I tried the Duracell NiMH. They are white casing and rated at 8.4V. After a fresh charge they clocked in at 10.41V. The mini did not like this battery. Perhaps when it hit ~10 bps it would vent and need to be reset. Easily reproducable when you put the mode to ramping. No chops, just venting. Changing the battery back to an alkaline Duracell allowed the mini to function flawlessly again.