You've just gotten a new phone, but instead of throwing away your old one, you want to store it for emergencies. Before you put it away, you should give some thought to the battery. If you are storing a battery for a cellular phone, it's best to store it empty, or almost empty. Long term storage of the lithium ion batteries that cell phones use can lower the total storage capacity of the battery if it is stored at full charge.
Power on the cell phone with the battery inside.
Leave the cell phone on until the battery drains. This may take several days. You can speed the process by talking on the phone, since cell phones have a shorter talk time than standby time.
Enable wireless services such as Bluetooth or Wi-Fi. Powering these antennas will cause the battery to drain more quickly. Check under "Options," "Bluetooth," or "Network" for these settings.
Turn on an application to make the battery drain faster. If you are trying to drain the battery in a smart phone, playing a movie, music or game will help speed up the loss of charge in the battery since these applications require more battery power to run.
You may want to disable the low battery alarm, so the phone does not disturb you. Look for the alarm settings in the "Options" or "Settings" menu.