I need to use my C600 for 8 or 9 continuous hours in an area that has no power. Judging by the number of postings here regarding battery issues (I have 2 batteries, each of which gives about 10 minutes of usage), I'm wondering if I could use a deep-cycling marine battery and a 12v adapter in place of the laptop batteries. This "area" I refer to is an enclosure that I can drive to, meaning the weight and bulkiness of a marine battery is not an issue.  I considered coupling the marine with a small power inverter, but the inverter would surely drain the marine battery much quicker than the laptop alone.  Any opinions?