Did I really get new batteries installed??

[golascart]

I bought a 36V 2002 Club Car DS from someone.
Gave me a receipt dated 2/9/19 that he got 6 CR220 batteries and installed
in the cart. They looked new.
When I went to buy the cart, was clean, ran good, avg speed up his street.
DONE DEAL.
Got home and drove to work (right around the block) but I seemed to lose speed. When I got home I barely made it up my driveway.
So I checked out who could help..
I bought a 36V meter from cartsunlimited
Asked allot of questions about voltages and I was unfortunately told the batteries are bad.
SO ARE THEY???

I checked the battery voltages this morning all above 7.1, but
the meter was only reading 31.
So I disconnected everything and started over.
As I connected each battery I made sure I was getting
around 7V, then 14, then 21.(on my volt meter)
When I finished I connected the 36V meter and ended with 47.7 Volts.

Took the cart for a ride, 36V, drop to 34 on a steady straightaway.
Downhill went to 37+V
Then came back to house and up the driveway. Bottomed out at 32.1
and was barely moving, if 2 people in it, don't think I would of made it.

So, what else can I check the make sure before I go after the seller for bad batteries.