Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!
Batteries are not being charged! The 8 volt battery should be over 8,5 volts when fully charged. Use voltmeter to test charger output to batteries, check the voltage at battery pack, before attaching charger, then plug in the charger and watch the voltmeter, voltage should start out pack voltage and slowly increase as batteries are charged, and charger should run about 8 hours for full charge. With club Car, you may need to reset the OBC, which controls the charger function. Here is link.
Motor brushes would affect performance, but you have a battery voltage problem, as 48 volt pack fully charged will be over 54 volts!
There is a way to bypass the OBC, bit then charger has to be unplugged, or it may keep charging. See one below.