sounds like you got the problem taken care of.
i take my scooter into my local medical supply store. they have techs that do that sort of thing. doesn't have to be one of their chairs either.
i once changed my batteries only to have them run out several months later.
turned out the batteries were good but the charger was bad and had to be replaced. then i had to buy new batteries

i was really miffed but got the problem fixed.