Thanks everybody for valueable info and suggestions.
Yesterday I bought a DC/AC volt and ampere clamp meter (Uni-T203). and hydrometer to check the gravity. my ups has 5 step of charging, it charges fully discharged battery at 15A, then 12A then 9A then 6A and last stage is 3A when battery is 90% full..
first here are results:
specific gravity of each cell : 1.26 or above
cut off volt : 14.4v
open cell volt : 13.6v ( tested after 10 hours of rest)
Discharge cut off volt : 8.5v
volt on load when fully charged : 12.06 (it drops to 11.99 after 10 minutes of load "450watts" AC:2A or DC:39A). Only this thing is showing some problem, why volts drop so quickly
So heres the result of all tests. after loss of water. what do you think guys.
Thanks and regards.