OK, The batteries were fully charged already, but I put them on an electronic charger and they showed being full in 10sec. I put them back in the UPS and voltage of 26.50 Vdc with UPS cables connected.
After I plug the UPS to 230Vac, the I hear a couple of clicks and the fan kicks on and battery voltage goes to 27,50 Vdc.
The warning LED is only light on and momentary (or longer) press of either of the two buttons will do nothing.
After I unplug the UPS from 230 Vac, the fan and warning LED stay on for about 10 sec. and then they both turn off. No beeps can be heard at any stage.
Any ideas?
-Jan