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Will generator work with Growatt?

atWar

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Mar 29, 2021
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Has anyone successfully used a generator as backup with a Growatt inverter/charger? The user manual for the Growatt 3000 TL 24v says,
Note: When connecting generator, the generator should be no less than 10KVA
and
(Only diesel generators allowed)
So, can it be that only 10000 watt diesel generators will work with this unit? Does that mean my 3500 watt gas genset won't?
 
I have a pair of the same Growatt units, but the 48V versions, though I did not notice that in the manual. I have a 3500W gas generator that I intend to test at some point.

That seems like an oddly-specific requirement. The only technical reason I could see for the requirement is when the inverter transfers to AC bypass. The genset will go from 0 current, to potentially a large load in an instant. That could be pretty rough, and smaller generators may bog down/stall. Likewise, diesel gensets typically have more torque, and would deal with that better. I have observed the utility charger to have a soft start, ramping up the charging current.

I can't see smaller gasoline gensets being an issue, with some common sense:
1. Load management. If you have to manually start the generator, disconnect some of the loads before connecting to genset.
2. Set max utility charge current (program #11) appropriate to genset size. For example, with 3500W genset (~30A max) and typical loads ~15A, then I need to set max utility charge to something less than 15A (probably more like 10A).
 
Thanks fazeshift. That makes sense. Please post your results if you get a chance to test your generator. I am off-grid and have no big loads to speak of so should work but it would be nice to know someone has done it.
 
Sure - I will post results, but it may be some time until I get everything else in the system finished up.
 
I was hoping to the GroWatt or MPT split phase all-in -one inverter with a Propane generator I've purchased from a local RV salvage yard! I've read in the respective manuals that eiither one will/should work but haven't found anything on youTube U that demonstrated this. I also have a RV coach with a gas generator and there is a simple SPDT switch that starts and then kills the generator at the users request. I'd envisoned using the gererator 110 V to power the input to the inverter where this would power my loads and the charger to the capability of the generator, Any info is appreciated. This seems to be one of the remaining missing pieces to the puzzle of an off-grid system I'm planing.
 
I was hoping to the GroWatt or MPT split phase all-in -one inverter with a Propane generator I've purchased from a local RV salvage yard! I've read in the respective manuals that eiither one will/should work but haven't found anything on youTube U that demonstrated this. I also have a RV coach with a gas generator and there is a simple SPDT switch that starts and then kills the generator at the users request. I'd envisoned using the gererator 110 V to power the input to the inverter where this would power my loads and the charger to the capability of the generator, Any info is appreciated. This seems to be one of the remaining missing pieces to the puzzle of an off-grid system I'm planing.

I have a cheap lp gas "inverter" generator which charged fine. My Growatt is the 48v version. This test run was limited to 40a on the Growatt. No faults were displayed while charging which indicates to me that the power requirements were met. The voltage stayed between 118-120v and Hz stayed right at 59.9. There is another thread discussing what the actual requirements are, discussions with Growatt Etc, i found this useful https://diysolarforum.com/threads/generator-types.18241/.

From what I've gleaned from the above link the "inverter" part isn't necessary "I was shopping for a generator yesterday to connect to my Growatt SPF 6000T. I had the same question about needing a generator with pure sine output. I called support at Watts24/7.com (where I bought my Growatt) and they said there is no need for a pure sine generator input to the Growatt. He did mention it is important that the output frequency is relatively stable. I bought a Predator 6500W from Harbor Freight, and will be installing it this week."
 
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Has anyone gotten any more info on this? I am in the process of installing a growatt in my RV and read about only Diesel Generators allowed on the growatt. Now i am worried.
 
I ran the generator test today, and the results were good.

The test was run with a single Growatt SPF 3000TL LVM, the 48V version. I have a pair of them, but the 2nd was fully disconnected for this test. The generator is 223cc gasoline and rated for 3750W continuous, 4750W surge. It is branded WEN, but is the typical clone of a Honda engine found on many inexpensive imports.

I set the grid charging to 25A, which I calculate would be a 1700W load to the generator, assuming a generous 80% charger efficiency. Connected loads were around 2kW, so about 3700W total load on the genset. The charger ramped up to 25A over ~45 seconds, and I did not notice any signs of strain to the generator.

