I got a Benjamin Traveler, and use it to fill the guns directly. It runs on 12 volts DC, so you can use it with a car battery. Also can get a separate rectifier that converts 110 AC to 12 volt DC.Has been working just fine. Haven't timed it but it takes about 3-4 minutes to pump up my gun's 480cc bottle from 125 to 250 bar when plugged into 110V.I think the Nomad II and Hatsan Spark are similar, and have the rectifier built into the unit.