All I know is that when I am running a Benedini ,15 watt amp with a 12 volt power convertor the brown out with NiMH is almost inevitable if the tank gets into some heavy lifting. With Lipo's there is no issue. Maybe if a guy went back to a receiver batter pack might help as well and isolate your electronics from the mechanical side of things. .
Oh I see, Dan
You use a 12 power inverter, I bet that's the issue with your battery browning.
From my experience building power supplies, the current draw can be excessive (and instantaneous) to maintain voltage level on the output. The recovery of battery is typically too slow for most inverters when drawing surge current from my experience.