Use a digital voltmeter and check the voltage at the battery when you are on shore power. On many converters it will go as high as 14.4 volts and then come down to 13.6 and finally level off to a float or storage voltage of about 13.2
It's probably an old or malfunctioning converter and is staying at too high of a voltage for too long. The battery may be toast and you may toast a new battery if the problem isn't fixed first. As others have said, if there is a converter issue, get a more modern 3 or 4 stage. I wouldn't buy a WFCO converter as they have problems with not going to 14.4 when needed. Some like wfco, I didn't have good luck with the new one that I had and returned it.
