I've reserved a USE 6 pack for my handle bars. It'll hopefully get me 15 hours. I've various back up lights which I'll bring, for my helmet mount.
There is a 'camper battery' in the campervan which is separate to the engine battery, so we can charge off that. I believe USE will swap the rented lights for a charged set.
To reserve a USE set you can ring or email them and they'll out you on the list.