
Take note of the displayed voltage on the multimeter. If it is 10 percent (or more) less than the marked voltage on the battery, replace the battery as recommended on BobVila.com. For example, a 1.5 volt battery should show a voltage of at least 1.35 volts, and a 3 volt battery should show a voltage of at least 2.7 volts.