The mains supply in my area goes out very frequently, I am using two new liquid lead acid batteries (12V-130AH) with my above UPS. If batteries are half drained & I connect mains to charge the batteries, it starts charging with very low current i.e. 3 Amp & keeps the same charging rate through out. This do not build up the charge quickly to provide backup during next power failure interval. I also found out that if ups is charging for 3 hours or more the battery voltage reaches at 27.24V & it stars trickling to maintain the charge at 27.24, I guess it is set for 27.24v. How I can increase this charging/cut off limit. pls. guide