Just wanted to post a warning, at least for anyone using a Hyperion EOS0720i Net 3 charger but it probably holds true for most lipo chargers.
If you are at the field charging lipos, don't run your car engine at the same time as you are charging. I ruined my charger by doing this. First it was operating strangely, over charging the lipos. Then when I turned the car engine off it seem to go back to normal but not for long. Now it give a high voltage output warning and won't charge. It also blows fuses if I try to use it from the ciggarett lighter plug (with the engine off). So I fried something on the inside of the charger!
Learn from my mistake!
Fortunately I have two Hyperion chargers one D/C (that I ruined) and one A/C D/C that I'll be using from now on.
Now if my car battery gets low (charger shows low voltage input) I'll disconnect my lipo charger from the car battery and run the car for a while to top off the car battery....then turn my engine off and start charging again.