A good way to check your batteries is with a hydrometer. Ace sells a good one here:
http://www.acehardware.com/product/i...ductId=1292142
A dealer will run a discharge test. A bad battery will show signs of failure during this test. Google around for discharge test.
When you say you are getting the correct voltage, you mean the pack or individual batteries? What are the voltages after charging of each battery and letting the cart sit for 6+ hours?
As far as the EZGO sales, when I was told 4-12V batteries would go 60 miles I laughed out loud, the guy then claimed his Mom got 73 miles. I said the AC motor must be really efficient! IMO, the problem is that people run their batteries down to a state of charge less than 80% way too often. In addition they do not break the batteries in properly. I doubt the dealer does this and we get our cart and off we go. You should "never" run your pack to less than 50% of charge. Over time this will really affect the life of the pack.
As an example I know my CC rebuilt to handle 8-6V batteries will go 60 miles, possibly more. The reality is that is it is at 50% of charge at 45'ish miles. I would "never" run it down more than that. I do not know off hand the amp hours for 4-12V batteries or how far you should drive to discharge less than 50% (MAX).
As I have always said I love the performance of the EZGO, but I really hated the fact they could not have designed it to take 6-8v or 8-6v.
I have to run before my thoughts are complete, but I always wondered how they could put adds in the paper for 60 miles. Maybe this is a tack the group could take against the company.
BTW, do they all have 48-12V reducers in them for accessories?
good luck, hope My ramblings made any sense,I am in a hurry.