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Bruce Orr avatar image
Bruce Orr asked

5.5kw Generator slowly drains batteries

I have a 50amp RV with 2 Quattros configured in split phase. The generator supplies power from 2 30 amp (in phase) breakers. From the generator, I connected the red wire and neutral to the master Quattro L1 as AC In1. I connected the black wire and neutral to the other Quattro L2 as AC In 1. AC In 2 is my 50a shore power. My shore power works great and both legs meet the loads and charge the batteries.

But when only the generator is running, only the loads of L1 and a very small amount (if any) charge the batteries. The Cerbo shows 0 watts of generator power to L2. As a result, all L2 loads are inverted from the batteries. Over time with the generator running, my batteries are completely depleted due to L2 loads even though the generator is large enough for all loads and charging the batteries.

Are there settings I change in the Quattros or do I need an autotransformer?

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3 Answers
mvas avatar image
mvas answered ·

There are at least two ways around this problem ...

#1) Add the Victron autotransformer, which will provide, up to, 16 amps to L2 and the second inverter. 40 amps total = 24 amps (L1) + 16 amps (L2)

#2) Add a 120V 30A isolation transformer to L2+N. Total amps for L1 + L2 must be 45 amps MAX from genny.

The math for the generator ...

45 amps total = 5500 watts / 120 volts

Even though you have two 30 amp breakers, you should only pull 24 amps MAX from each breaker.

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Bruce Orr avatar image Bruce Orr commented ·

I was thinking along a similar path. I thought of adding a small automatic transfer switch (GEYA) for L2 and Neutral. That way when the generator is on, power comes directly from the generator L2 but L1 comes from the master Quattro. When the generator shuts down, the ATS switches L2 back to the other Quattro. Is that what you meant by “Isolation Transformer” above?

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derrick thomas avatar image
derrick thomas answered ·

The issue is that the generator L1 and L2 are in phase and the inverters are split phase configured, so as you found out, they are not switching as group. They are doing exactly what they are designed to do. Is this a Onan generator? If so, you can combine L1 and L2 outputs from the generator and feed the input to one quatro for the full 5500 watts. The second quatro will only be able to invert when running off generator. There is no way around this with your current split phase configuration.

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Bruce Orr avatar image
Bruce Orr answered ·

Yes it is an Oman generator and that was what I was thinking. However with one AC on, only the loads are met ~1800 watts. But there is 30a x 120v available or 3600w on that generator leg. So the batteries slowly drain SOC until the system finally shuts down. Seems like combining the 2 legs wouldn’t help since it not using all the power already available.

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