I have two deep cycle batteries that are being used to power a 24 volt Minn
Kota trolling motor.

This spring I replaced one battery which was not able to read higher than
10.40 after charging.

The new battery is happy and reading 12.75.

The old remaining battery reads 12.70 immediately after charging, but seems
to drain down to 12.20. I have been reading on calcification and think that
this battery is starting to loose its ability top hold a charge.

The combined batteries is reading 25.25 volts now.

My question is - do I need to replace the old battery that is not able to
stay above 12.20 or will this combination work? Also, is there anything that
I can do to "pump up" the old battery.

Thanks for the help.