To the OP - may I suggest swinging by BeechTalk.com. There is an 'other brands' section on those forums and you'll fund great advice and discussion (with real names) over there.
As the -42 is shared between a number of airframes, there's lots of great experience on it.
Personally, I think your battery is a little weak. -42 equipped King Air with a Hawker 40Ah battery I usually see 16-17% NG before it starts to stabilize.