Surging speed and RPMs on my 2003 CC

[30-A rider]

My 2003 CC 48 volt sereis cart is my first cart and have had it only 4 weeks. Its your average stock cart that does 12 mph or so Im guessing. Recently it seems to have slowed down with its top speed. Today when driving it seems to surge a little with regards to RPM's and speed and I can feel and hear it a little. After narely making it up as paved hill that I usually have no probelms with it and after a mile past this it seemed to drive fastet than when my drive began. I typically plug it in for charging after each ride and my charger is brand new, and shuts off when fully charged.

Additional info is yesterday I had to go back and forth from Nuetral to reverese a few times to back it out of my garage even through the reverse buzzer came on each time. Also when taking off charger today before my drive the low battery light came back on a couple time but once I got going down the road it is gone and hasnt come back on yet.

cart has the original batteries and dated 2004 so Im sure they could be bad but until the past couple of days Ive watched over them keeping filled with distilled just over the lead plates.

Any ideas of my probelm here:

Can this just be dirty connections on the battery cables?
Is this a sign my batteries are about toast?

Any insight is appretiated gentlemen.

Scott