Kastar super high capacity battery will power your doorbell for much longer; Easy to charge with the Micro-USB cable. Battery Type: Lithium-ion; Battery Voltage: 3.7V; Battery Capacity: 7000mAh 25.9Wh. Safe to Use: Kastar lithium-ion battery cells meets UL1642 & CE safety standards to ensure that your battery pack will be safe to use as a replacement for your unit. Comes with built-in over-charge, over-discharge, over-voltage, over-current, and over-heating protection circuit. Save Money & Time: Do not spend too much time and money on frequent brands with low quality replacement. With our longer run time & protection features, your cycle life will also be improved because you get quality product for your doorbell.