Fully automatic high frequency charging delivers 3 stage charging, automatically switching from fast charge, to top-off, to trickle charge. Battery reconditioning feature helps extend battery life; 40 amp engine start helps start your vehicle in about 90 seconds. Equipped with reverse polarity protection; LCD screen displays charging status and battery status with easy to understand icons. Features a patented alternator check which indicates if the alternator is maintaining battery level; ETL Certified for performance and safety