House battery problem - is it me or Interstate?

Get a meanwell 15 volt power supply. 14.4 is better than 13.6 but 14.8 is better than 14.6, You may need top charges at 15 plus. I have 4 grp 27 that are regularly charged at over 15 v. This is their 8th year in service. My 6 volts always end charge at 15 v. They are a year old and seem to be working good. Some would predict their life to be 6 months.