House batteries not up to ah rating

Thanks for all the information. I am going out and change the cable configuration as described. Yes, I had the positive and negative on the same battery. My Intelli-power converter charger is supposed to keep the batteries desulfated. But I have a 40amp battery charger and will run thru a few desolation cycles. Also, the converter charger is designed to boost at 14.4 volts and I am only getting 13.9 volts because of line loss.
I just bought the Renogy Solar 100 watt suitcase and can equalize the batteries to 15 volts. I can top off the charge to almost that amount too.