Battery Tender Plus 021-0128 12V Battery Charger: * Temperature compensated to ensure optimum charge voltage according to ambient temperature * Automatically switches from full charge to float charging mode * Battery Tender at 1.25 amps will charge as fast or faster than any 3-amp charger available * Reverse polarity protection ensures user safety: Red and green lights alternately flash in this condition * Complete 4-step charging program (Initialization, Bulk Charge, Absorption Mode, Float Mode) * 10-year warranty