NEC MOBILEPRO 900 - Manual (Page 106)

A-6 Troubleshooting
Replacing the Backup Battery
The MobilePro uses a CR2032 lithium coin-cell battery to maintain
system configuration information. If the battery fails to maintain
system configuration information, replace it with an identically rated
battery from the same manufacturer.
The battery can explode if you use a battery
that is not the same type battery (or an equivalent type) that ships with
the MobilePro. Use only the same type battery or an equivalent type
when replacing the battery.
Lithium acts as a catalyst when exposed to water and causes
spontaneous combustion on contact.
If you need to replace the battery, follow these steps.
1. Save your data, turn off unit power, and close the display panel.
Disconnect any cables attached to the unit, such as the PC Connect
cable.
2. Locate the backup battery cover on the bottom of the unit.
3. Using a coin (for example, a quarter), loosen the backup battery
screw and remove the cover.
Locating the backup battery cover and screw
A – Screw B – Backup Battery Cover