Running A/C over draws the batteries causing inverter alarm

[captdaveo]

I'm trying to run a rooftop A/C unit that draws 10.5 amps at 120V = 1260 watts.

I have a 2000 watt inverter connected to a 430 amp hour battery bank using 18' of 2/0 stranded cable.

This should be well within the capacity of the inverter, battery bank, and wire size.

However, even with a fully charged battery bank (from 16 100 watt solar panels; batteries showing 13.7V, several days of charging), the batteries drop within seconds to < 11.0V triggering the inverter low voltage alarm.

What am I missing here?

Thanks!!!

[bid_time]

Your AC may run at 10.5 amps, but the compressor likely “starts-up” at much more than that. You possibly don’t have enough “oomph” for a long enough duration to fully start that compressor and get it running; especially if you have any other loads on those batteries at the time of start-up.

[captdaveo]

Thanks for the reply, but that's not the issue. The AC will start and run for a few seconds, so it's getting past the startup load. It's that it won't keep running because the battery voltage drops so low -- even though 430 amp hours should be (in my opinion) plenty sufficient to run the A/C for awhile -- even longer with 40 amps of solar dumping into the batteries at the same time.

[valhalla360]

Are you sure it's starting? A lot of air/con units will start the fan then a few seconds later, start the compressor. Most of the noise you hear is the fan and it's hard to hear the compressor kick on. That would align with it overloading a few seconds after it starts.

Alternatively, did you actually measure the amp draw? If it's actually drawing 12-14amp, that might be stressing the inverter. 2000w rating may be the peak, not continuous rating. Exceeding the continuous rating often has a slow breaker that takes a few seconds before it goes.

[MNtundraRet]

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@captdaveo wrote:

Thanks for the reply, but that's not the issue. The AC will start and run for a few seconds, so it's getting past the startup load. It's that it won't keep running because the battery voltage drops so low -- even though 430 amp hours should be (in my opinion) plenty sufficient to run the A/C for awhile -- even longer with 40 amps of solar dumping into the batteries at the same time.

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The first reply was correct. The fact it quit after a few seconds shows the batteries voltage output dropped to far to keep it running.