BK650 quickly off and on just once when startup

[BillP]

Hi ,

I am using BK650-CH,

I manually shutdown the ups and then turn it on, just several seconds after, the ups quickly turned off , after about 1-2 seconds it turned on again, I can hear the clicking sound while the quick off and on, everything seems to be OK after that.

I have tried process above twice yesterday, always the same result,  Is there anyone knows what is the cause of that ?

Thanks in advance!!!