Are my batteries really charged?

[Canusa]

I have a 1994 club car. I just got it from a friend. The batteries are basically brand new. 48v cart with Northern Energy batteries. When I got the cart the batteries were completely flat, 0 volts. The charger relay was toast so I fixed it I've managed to get the batteries up to 8.4 volts each and a collective of 50 volts. When I try to drive the cart it struggles to move forward and when put in reverse I need to push it to get it moving but it does move. The charger is acting as it should after even a little use on the cart it goes to 18amps then drops to 2amps for seconds and begins and completes charge, I think.
Any ideas of why the cart is barely moving? Are the brakes stuck maybe? Where do you think I should start? My first post here but it sure is helpful to read some of the old threads. Thanks