Input voltage shouldn't affect output voltage on a charger. Unless input drops and the charger starts screaming like a raped banshee. The first thing that comes to mind is where you were running it. On pavement and probably high speed runs. Lots of current draw. And that is some serious motor for 2wd. Never-the-less, I've used the Carbon 3200 for over a year, on-road and off. Everything from stock to full blown mod, and never had any problems except that time I plugged it in backwards in my sedan. Half a battery bar and a friend with HUGE balls took care of that.