This might be TMI too late but I run my V3 for 9-10 hours on one battery charge wich really helps at festivals like Bonnarroo.
I use a 6V - 12 Ah WKA6-12F Batt. (from Batteries Plus). I have at least two and keep one on the Werker WK6V1000 charger. I'm attching a data plot showing the Batt. on an actual unit. The dip in the data at hour 11 is where the V3 auto shut-off kicked in. Time will vary with temp. and batt. conditions.
Hope this helps someone. Now if I could just find a way to power the Korg MR1000 without going trhough so many AA Batt.
- Dany