I think the idea would be to leave the battery at the field with its solar recharger. It would be constantly recharging between flying sessions and ready to supply at least a few hours of recharging capacity. A deep-cycle battery would be the best bet. It ought to be easy to tweek solar recharge and battery capacity to suit an individual's flying requirements. Also, you would need to be confident that the battery and recharger would be secure at the flying field during flight sessions.