As a side note...when you charge the
ECV, make sure you turn the charger on. My battery charger at home doesn't have a switch; you plug it in, and it's on. The ECV at WDW lost power because each of the previous three nights when I thought I was charging it, I wasn't....the power switch was off.

That being said, in hindsight I'm amazed I did 3 1/2 days of park touring on one complete charge.