House battery problem - is it me or Interstate?

I run a 150w 8.5 amp solar panel and 15.0V to my battery, a 150Amp hour 12V golf cart battery. My Specific gravity stays up, where it belongs.

YMMV, I am not afraid at all to top charge my battery and get it full, like it belongs, so it doesn't sulfate the cells.

You need higher voltage to do this. whether it's 14.4 14.8 or 15.0V, only you can determine what is enough by taking a specific gravity reading of each cell on each battery after fully charging. 1.275 or higher is what you need at 72F.