using a generator to go around the utility input on a hybrid inverter/charger

[mesquito_creek]

System: MppSolar LV6048 with a 48V LifePo4 battery bank.

My problem is that I don't have a large enough generator to provide the Utility Input when I am running heavier loads. One of my problems I have discovered with my MppSolar inverter is that when it switches over to the Utility mode it must provide both the load and the battery charging from the generator. If I have a load (AC unit) running the load will over load the generator and fault. I was hoping that I could configure it to just use the ultility/generator input to just provide additional charging to the battery bank, but still remain in battery mode to provide the load. That is not possible from what I can tell.

There are times when I may run the AC into the night after there is no PV charging the battery. Eventually after a few hours the temp will come down and the AC will automatically shut off. If I am at a bit of a deficiency on my battery storage a few hours of a 1600Watt generator will extend my power demand and get me where I need to be.

Can I just go around the inverter charger and hook up a 48V lifePo4 battery charger directly to the the busbar on my battery bank and supply the battery charger with my Predator 2000 inverter generator to charger? The battery charger may not actually charge much or at all if the demand is over the amps being supplied, but would it just be consumed by the inverter in those cases and supplement the amps coming out of the battery bank?

obviously my first choice for the battery charger will be an EG4 25 amp via the affiliate link on Will's website. The generator should power that charger with about 14 amps to provide something within the 5a-25amp range on the charger.

 

[HRTKD]

Yes, you can do that. Think of the power at the bus bar as a reservoir. The battery is putting power into the reservoir to run the inverter. If you dump more power into the reservoir (from the charger), it's available to whatever is looking to consume power. In your case, it most likely will be the inverter that consumes all of the power coming in from the charger.

Let's say you dump in 1000 watts from the charger (unlikely, but work with me here).
1. The inverter needs 1200 watts. The 200 watt deficit will come from the battery.
2. The inverter needs only 800 watts. The surplus 200 watts will go to the battery, if it needs it.

 

[mesquito_creek]

Yes, you can do that. Think of the power at the bus bar as a reservoir. The battery is putting power into the reservoir to run the inverter. If you dump more power into the reservoir (from the charger), it's available to whatever is looking to consume power. In your case, it most likely will be the inverter that consumes all of the power coming in from the charger.

Let's say you dump in 1000 watts from the charger (unlikely, but work with me here).
1. The inverter needs 1200 watts. The 200 watt deficit will come from the battery.
2. The inverter needs only 800 watts. The surplus 200 watts will go to the battery, if it needs it.

Thank you, that is exactly how I believe I need it to behave. The mpp inverter can deliver the spike load as the AC cycles on and off, the Generator alone can not. When the AC and a fridge is running I am using about 1500-1900 watts. The small generator can not get past the point that the mpp inverter utility input trys to switch everything to the Utility bypass. the Generator trys with 3-4 motor surges and then throws the breaker. With combined input of the battery bank and generator the inverter will just see it all as battery mode. As AC/Fridge cycling I am hoping I can tread water on the battery bank when I am a bit under storage and no PV to keep things alive.

 

[HRTKD]

Check to make sure your cables are sized appropriately. Small wires can cause problems when there are large current draws.

 

[Sojourner1]

Can you turn off the charger while it supplies the ac input power? On my Magnum remote for the hybrid inverter/ charger I can turn off the charging option so all power is going to the 120vac when using the generator.

I should add that during the day the solar will carry the dc loads and charge the batteries.

 

[mesquito_creek]

Can you turn off the charger while it supplies the ac input power? On my Magnum remote for the hybrid inverter/ charger I can turn off the charging option so all power is going to the 120vac when using the generator.

I should add that during the day the solar will carry the dc loads and charge the batteries.

If you are referring to the utility input on the mpp inverter, I don't think so, the lowest setting is 10amps.

If you are referring to the charger/generator that would be connected to the battery buss, then yes. There is a switch and the generator can be turned off.

 

[mesquito_creek]

Check to make sure your cables are sized appropriately. Small wires can cause problems when there are large current draws.

Which wires are you referring to? The wires coming from the battery charger, that is connected to the battery buss bar (in the future)?

