The current battery_t uses the timestep variable dt_hr as a fixed parameter that cannot change within a simulation.

Allow the battery_t timestep to be changed from the interface, and make sure all the component models are updated with the new timestep.

Alternatives are to construct a new battery with the same state and parameters save dt_hr. This will be more computationally inefficient.

This is required for the battery model to be used inside EnergyPlus' power & heat convergence loops which use adaptive timesteps.