The original post started on July 29th. Doubt if he is still making a decision.The original Sondors in 2015 didn't have an LCD, and is a one speed. In general, the later model with an LCD and a 7 speed derailleur is preferred. Ask the seller what kind of range he gets now, and whether he pedals it. I think $350 isn't a bad price if it's a newer one. The older one ...maybe $300. It had to have been a heavy bike to move wih only one gear.
Light use iis like taking it down to half charge on pedal assist. Heavy use is run the bike on throttle til it stops. The latter shortens lifetime. The former is pretty easy on a battery. I've got a battery from 2015 (not a sondors bike) and it saw light usage. Still at 90% of its original capacity.