Century 4-IN-1 dual range battery charger, booster, and maintainer. 12 volt. Four selectable modes: 2 amp slow/trickle charge for maintaining batteries, 10 amp standard charge, 50 amp emergency boost for jump-starting, and a maintain mode for long-term storage. Analog charge level meter on front panel. Always connect red clamp to positive (+) and black clamp to negative (-) terminal. Do not use boost mode as a substitute for a proper charge — it is for emergency starting only.