I am far from an expert but you might want to check a few things first before jumping in to new batteries. They ain't cheap!
Make sure all the tires are up to pressure. Then jack the wheels off the ground and make sure each one rolls freely without undue drag. If both those tests pass then check all your cable connections. A dirty or faulty connection can reduce the power by HUGE amounts and also become a fire risk when really bad. If all your connections are tight and clean and you aren't carrying a tool box or load of firewood around in the cart weighing it down / slowing it down then start checking the batteries. But in all honesty you need to supply more information to get a better answer. 36 volts isn't a lot of voltage to work with.
How old are the batteries? When was the last time you topped off the cells with distilled water? Will the batteries hold a charge over night or for a week? Is it kind of slow all the time but really drags down going up big hills? Does it have stock or oversize tires? What system does it use? IS it OLD with resistor coils or new with a computer box?
Answers to these questions will help one of the guys who know a lot more than I do help you better.
Sorry I couldn't be more help.
Make sure all the tires are up to pressure. Then jack the wheels off the ground and make sure each one rolls freely without undue drag. If both those tests pass then check all your cable connections. A dirty or faulty connection can reduce the power by HUGE amounts and also become a fire risk when really bad. If all your connections are tight and clean and you aren't carrying a tool box or load of firewood around in the cart weighing it down / slowing it down then start checking the batteries. But in all honesty you need to supply more information to get a better answer. 36 volts isn't a lot of voltage to work with.
How old are the batteries? When was the last time you topped off the cells with distilled water? Will the batteries hold a charge over night or for a week? Is it kind of slow all the time but really drags down going up big hills? Does it have stock or oversize tires? What system does it use? IS it OLD with resistor coils or new with a computer box?
Answers to these questions will help one of the guys who know a lot more than I do help you better.
Sorry I couldn't be more help.
I’ve tested batteries and I have 38.4 volts fully charged and have 6.4 volts for each individual battery, and it will hold the charge for weeks, also l jacked up rear of cart to run the wheels and still have no drop of in volts.This is my first cart and not sure where to begin, except to bring it do a golf cart mechanic .
Sounds to me like your batteries are NOT the problem. The volts will only drop a little with an unloaded test like running with the wheels in the air so that doesn't tell much, if anything. How steep are these hills and what kind of weight are you carrying? Most 36 volt carts I've been around only run 11-12 MPH to start with and drop to maybe half that or a little less going up a fair hill. Any idea what year the cart is. Some pictures of the batteries and motor bay might help a little. If you've checked the other things I suggested I'd check and CLEAN each and every major cable connection before I went further. Major cables are any that are larger than 12 gauge. Between the batteries themselves and every large wire / cable it has. I recently had one that was starting to fray a little and knew I need to put a new end on but let it slide awhile let me tell you it was causing a MAJOR loss of power and making a multi meter read incorrectly. There was a world of difference when I fixed that one slightly rough looking cable end! Most golf carts came with 4ga wiring for the motor & controls. That is often right on the edge of being large enough to handle the NORMAL golf course lawns. So if anyone has swapped a smaller cable in somewhere that could also be an issue. Most guys who ask their carts to perform better than stock change the cables to 2ga to let the power flow. Good LUCK!
BIGKID is correct in all he told you 
i would only add to check your motor
take it out (use 2 wrenches on motor cables)
it is heavy !!!
clean the motor with air hose (outside)
check the brushes ... replace if needed
i would only add to check your motor
take it out (use 2 wrenches on motor cables)
it is heavy !!!
clean the motor with air hose (outside)
check the brushes ... replace if needed
