Wish I saw this thread earlier... I fly RC helis with 12s battery configurations (6s in series) and I also use powerlab chargers. My eu2000i has no problem charging 2X5000mah 6s batteries at 4C which is about 40 amps. They're charged in less than 15 minutes too. The eu2000i does not like gas sitting in it. I've found the easiest way to keep carb clean is to drain the float bowl if you're not going to use it for a month or more. The manual explains how to do this with a couple of screwdrivers. Also, make sure your power supply is at least putting out at least 28+ volts. I adjusted mine via a variable resistor in the power supply. Any lower and your genny will cycle in rpm constantly near the end of the charge as the charger will have alternate between boosting and dropping the voltage as its near the max voltage of the battery.