[Nut-upsuser] CyberPower BR1200ELCD suddenly turns off when BO and specific load is connected.

[Lukasz Michalski]

Hi,

Could UPS be incompatible with the power supplies and devices connected 
to it?

Long story below:

I planned to replace the old Eaton 3S 700 with its four-year-old battery 
with a CyberPower BR1200ELCD because I have specific space constraints, 
and the latter has the biggest battery in this form factor.

The unit is brand new. I connected it to a laptop, configured it with 
NUT 2.8.4, and tested the shutdown and recovery with three other 
connected laptops. I had a 12-15% load during my tests, and the battery 
backup power lasted for about one hour.


Then, I connected it to the final installation, which has several 
different devices: a Mikrotik router (48VDC), a cable modem, a small 
industrial PC (12VDC), and three MeanWell industrial power supplies 
(24VDC). One of the power supplies powers a smart home automation system 
with various Modbus PLCs, I/O modules, VAV actuators, etc., and the two 
other powers two PWM LED dimmers. There is also a 12W, 24VAC transformer 
for an HVAC controller.

The total load is about 10% when the UPS is OL.

I performed the same shutdown test by unplugging the UPS from the power 
line, and it suddenly turned off when the battery charge dropped from 
100% to about 75%.

I charged the UPS back to 85%, and repeated the test with the same 
result. The UPS shut down when the load reached 73%. I turned the UPS 
back on and let it run for a few minutes. It did not shut down the load 
immediately.

In both cases, this was not a NUT-initiated shutdown — the UPS just 
turned off. Another strange thing was that upsc returned a load of 
12-13%, but the display showed 20%. In my laptop tests, the load values 
on the display and in NUT were the same.

I charged it to 100% for 24 hours and sent the battery.test.deep command 
using upsadm. The UPS was OL during this test, which caused the load to 
shut down when the battery charge was about 55%. The test result read by 
NUT was "Done and Warning." I also noticed that when ups is OL, and 
charged to 100% "remaining time" on display switches once per 2 secs 
between two values: 81min and 65min.


At this point, I thought that maybe the brand new battery was faulty, so 
I reverted to the Eaton 3S 700 for the target installation and performed 
two tests:

The same discharge test when target installation was on Eaton - no 
problem, Eaton lasted for 20min and properly shut down at 20% state of 
charge.
I've connected 4 laptops to CyberPower to simulate the same load that I 
saw on display (~20%). No problem - CybePower lasted for ~1h and 
shutdown properly.


Has anyone had a similar problem? What could be the cause?

Thanks,
Łukasz