Growatt Overloading Only When on Generator

[mike616]

I have 2x 3kW Growatt inverters and 2x 24v 200Ah LiFePO4 batteries on my RV. Where I will be staying for the next month, there is virtually zero direct sunlight available to my PV array. I am attempting to charge my batteries with a few hours of generator every day.

I am experiencing some strange overload situations with my setup. Both RV Air Conditioners have soft starts on them. But if I am using the generator, whenever I start one of the ACs, the inverter powering that load goes into overload (not the generator). If I set the battery charging current below 22A, I have no issues running one AC. But if I set it to 30A, as soon as the AC turns on, the load on the inverter reads about 5kW and goes into overload mode. There is nothing running in my RV that would be pulling that much load on one leg. In fact, if the AC really were drawing that much power, I would expect the 20A breaker at the RV's service panel to trip. Furthermore, the generator is only rated for 4050W max surge power and it is not overloading.

I have had no issues running one or both ACs on battery power or shore power.

There appears to be some relationship between the battery charge current and the load on the inverter. I was under the assumption that battery charge didn't get factored into the load on the inverter. In fact, with the battery charging at 22A and the AC off, the inverter load is at about 1%. But even if charging power is factored into the load, I should be under the inverter power rating:

(Battery charging power) + (AirCon Running Power) + (Residual Load) = Total Load
(24V * 30A) + (1400W) + (50W) = 2170W

I have no idea why the inverter running the AC is going into overload or why it thinks there is a 5kW load. Is there something I'm missing here?

 

[mike616]

The only thing I can think is that the generator starts to output dirty power at higher loads and the Growatts can't handle this and freak out.

Generator: Westinghouse iGen4500DFc

The Growatt is set to accept generator power which means it will accept a voltage range of 65-140VAC.

 

[Zapper77]

I have 2x 3kW Growatt inverters and 2x 24v 200Ah LiFePO4 batteries on my RV. Where I will be staying for the next month, there is virtually zero direct sunlight available to my PV array. I am attempting to charge my batteries with a few hours of generator every day.

I am experiencing some strange overload situations with my setup. Both RV Air Conditioners have soft starts on them. But if I am using the generator, whenever I start one of the ACs, the inverter powering that load goes into overload (not the generator). If I set the battery charging current below 22A, I have no issues running one AC. But if I set it to 30A, as soon as the AC turns on, the load on the inverter reads about 5kW and goes into overload mode. There is nothing running in my RV that would be pulling that much load on one leg. In fact, if the AC really were drawing that much power, I would expect the 20A breaker at the RV's service panel to trip. Furthermore, the generator is only rated for 4050W max surge power and it is not overloading.

I have had no issues running one or both ACs on battery power or shore power.

There appears to be some relationship between the battery charge current and the load on the inverter. I was under the assumption that battery charge didn't get factored into the load on the inverter. In fact, with the battery charging at 22A and the AC off, the inverter load is at about 1%. But even if charging power is factored into the load, I should be under the inverter power rating:

(Battery charging power) + (AirCon Running Power) + (Residual Load) = Total Load
(24V * 30A) + (1400W) + (50W) = 2170W

I have no idea why the inverter running the AC is going into overload or why it thinks there is a 5kW load. Is there something I'm missing here?

Are your inverters in parallel or series? Is the generator 120 two legs or 120/240?

Edit I see you have a 4k inverter generator.
You are correct that as the generator load increases the quality of the power drops. Typically most RV generators are modified sine wave, some newer rv generators are pure sine inverters.

 

[mike616]

The two inverters are in parallel running two legs of 120V each. The generator provides 1 leg of 120V. I am connecting that to my RV with a dogbone connector which sends the 1 120V leg to both inverters.

By my math, I'm at about 65% of the generator's running capacity. Should I expect the generator to put out such poor power at that load that the inverters start having issues?

My other thought is that the inverters temporarily lose their synchronization with the generator as the AC comes online. Perhaps this is making the inverter think it's overloading when it isn't.

 

[Zapper77]

If I set the battery charging current below 22A, I have no issues running one AC. But if I set it to 30A, as soon as the AC turns on, the load on the inverter reads about 5kW and goes into overload mode.

22/30 per inverter or is one inverter set to 22 amps and the other set to 0 amps?

if the AC really were drawing that much power, I would expect the 20A breaker at the RV's service panel to trip.

20 amp breaker can take a hefty surge well over 40 amps before tripping, maybe even 60 amps for a split second.

if charging power is factored into the load, I should be under the inverter power rating:

Would need to read up on that inverter capabilities.

 

[mike616]

22/30 per inverter or is one inverter set to 22 amps and the other set to 0 amps?


20 amp breaker can take a hefty surge well over 40 amps before tripping, maybe even 60 amps for a split second.


Would need to read up on that inverter capabilities.

22 amps per inverter which supplies about 20 amps to each battery during charging.

I don't see anything in the manual that discusses this. I think the issue is that the generator outputs dirty power over 50% load and that's causing issues with the inverters.

