Battery voltage

[bassfisher]

What is the voltage of a fully charge battery, and does it hurt them to charge them (top them off) even though they are charged? 12.5 to 12.9V

When I charge my batteriers they are charged at 13.7V (I think). Once they are fully charge and I disconnect them they run down to about 12.9V within a few hours (I have no watch that closely), and stay there for a long time. After a few mouths or more, they can run down to 12.7 to as low as 12.2. (Never useing them)

I'm asking this because here of late, when charging my batteriers, they do not charge right. (They never say full.) I have bought a new charger (walley), and still does this sometimes. I have one new TM battery 2 weeks old, the other one, I have no ideal, but it holds a charge for a long time without use, and with use it last me all day for medium use. ( MG TM 67lb thrust 24V , useing it on 1 to 3 speed out of 5, depending on wind, and only use it to move the boat or keep it straight. So no constant use)