Combines Batteries or alternatorIJ

Definitely alternator. If it was O.K. the system would run at about 13.5 volts until you shut down, regardless of battery condition. Did it crank up O.K. at startIJ

Thanks for the reply. The alternator is still under warrenty so I'm replacing it. Need to get started on fescue seed. Been getting a truck load every day which is about $1200.00 for my half. So we have to get it while it's there. Thanks for your help.

low voltage kills components friend. Try not to let this problem go too long. Voltage when batteries are charged and engine running should be 12.8 to 13.2, when they are low and engine running it can be as high as 14.8. It stays at 14.8 continually you have a battery problem. I would charge the batteries over night if possible as soon as you can and then load test them. The first thing to go will be the starter from low voltage. Some times bad grounds and even bad hot leads that are loose or corroded can cause good voltage signal at the alternater but the juice never makes it to the batteries.