I have a golf cart with six twelve volt batteries wired in series. The system discharges fairly quickly. I have checked one battery and it is OK. Should I check all batteries to see if there is a weak one that is pulling down system.

Absolutely One bad cell could kill another battery in charging and robbing that charge from other cells in all other batteries. I hate to tell you this but ALL batteries need to be matched for charging or very close to each other in levels of charge. Many times people put a new battery in beside a so so battery and kill the new battery quicker because the recharge is mostly going to the much lower battery and eventually the new battery will be dragged down quicker than normal and it become a vicious cycle no pun intended Even if you have six decent batteries that are low and matched these will charge good also and equally get charged and not rob each other on charging

Yes, it is common for in series for the lead battery to be the first to go out. But just one bad one will keep the system from running properly or even operating at all.

Absolutely One bad cell could kill another battery in charging and robbing that charge from other cells in all other batteries. I hate to tell you this but ALL batteries need to be matched for charging or very close to each other in levels of charge. many times people put a new battery in beside a so so battery and kill the new battery quicker because the recharge is mostly going to the much lower battery and eventually the new battery will be dragged down quicker than normal and it become a vicious cycle no pun intended Even if you have six decent batteries that are low and matched these will charge good also and equally get charged and not rob each other on charging

Thank you 21 boat-----I had all the batteries checked, and the lead battery was bad. I replaced it, and the system is working. All of the other batteries were of good order.