Features:
For Lithium battery expansion board:
Battery capacity: 3800mAh Maximum
output current: 1.8A
Output voltage: 5.1V ± 0.1V
Double USB output;
Standard charging current / voltage: 1.0A/5.0V
It can last about 9 hours if only pi 3.
The Lithium battery expansion board can be also used on cellphone.
Note: You can charge this battery even if the switch is turned off