Bad quality batteries.

Similar to a number of other reviewers, I have been very disappointed with the omnipower 12V Gel batteries from Sinetech. I purchased a set of 4 120Ah batteries to feed a good quality 48V inverter. They were only cycling during loadshedding (no PV pabels in my system). Initially the system would provide 6 hours of backup. However within 10 months (about 30 cycles max) the batteries were only able to last 1.5 hours. I made a warrentee claim with Sinetech, and after having to prove that i did not abuse the batteries they eventually replaced them, for which I was thankful. I also adjusted the inverter settings according to their recommendation. Now after 8 months the new batteries are again at very poor capacity. There is nothing wrong with my inverter, there is something wrong with these omnipower batteries.