[RMcNeal]

I'd take the batteries and have them load tested. If one was 11.3 while the other was 12.7, it may have a dead cell or cells. Are they wired in parallel and if so, is the positive and negative across both batteries? They should typically charge and discharge together if properly wired. Also, if you do replace, make sure to replace both. You wouldn't want one new one to be killed by one old one.