It uses a lot of juice so I'd recommend an auxilliary power source,
Mine seems to use approx 10%-12% of battery capacity per hour on a medium level of brightness with GPS running but no GSM. More than enough endurance for any outbound and return trip for me. I do carry a 7ah sealed lead acid battery as back up power for other devices, and this can also be used to power or charge the Ipad if necessary.