Hello everybody, long time reader.
I've read whole 6 threads about DR680. I'm also owner MK I for a year now. I did a capicator mod myself and i must say i can see a difference.
Also about battery power i build a power supply myself. Can say that its checked for more than a 6 months of use and its very good and stable. No problem with overheating and its very efficent.
I used LI-PO battery 11,1 V 25C 10000 mAh (like this one:
http://www.ebay.com/itm/10000mAh-11-1V-ZOP-25C-Li-poly-Lipo-Battery-For-Car-Boat-RC-Airplane-Plane-/271587643995) connected to power stabilizer/converter (
http://botland.com.pl/przetwornice-step-up-step-down/2127-przetwornica-regulowana-step-upstep-down-s18v20alv-4-12v-2a.html). This converter is essetnial: you can put any DC voltage from range 2,9 V ti 32 V and you can set (useing multimeter) a desire output voltage in a range between 4V to 12V, and its also giveing max 2A power on the end. I know that its 500mA less that's on the AC power adapter, buts by my test its a bit more thats realy needed - checekd on working unit, all 3 phantoms ON and recording.
This battery give me about 7-8h of recording at least. Never used all. Also there is one more thing thats good with that stabilizer. If the battery is fresh after charge it will give you a bit more (still less than 12V, but in case of other kind of battery - perhaps higher voltage - it will drop the voltage down to 12V). With time when the battery discharge the voltage will drop, so the converter will upscale the voltage to 12V - cost of capicty of the battery. If the converter will not able to scale the voltage more, and the output voltage will drop more than 1V it will cut off the circut - so the unit will switch to internal battery.
Edit: Also the good idea is to add LiPo Buzzer, not to destroy battery cell with overdischarging.
Hope that helps.