Chamberlain. The maker’s EverCharge Standby Power System offers a reliable way to ensure garage door security, safety, and convenience during a power outage. When power is lost to the home, the EverCharge Standby Power System automatically takes over garage door operation. The system supplies power for up to two days, and will still perform 20 full up and down cycles after 24 hours of standby time. The system operates as if the power were still on, so all remote controls and opener safety systems, such as reversing sensors, work normally. EverCharge Standby Power System comes standard on Chamberlain’s LiftMaster 3850 opener, shown. 800.528.6563.