I'm considering posting video, if there is interest.
 
For any hybrid inverter the generator frequency has to be in the range allowed by inverter otherwise the inverter will not be able to phase lock to generator AC output.

If you have been using hybrid inverter to push power to grid the allowed AC freq range may be quite tight, like +/- 0.3 Hz. This is difficult for a generator with a mechanical govenor to keep. You may have an inverter setting to allow more AC input frequency range.

Also if 3600 rpm (3000 rpm for 50 Hz), the govenor speed control must provide a fairly constant rpm. If you hear it varies rpm speed (waw-waw sound) the inverter cannot lock on to a rapidly changing AC line freq.

If inverter-generator don't use ECO mode. When inverter-gen in ECO mode is initially loaded its AC output voltage will dip as engine speeds up to final required rpm. This may cause inverter to disconnect from generator.

On inverter side, if the inverter allows limiting max AC input current set it below level capable of generator. If not, make sure your charger setting does not overload generator., In that case you also have to manage your loads manually. Most hybrid inverters allow you to do AC input load shaving which is limiting the maximum AC current drawn from AC input. In that case you should be able to draw a peak AC current output that is the sum of what generator can put out plus maximum of inverter output on batteries. (within limits of inverter pass-through current for gen input).

Sometimes if you turn on a heavy surge load device, you may hear the generator bog down with load and inverter may disconnect because the generator rpm dropped causing AC input frequency to drop out of tracking range of inverter. This in-turn may overload inverter causing it to shunt down from overload.
 
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You should see this video... in fact all growatt owneers should watch this....

Well, the guy in the video says that the generator must feed the load and the charger and my recent experience tell me otherwise. It depends on the settings because for my Growatt SPF 3000, it was charging the battery but AC output was from the inverter (battery + solar feeding it). My device will be in Bypass mode to feed the AC out from the AC in or at least that is what I think. Fairly new to solar for my remote chalet deep in the wood... I will post my experience with a generator separately.

He also puts everyting in the "Inverter" module, but it's more complex than this. The inverter part converts DC to AC for output, the charger module converts AC (grid/generator input) and or DC (Solar) to DC. Not sure about the design of the Growatt but probably that AC to DC and Solar DC to DC are separated charger modules???
 
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I have a Growatt SPF 3000 LVM 48V that has been installed a few weeks ago at my off-grid-cellular-... chalet. I have 16 LifePO4 200 Ah cells. My generator is a Generac 3250. If I hook the generator to the AC input the Utility Pole flashes and is not used. I checked the signal and voltage is in the range but frequency is over 70 Hz with no load. I reduced the throttle to get it down to 60 but it would not work. Then I decided to connect my 48 V charger to the generator and that works well. I connected the charger to the positive bus bar and the negative to the P- of my BMS. According to a video posted in this thread, this is not recommended at all without turning the Growatt inverter first but what is the point of charging for a few hours if you cannot have power during that time?

Anyways it worked without any damage so far. I then turned the AC input switch ON to feed the Growatt with the L2 120V leg of the generator, L1 is used by the 48V charger) and the Growatt started to charge the battery using the AC input. So my guess is that having a load on the generator help get a more stable AC input. So for a while I have two chargers.

My conclusion and guessing is that small power non-Inverter type generators are not good to use as an AC input and using a separate charger is probably best. I will buy a Honda EU7000IS which is 5.5KW steady inverter generator and pretty sure that will work well. I prefer using the Growatt charger because it can deliver more power than my 48V charger (rated at 25A max) and the Growatt will monitor the AC input (aka Grid) and that will reflect in the reports and dashboard.

This is my setup, on the left the 12V system that came with the chalet (in the crawling space of the chalet, I hate working on my knees so I moved it to the shed). It's not finished yet and should put a rock board behind the Growatt and some wires should be in conduits by code but it's a remote chalet and I'm new to solar systems.
 

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In general I think these AIO units like a quality AC supply, so an inverter generator is a much better bet.

I can't speak for the Growatt but my generic 48V 4kW AIO Voltronic clone works perfectly with the AC power supplied by my Yamaha EF3000iSE inverter generator.
 
