What stands out Add more power to your doorbell & enjoy up to nine months between charges with this extra battery Charge within the doorbell via micro USB (Universal Serial Bus) or in a battery charger It takes seconds to swap the battery in your doorbell so there’s no need to go without Compatible with the electri Q Wi-Fi doorbell (ei Q-SMVDBL) The details Extend the battery life of your electri Q Wi-Fi doorbell with this useful addition. Adding up to an extra three months there’s really no need to worry about your doorbell quickly running out of power. Also ideal as spares you can replace the set in your doorbell & never be without power. The batteries can easily be charged in the doorbell via micro USB (Universal Serial Bus) or in a battery charger (not included) Essential info. Charging method. Micro USB (Universal Serial Bus) via doorbell / battery charger Battery type. Lithium ion Compatible with. ei Q-SMVDBL Wi-Fi doorbell.