Hi Larry,
It sounds like you are going to go to the south rim. This info is a little dated (1.5 years old) but, the RV parking grounds have a few 50A hookups set aside for EVs, it was 4 hours free, ~$10 or $20 for longer. We simply payed for the spot (the 10 or 20) and camped with our car there. The location is on plugshare and it sounds like things may have changed with new ownership in last few months so I'd check what the deal is now.
Peter