My Experience with Inverex VM 3.2kw UPS

I bought an Inverex vm 3.2kw ups with two AGS Batteries in august 2018. After installation, UPS started working successfully. After using 11 months, I decided to install Solar panels, so I bought 8 Mono Solar panels (Inver-perfect from Inverex) of 300Watt each in July 2019, and I installed them in series and parallel array as mentioned in the manual of UPS. Its max open ckt voltage is 102V while the working voltage is 30 to 80 V. So I connect two solar panels in series and 4 in the parallel array(total 8). however, in the first instance, I installed only 4 panels in the same arrangement (total 1200 watts).

Problems Faced in UPS

Even after using the load of 1000watt solar power does not exceed 500watt, and the maximum PV current UPS LCD shows 21Amp. Remaining power it consumes from the battery. The maximum solar current was not exceeding 7.3 Amps. I was surprised that on 1200 watts, ups only operate on 500 watts. Then I attached two more plates, and now the solar wattage becomes 1800 watt, but UPS has the same situation of not exceeding 500watt(it was jumping to 543watt max). I again attached two more plates (as I bought 8 solar panels), so the solar power now becomes 2400 watts, but again UPS is unable to handle power of more than 500 watts.

On High Load

Tests

I have done a short circuit test on each solar panel and found about 9Amp current. All the panels were ok. Then I set all the parameters of UPS (i.e Solar first, Solar only, Charging current to max), but nothing happened, only 500watts.

On Low Power

Observations

After observation of 15 days, I finally found its solution. I have seen that in the morning time, the UPS was giving full power, then I observed that when voltage is below ~71 V the UPS was working at full throttle and when sunlight increases the voltage also increases and reached to 82V, then UPS stops at 500watt. Even after putting a heavy load of 1200 watt voltage remains at about 77V and the solar current does not exceed 7.1 A.

Final Working solution

There was no other solution in the series combination of solar, so I installed all the panels in parallel(6 panels as the maximum current of Solar charger UPS is 50Amp), now the total open circuit voltage is 43V, and the current of 48Amp. Now the UPS is working absolutely fine max current of 46Amp was observed with the DC clamp meter, and on load, the solar voltage drops from 34V to 31V and solar max power was observed 1.28 kw on UPS LCD.

Suggestion

If you attach 2 x 250-watt solar panels in series with 3 arrays, then this may work b/c the voltage of 250watt solar panels is a little bit lower than that of 300 watts. and the maximum solar charging current is 50 amp, so on a 24v system, the maximum power UPS can handle is 1200watt. however, I have installed 1800 watts of solar panels, and the maximum power observed is 1280 watts on UPS LCD.

1.28kw

1.27kw

Solar current