The 21st Century 1BB is a Mobility system that requires a 12V 55Ah AGM replacement battery. The compatible Universal Power Group replacement is the UPG UB12550 12V 55AH (+ on left) Z1 AGM Battery Group 22nf (UB12550), a 12V 55Ah AGM sealed lead-acid battery. This battery delivers up to 660 watts of standby power. It weighs 35.5 lb, uses Z1 terminals, measures 9.06 L x 8.27 H in, and has left polarity. This is a direct drop-in replacement for the 21st Century 1BB requiring no modification to the device.
