playing with Batteries, in a lightly modified version of Mehdi's original code
aha, the batteries are serving as a 'trash can' for excess power. the MILP fails if the generator output (100,000W) can't be packed into a combination of loads and battery.
added plot of battery charge level
adding extra decision vars for battery overflow
saving a version that uses naive 'infinite battery'
having trouble with ~(Overflow>0) and ~isOverflow