Need Help - Cart Won't Charge

[mechanix19]

My cart only recently would only hold a charge for 5 minutes. After inspecting the batteries, there wasn't much water in them. I charged the batteries fully then added distilled water until it was just above the plates. Now when I plug in the charger nothing happens. I checked the diodes, fuse, and replaced the board in my Powerwise charger and still nothing. I tried charging the batteries with a car battery charger and then plugging the cart charger back in and nothing still. Any suggestions on what to do next or where I should go from here? Is there a way I can determine if it's the charger or batteries? Thank for any help.