I am going to replace the batteries in my E1. I am not interested in the high cost Lithium or the expensive 6 volt dry batteries. I am considering four 12 volt deep charge marine batteries. I have a source for 810 amp units for about $100 each. I have no worries about reprograming the charger because it went out a few years ago and I replaced it with generic golf cart charger. When I decide to do this, I'll keep you posted on the results.