FOBO can be operated either by an external power supply or by its on board lipo battery. A full charge of the battery will power FOBO for over an hour.
FOBO under external power for computer interface.
FOBO under battery power for autonomous operation.
The battery is a 2 cell lipo (Lithium Polymer) battery and must be charged with a special load balancing charger. As with any battery, there is a chance of fire if the battery is mishandled (over charged, shorted, etc). The battery is rated at 7.4 volts (DC), however the actual voltage range will vary from 8.4 volts when fully charged to 6.4 volts when discharged. Things to remember when working with the battery:
BE CAREFUL to not discharge the battery below 6.8 volts as this may result in permanent damage to the battery (it will no longer hold a charge). FOBO has no internal voltage monitor to warn when the voltage is low ... so you'll need to use a volt meter to test the voltage on the battery before usage.
ALWAYS unplug the battery from the power plug in the back of FOBO after usage. Even when the servo power switch is in the off position the battery will still be powering the Arduino board and will drain the battery past safe levels.
When not being used in FOBO the lipo battery can be safely stored in a special fire safe bag.