You need to wait and take measurements before once charging stops, one way of doing so is that once batteries are fully charged, then put it into the backup mode for 10-15 seconds by switching off the input from wapda and then measure the voltage at battery terminals before charging stops again maybe within minute or two after.
Every measurement has to be taken on some index which here is once charging is about to stop, once UPS TRIPS (low cut off voltage), charging rate, AMP-HR rating of your batteries, calculating maximum allowable charging rate for individual case, specific gravity readings once batteries are in fully charged state, readings other than that will only confuse you.
It is normal 13.5Volts, if you will wait then this will go up till it reaches 14.0-14.4 between which you have adjusted the cutoff voltage, that is what you have to see, if its properly adjusted or not.