UPS not charging on electricity but charge on Generator

Thread Starter


Joined Nov 23, 2015
Good day everyone,

Please my office 30KVA UPS will not charge on main supply (electricity). It only charge while on generator (plant).

The batteries are not up to a year.

Please what do you think is the issue.



Joined Oct 15, 2009
Need wiring diagram showing how generator and mains are attached to UPS..
Need to know UPS specifications
Need to know voltage measurements for mains and generator output
How do you know its not charging?

As alfacliff stated an electrician should be able to look at it and find out whats wrong easily.


Joined Oct 29, 2013
Is this a problem that suddenly began when the system was working properly in the past? Did anything change just prior to this problem occurring?

Check your utility line voltage. We had a problem with the line outside our building causing the voltage to sag, and our UPS's were running in boost mode (drawing more current to boost the voltage). Occasionally the voltage would drop low enough that they would trip to battery power, but they would run for extended time in this boost mode. I believe the batteries were not charging when running in this state. It's worth checking if yours is similar. Check the line voltage, and also check the UPS logs is possible, the UPS will likely log the events.