How do you know the batts are US?
If they are (take them out and have a real discharge test done on them) then the charging
system needs to be checked. The best way to kill a battery is to abuse it - overcharge or overuse being the most common. It is essential that all the regulators are correctly set for your specific batteries charging
requirements, the alt regulator
, shorepower and solar
regulators etc. Get the manufactures spec sheet for the batts, and check the charging voltages with a quality multimeter, at each charging mode (Bulk, Absorbtion, float on each regulator
, if present) Do NOT take a local service guys word for it that this is done, read the spec sheet yourself and either do the voltage tests yourself or be there and watch while it is done.
The battery computer is not infallible, but any corrosion
or poor connections in its setup, especially at its shunt, and the voltage sense cables
can lead to incorrect readouts. Same with programming the meter/computer.
Remember that the battery computer has programming parameters, including the capacity of the batts and often perkets law parameters for your specific batts. Garbage in, garbage out...
Don't buy anything new until you are absolutely certain you have sorted out any issues, or you will likely have the same problem again!
If this is all too technical, then find a marine
service guy you can trust, perhaps by quizzing him using some of this info?