There is a lot of marginal truths in the video. I think the guy is promoting his separate chargers.

There is no fixed rule of 60% loading on generator. It depends on generator quality and reserve margin.

Some synchronous generators (non-inverter type) do have poor quality sinewave output. Some have excellent sinewave output and maintains good quality at high percentage loading. Newer synchronous generators have electronic rotor field winding regulators and stepper motor throttle control.

There are two generator parameter that are very important. First is freq accuracy that most folks know about. Second parameter not so well known is freq stabiliity. For synchronous generators this means rpm governor control stability.

Hybrid inverters phase lock to AC input, match AC voltage and run in parallel with AC input when input relay closes. First it must be within freq range of inverter. Some hybrid inverters with two different AC inputs have a tighter freq range for input typically used for grid and a wider freq range for input typically used for generator. The wider the allowed freq range the longer the inverter connect time. So for faster connect time it is better to only search for a narrower freq range if you know AC source, like grid, stays within the narrower range.

Achieving and maintaining phase lock to a generator is highly dependent on generator's freq stability. Most hybrid inverters will not lock or stay locked onto a generator that has more than about 0.3 Hz per second rate of frequency wobble, due to an unstable rpm govenor.

If a generator boggs down under load where rpm drops the hybrid inverter may release from generator resulting in all AC output load having to be picked up by inverter. If loads exceeds inverter's VA capability then inverter will also shut down.

The phase lock tracking by a hybrid inverter is very slow. Generator must have a relatively stable frequency within the inverter's freq spec range.

High frequency hybrid inverters are more 'delicate' to any AC backflow power surges than low frequency hybrid inverters. You should try not to allow a generator to run out of fuel while connected to hybrid inverter. An inverter-generator is best bet for a HF hybrid inverter. They have very accurate frequency and good sinewave quality. In ECO mode (variable engine speed) they may have a sinewave voltage peak slump when an AC load is first applied until engine rpm rises to meet the new demand. If you need AC motor startup surge current it is better to keep ECO mode off.
 
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I don't know about Growatt, but with my AIO (Must PV1800 VMPK - 3KW) :
I tried charging with a non-inverter 3.5KW gen I have. It refused to accept it.
I tried it with a small (750W) inverter one. It worked, but the gen went into overload within some five minutes. Charger absorbs some 5-600W.
I tried it with a 2KW inverter one. It works just fine.
I bought a 2KW inverter one. It was broken (brand new). They changed it for a new one on warranty, I put it inside a wooden box with fans working off the DC output, it's nice, quiet and efficient :·)
 
When running a hybrid inverter from a generator you must control the inverter maximum AC input current to stay within limits of generator.

The AC input draw for a hybrid inverter is a combination of AC output loads and battery charging power.

When an inverter has a setting for limiting maximum AC input current draw it will distribute that power between AC output loads and battery charging with AC output loads taking priority over charging. If AC output loads is greater than AC input current allowed then the inverter/batteries may suppliment the generator's power to meet the AC output demand.

This is one of the weaknesses of HF hybrid inverter. If it is charging battery and a heavy AC output load shows up, a HF inverter cannot mode change from charging to inverter mode quick enough. LF hybrid inverter has no problem doing this.
 
you must control the inverter maximum AC input current to stay within limits of generator.

I did... within the limits of the inverter/charger. Set it to 20A (at 24V, minimum allowed).
25x20 is 500 (W). It drew 5-600 (measured - which makes sense, it needs more than 25 to charge). The generator is rated 900 peak, 750 continuous.
Which just confirms that ratings are always... optimistic :·)

[EDIT] Yes, it was on "bypass" - loads first, battery second. When testing charging, I minimised loads to... next-to-nothing :·)
 
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Does anyone know if the Predator invertor generator 3500w will work to directly plug into the Growatt 3000w 24v model? Or is it better to have separate battery charger? Thanks in advance.
 
There is no reason for an inverter generator to not work with the Growatt and you will not need a separate charger. Some say we should not plug a charger while it's connected to the Growatt but I did a few times to charge faster and had no issues so far.
 
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