 

[Zapper77]

22 amps per inverter which supplies about 20 amps to each battery during charging.

I don't see anything in the manual that discusses this. I think the issue is that the generator outputs dirty power over 50% load and that's causing issues with the inverters.

Inverters have a max input power rating, battery charging and AC load count towards your max.

 

[mike616]

Even so, charging at 30 amps and running the AC does not exceed the inverter's capacity (as shown in my previous calculation).

I'm now thinking that dirty power from the generator damaged the inverter. When the AC is on, the inverter output drops to 100V. With it off, output rises to 136V. With a 400W load, it sits at 127V.

 

[OutlawSolar]

My Growatt doesn't like it when the generator frequency drop below 60Hz (when the gen is overload). It'll disconnect the generator.

 

[Brett V]

An inverter generator shouldn’t be a problem as far as frequency or voltage regulation. Do you have the Growatt AC voltage range setting on Gen or UPS? When you’re in bypass, the generator needs to have enough capacity to supply the loads in the RV and the charger. Have you tried lowering the maximum charge current from AC?

 

[Zapper77]

Even so, charging at 30 amps and running the AC does not exceed the inverter's capacity (as shown in my previous calculation).

I'm now thinking that dirty power from the generator damaged the inverter. When the AC is on, the inverter output drops to 100V. With it off, output rises to 136V. With a 400W load, it sits at 127V.

30x26x1.1x2 plus base load of 1500 watts
30 amps x 26volts x 1.1 conversion loss x 2 inverters plus base load. Total watts 3,300 ish

That generator is only rated for 3300 watts on propane.

 

[mike616]

Right, but the generator is not overloading. The inverter is.

 

[Browse]

Don't most inverters automatically pass through generator power to the loads? The only way I know to work around this is to use a Chargeverter connected to the generator, with it's output connected directly to the batteries so that the inverter doesn't see any AC input. This is how I get my 12k Growatt to power my 4-ton HVAC unit while using my Honda generator to charge the batteries. The generator alone can't handle the inrush current of the compressor, even with a soft start installed. This also helps reduce voltage sag on the batteries during surges and also ensures the entire output power of the generator is converted to useable energy (minus the conversion losses).

 

[Mattb4]

The two inverters are in parallel running two legs of 120V each. The generator provides 1 leg of 120V. I am connecting that to my RV with a dogbone connector which sends the 1 120V leg to both inverters.

This arrangement does not sound right. If you are in parallel you probably should be only supplying one inverter from the generator but if instead you are stacked supplying 240vAC split phase you likely need a 240vAC generator with 1 hot leg going to one inverter and the other leg going to the other. Double check the wiring diagrams in your manual for proper setup.

 

[mike616]

This arrangement does not sound right. If you are in parallel you probably should be only supplying one inverter from the generator but if instead you are stacked supplying 240vAC split phase you likely need a 240vAC generator with 1 hot leg going to one inverter and the other leg going to the other. Double check the wiring diagrams in your manual for proper setup.

The two inverters are in the same phase. This configuration is consistent with the inverter manual.

 

[Mattb4]

The two inverters are in the same phase. This configuration is consistent with the inverter manual.
View attachment 156412

Actually it is not if you are supplying two hot legs out that read 240vAC between them. You can not get 240vAC in parallel. You instead get 120vAC at double the current capacity.

But leaving that aside it would seem that one of your inverters in not working with the other when you have the generator hooked up to both. It could be a communication issue or it could be a sharing issue.

 

[mike616]

The only way I know to work around this is to use a Chargeverter connected to the generator, with it's output connected directly to the batteries so that the inverter doesn't see any AC input.

This is the ideal solution. If I could get the chargeverter in 24V, I'd buy it in an instant. I've found a few battery chargers that can max out at 35 charging amps at 24 volts, but that just won't be enough to offset the AC.

30x26x1.1x2 plus base load of 1500 watts
30 amps x 26volts x 1.1 conversion loss x 2 inverters plus base load. Total watts 3,300 ish

That generator is only rated for 3300 watts on propane.

I wasn't taking into account the conversion loss and was assuming the batteries were at 24V, not the actual 26V so my estimates were low. Thanks for the correction. I think I was approaching generator overload and that was sending dirty power to the inverter and making it think it was in overload.

Moral of the story, this generator isn't big enough.

 

[mike616]

Actually it is not if you are supplying two hot legs out that read 240vAC between them. You can not get 240vAC in parallel. You instead get 120vAC at double the current capacity.

The two hot legs do not read 240V between them. They read 0V between them because they are the same leg coming off the generator.

 

[Mattb4]

The two hot legs do not read 240V between them. They read 0V between them because they are the same leg coming off the generator.

Thanks. Because you said that you wired each inverter to a separate leg I misunderstood your setup. In essence you only have one leg. Glad you figured out that your issue is the too small generator.

 

[Zapper77]

Thanks. Because you said that you wired each inverter to a separate leg I misunderstood your setup. In essence you only have one leg. Glad you figured out that your issue is the too small generator.

Each inverter is running a separate leg in his RV.