Rechargeable lithium-ion battery for FlowZone® sprayers. This durable battery pack is rated for up to 1,000 charge cycles. Spray continuously for over 3 hours with 3X protection battery technology so that you never have to worry about: 1. Overheating - cuts current if temperature becomes too hot 2. Over charging - will stop charging at 100% charge level 3. Voltage protection - will not accept higher amperage input Never be surprised by a dead battery thanks to the LED indicator lights on the front of the battery. Pressing on the battery icon will show the charge left on your battery and the lights will blink as the battery is charging. *NOTE* Only charge using the 21V/2.5A Quick-Charger (Part #: FZAAEL)