The Model 3324QC-105 amp GPU is designed for ground use to perform both engine starting and maintenance functions. This model can be used on the ramp to conduct engine starting and will provide 28.5V of continuous clean no duty cycle power when plugged into 220V AC wall power. To recharge the unit, simply plug it into an AC wall power outlet and leave it plugged in when not in use. The high tech proprietary chargers will maintain 100 percent battery charge without over charging the batteries.