One is enough>> Not only does it charge 12V 24V batteries, but it can also be used as a 36V 48V battery charger and even a 60V 72V battery charger. Now you only need one charger to charge different batteries like SLA, AGM, GEL, lithium, LiFePO4, deep cycle battery. It can be used to charge car, motorcycle, vehicle, RV, ATV, SUV, Golf Cart, forklift, Marine, Boat. Two charging modes>> Normal mode and H mode(pulse of high-voltage). Normal mode for daily charging, turn the AMPERE knob to set the charging rate, HIGH for an emergency quick charge. H mode for battery maintenance, LOW rate charging is recommended.