Mobile phones have evolved from a luxury that few people enjoyed to the point where many people consider them as an accessory that they use all the time and can't do without. Mobile phone manufacturers are also improving the technological capabilities of the phones with each new release. All this adds up to a large demand on the battery of the phone, and after heavy use they may need to be replaced. You can test your mobile phone battery so that you know if you need to replace it.
Hook your phone up to its charger until the phone indicates that the battery is fully charged. Remove the charger, power off your mobile phone and remove the battery.
Inspect the battery and read the label to see what the battery voltage should be when fully charged. Mobile phone batteries generally have a voltage between 3.4 and 4.5 volts.
Locate the battery contacts. They look like three pieces of exposed metal where the battery makes contact with the phone contacts. Identify the positive and negative contacts. They will be marked by a "+" and a "-" sign, respectively.
Set the multimeter to display voltage. Place the negative lead of the multimeter on the negative contact of the battery, and place the multimeter's positive lead on the positive contact of the battery.
Check the meter for the voltage reading. If the voltage reading of your fully charged battery is .5 volts or less than the voltage on the label, then your battery is probably in need of replacement.
If your battery does not have markings to indicate the positive and negative terminals, you can find them by trial and error. Place the leads on any two of the terminals at a time and look for a positive voltage reading. Once you get this positive reading, you are connected to the positive and negative contacts. A battery that shows as fully charged but then rapidly loses its capacity to power the phone almost certainly needs replacing.