Or the wires currently connected to the utility/generator on the mpp inverter/charger?

The current utility input that I can connect to the generator (with the unsuccessful results) is a 10 gauged 120v 3 prong plug about 36 inches long. It also is jumped across the 240v input like Will did in his video for the mpp LV5048, so I even have that inefficiency as part of the problem.

This really hasn't been a problem because I just avoid this off grid RV if the weather is hot and requires that much AC... But I have to be there at the first of august and I want a little bit of a back up strategy if I need to stretch the capacity of my battery bank in the no sun hours of my stay....

 

[mesquito_creek]

The correct solution is for me to add another 3000 watts of PV array on the unused mppt on my inverter and point it west to get some more solar capture later into the afternoon. But I hate to invest another 2000 dollars on that if I can limp through a couple of days here and there in the occasions I am there.

 

[Sojourner1]

Does your hybrid inverter/ charger have a remote control that you can make adjustments with in the settings. With in theses settings there might be a option to turn off the charger so only the incoming ac power from the generator is going to the loads, if that's what you want.

Here is the remote for my Magnum and it's right there as an on/ off button but I believe some you have to go into the menu for it.



In this image the charger is on so the generator (eu2200i) is running and 16a is set as the incoming loadshare. The inverter/ charger is charging at 115a showing on the Magnum remote and the balance from solar showing on the GBS display "charging".

 

[HRTKD]

The current utility input that I can connect to the generator (with the unsuccessful results) is a 10 gauged 120v 3 prong plug about 36 inches long. It also is jumped across the 240v input like Will did in his video for the mpp LV5048, so I even have that inefficiency as part of the problem.

That sounds like the right size.

 

[mesquito_creek]

Does your hybrid inverter/ charger have a remote control that you can make adjustments with in the settings. With in theses settings there might be a option to turn off the charger so only the incoming ac power from the generator is going to the loads, if that's what you want.

Here is the remote for my Magnum and it's right there as an on/ off button but I believe some you have to go into the menu for it.

View attachment 56356

It does not support that configuration. Plus the generator is too small to run my load by itself anyways. I am trying to slow down the consumption off the battery bank just long enough to get me into the next solar cycle...

 

[Hedges]

What I've considered by haven't tried is having generator feed DC to PV input of system. One benefit would be generator not used as voltage and frequency source, inverter continues to handle that. Another is generator doesn't see step load or load dump.

There are some issues like inrush current and whether source is ground referenced if simply rectifying AC. Isolating through a transformer and powering a CV/CC supply are possibilities. Some inverters have "turbine" input algorithms meant for wind or hydro, which might work better than PV MPPT.

Ideally inverter can be programmed for arbitrary current limit on AC input. Yours has minimum 10A? is that at 220V not 120V, which is why even that is too high for a 1600W or 2000W generator?

 

[noenegdod]

Ideally inverter can be programmed for arbitrary current limit on AC input. Yours has minimum 10A? is that at 220V not 120V, which is why even that is too high for a 1600W or 2000W generator?

I dont understand this. His generator is rated for 2000W peak and 1600W continuous. 10a at 120 is only 1200W Why would that be to high?

Edit: Just figured out what you were asking. Sorry.

 

[mesquito_creek]

What I've considered by haven't tried is having generator feed DC to PV input of system. One benefit would be generator not used as voltage and frequency source, inverter continues to handle that. Another is generator doesn't see step load or load dump.

There are some issues like inrush current and whether source is ground referenced if simply rectifying AC. Isolating through a transformer and powering a CV/CC supply are possibilities. Some inverters have "turbine" input algorithms meant for wind or hydro, which might work better than PV MPPT.

Ideally inverter can be programmed for arbitrary current limit on AC input. Yours has minimum 10A? is that at 220V not 120V, which is why even that is too high for a 1600W or 2000W generator?

Great idea... I have a un used mppt on my hybrid device. Unfortunately, my little genny only has a 12v 8 amp output and my mppt needs an open circuit voltage of 60v to get it to work. So I would need a weird step up transformer to make the 12v = 60+v and even then it would be limited to 8 amps... IF i understand what you are suggesting.

