1600mAh Lithium Ion battery that can be used with the module. The PiJuice HAT comes with a 1820mAh as standard, so this 1600mAh is a good replacement battery. 

The battery contains short circuit & overcharge protection

Check out the to work out roughly how long your battery will last. 

• Capacity: 1600mAh/5.92Wh
• Volts: 3.7
• Type: Li-ion