Battery / Charging Tactics In Classes And Clubs

Hello all.  I am reaching out for tips and solutions regarding battery life of EZ robots in classroom situations.

When it comes to double class periods or club events, most robots have issues with battery endurance.  As robots like JD and Roli have their lipos' locked up inside their chassis, a quick battery swap is not possible.

What does a teacher do in this situation, when the battery dies? Do I have to double up on available robots? An exterior battery is not possible as the fuse board and connections to the EZB is still inside (and also is would unbalance a biped)

How are you getting around this challenge?