Ideally inverter can be programmed for arbitrary current limit on AC input. Yours has minimum 10A? is that at 220V not 120V, which is why even that is too high for a 1600W or 2000W generator?

Mine utility/genny input has L1/L2 and is 240v, but I am only feeding it with 120v with L1/L2 jumpered. The configuration of utility charging current is limited to 10A and no apparent way to make it 0A, which would help lower the combined load (live load and charging load). My inverter won't let me separate the two. If I could configure the utility input to only provide battery charging and keep serving the live load off of batteries all this would not be necessary.

So it actually works fine as long as my load is well under what the generator can provide. The genny is rated at 2000 but 1600 nominal. I have lots of PV and battery storage to run everything, even my AC.... until it gets really hot and the night time temps don't come down low enough for the AC to shutoff by lets say midnight.

I just need to know when the weather report says its going to be hot all night and on those days, If I run my genny connected to the battery buss bar at around 5pm when my solar starts producing less than my load, I may be able to supplement my battery long enough to get me to the next morning when the sun comes up.

I am really close now, but if I go a 1 and a half days under these hotter than normal condition I will hit the low DC cut off on the battery bank.

 

[mesquito_creek]

I dont understand this. His generator is rated for 2000W peak and 1600W continuous. 10a at 120 is only 1200W Why would that be to high?

Edit: Just figured out what you were asking. Sorry.

You are correct, except when I want to do this my load is over 1600w and has 2 motor (AC and Fridge) that the spike will even exceed 2000w peak.

The whole 10amp charging deal was to try to eliminate that part of the load to keep me under 1600w.

A soft start on the AC might also help. But at this point I am going to just keep adding more PV and batteries until none of this matters. But I am not doing that in the middle of the summer. Hopefully, just connecting the generator with a standard charger to the battery buss can get me thought the few days this summer I need it.

 

[Sojourner1]

What is the size of your system?

 

[mesquito_creek]

What is the size of your system?

LV6048 inverter 6000watts. 4-48v lifepo4 103 ah batteries for 412 total Ah of storage. I have 4000w of PV which is the max on one of the built in mppts. I have another mppt controllers to add another 4K PV

It running a 50amp style RV off grid. One AC unit and the other misc load runs about 1500 ish watts. 2 ACs and other stuff runs about 3000-3200 watts. I see about 3000-3500 watts of PV input for 3-4 hours and can easily run everything (2ac, fridge etc.).

For example it is 9:52 am and I am making about 2438 watts off the PV array right now. I am in southern utah and I make power from about 730 am until about 6pm. Obviously over a pretty normal curve that maxes out about 3500 under perfect conditions. I am using about 22w (no ac no fridge yet) That early morning PV has my battery bank up to 55.1V 85% soc as we get ready for the heat and everything to turn on in the next couple hours

 

[Sojourner1]

That sounds nice and when the day comes I settle down to a small remote cabin that's about the size of system I would like. ?

 

[Hedges]

Great idea... I have a un used mppt on my hybrid device. Unfortunately, my little genny only has a 12v 8 amp output and my mppt needs an open circuit voltage of 60v to get it to work. So I would need a weird step up transformer to make the 12v = 60+v and even then it would be limited to 8 amps... IF i understand what you are suggesting.

I was thinking of 120Vrms AC output rectified and fed to MPPT input. It would deliver about 170Vpeak.
With an inverter generator, it would have a DC rail of 170V or so (340V or so for 120/240V)
These voltages may reference back to chassis of generator (making it a possible hassle/hazard) or may be isolated.

 

[mesquito_creek]

I was thinking of 120Vrms AC output rectified and fed to MPPT input. It would deliver about 170Vpeak.
With an inverter generator, it would have a DC rail of 170V or so (340V or so for 120/240V)
These voltages may reference back to chassis of generator (making it a possible hassle/hazard) or may be isolated.

AC output rectified and fed to MPPT input... Is that the same thing as saying an AC to DC converter?

Are you suggesting that the MPPT charger method of AC output rectified would be more efficient then my standard AC to DC 48v bench charger on the bus bar?