need some help with 8kw growatt low frq inverter

Hello all, I have a new setup I'm working on, long store ill try to get to it. I have 2 x 100 ah server rack battery connected to my 8kw growatt inverter, inverter output and battery are working fine. its output is split phase 220 volt. all that's good. on the input side ( I'm off grid so no grid ) but I have a single phase honda 2200 I ( for battery charging and testing battery charging now ) connected to a Victron autoformer , output is split-phase 220 volt on my meter at 60 hz but on the inverter screen, it shows as 262 volt which is still below the high voltage cut off (273?) so at first the grid icon would just blink it would not sync. So I had a 500-watt light to the honda to put a load on it and sure enough, it then syncs with the inverter and bypassed power through to the output of the inverter ( off battery use at this point ) but it is NOT charging, the charge light will not come on... So I tried to simulate the grid with a 1500-watt inverter I have ( instead of honda 2200 ) that inverter ( on a different battery bank ) did sync faster and after a min, it went into charge mode( the 8kw inverter ) and started charging the server rack battery . . back on the honda again I even tried bypassing the auto former in case it was the issue but this inverter ( the 8kw ) has to have input split phase it would not do anything on single phase other than run off the battery, so is there a way to force it into battery charger mode ?? Im stumped

Your growatt doesn't have a standard charger. It's more like a tank float valve.

Charging begins when voltage (or Soc) is below setting 12.
Charging immediately ends when voltage (or Soc) raises to setting 13.

Absorption and float voltages are ignored.

Growatt are not known for being generator friendly. Often one needs to decrease setting 11 to 10A and increase as permitted.

sunshine_eggo said:

Your growatt doesn't have a standard charger. It's more like a tank float valve.

Charging begins when voltage (or Soc) is below setting 12.
Charging immediately ends when voltage (or Soc) raises to setting 13.

Absorption and float voltages are ignored.

Growatt are not known for being generator friendly. Often one needs to decrease setting 11 to 10A and increase as permitted.

Click to expand...

mine is 48-volt growatt , but the charge mode is probably about the same, it has charge setting set at 46 volt to 54 or 56 and the battery are at 52 volt. the point was not that it won't charge at all. when I feed a another inverter to it as the "GRID" it goes into charge mode fine..... so it does charge, it doesn't do it when the "GRID" is switched over from another inverter to the generator ... like something about this generator it doesn't like. But I checked the output on the Honda 2200I and its dead nuts at 124 volt and 60 Hz

Even though the AC input voltage is below the max inverter limit, it apparently will not allow connection to source at the higher voltage.

The unloaded overvoltage is likely due to the transformer being unloaded and may be an interaction between the inverter-generator voltage feedback control with the highly inductive unloaded transformer attached. You might check the generator output voltage when you have the unloaded transformer attached.

Be careful allowing it to run too long like this as the higher AC voltage might damage inverter-generator's inverter circuitry. The inverter-generator's output inverter has an L-C filter to clean up its PWM sinewave output. The shunt filter capacitor is creating a parallel L-C resonant tank circuit due to the unloaded transformer inductance that can create a high voltage ringing at the resonance frequency of the transformer inductance and the generator's inverter output filter capacitor.

It may not take too much load to cause the AC voltage ringing to drop to a more reasonable range. Maybe as little as a two-watt load. If the issue is caused by transformer inductive load on inverter-generator, the load may be more effective directly on the generator output side instead of transformer output. Just try load on both sides of transformer to find the lowest wattage load needed to drop the voltage down.

I use step up isolation transformers on my Yamaha EF3000i to produce 240vac for my inverters. I have not seen a problem with my LF inverters connecting but I have not actually checked the generator output voltage before inverters connect. The inverters show normal AC input voltage once they connect so I had no reason to question generator output voltage.

Thats a great point , so on the input source ( my fake grid ) ( honda 2200 ) I had to connect a 500 watt light ( what I had handy ) to the other output plug to get the inverter ( growatt) to sync and pass power through, but it wont go into changing mode.. but I did not put a load on the growatt output yet as I'm still setting the system up and testing as I go to verify wiring etc. so are you saying to put a load on the growatt output to drop the system output voltage and this may allow it to full sync and start battery charging ???

also I have another inverter style generator ( off brand ) that I'm going to try today to see if it like that one better?

chadjones99 said:

but I did not put a load on the growatt output yet

Click to expand...

Load on output of Growatt will have no effect on the generator connect issue.

When I say inverter-generator's inverter I mean the inverter circuitry in the generator, not the Growatt inverter.

RCinFLA said:

Load on output of Growatt will have no effect on the generator connect issue.

When I say inverter-generator's inverter I mean the inverter circuitry in the generator, not the Growatt inverter.

Click to expand...

ok thanks, yes I had to do that already. At first, when I start the honda 2200 gen , it won't sync at all I get a blinking telephone pole icon on the growatt ... then when I connected a 500-watt bulb to the other output plug on the honda the growatt then synced. meaning it clicked and showed power pass through to the output of the growatt but no charge LED or icon.... just pass thru.... then I tried connecting the output of another battery-powered inverter to the growatt as the " grid " instead of the honda 2200, it synced as before but this time the charge light / and icon on the growatt lite up and the battery started taking a charge ...

If you have AC current from generator going to AC output of Growatt then you have a different issue with charging.

I cannot imagine why you have AC pass through from one AC input source, and see AC sourced battery charging, you would not also have AC sourced charging from any Growatt connectable AC input source.

Only thing I can think of is one AC input source is beginning to get overloaded by battery charging and AC out loads so Growatt backs off charging battery to prevent dragging down AC input voltage too much. If that is case backing down charging current bulk setting or reducing AC out loads should lighten the load on generator. The load on generator (and transformer) is the sum of AC pass through AC out load and battery charging load so you have to keep that sum below capability of generator/transformer.

Most inverter's just release from generator when you overload generator. It doesn't appear Growatt LF has any load shaving limiting of AC input current as I don't see any AC input current CT transformers in unit or any user setting to limit maximum AC input current draw. I only see CT current sense transformers on inverter output transformer.

Maybe an entirely different issue but, I wonder if it has anything to do with the frequency matching circuits not playing well together. My Yamaha has similar issues working with my Aims. The Aims has to be inverting first or the Yamaha wont properly match the frequency and will trip on overload.

HighDesertOffgrid said:

Maybe an entirely different issue but, I wonder if it has anything to do with the frequency matching circuits not playing well together. My Yamaha has similar issues working with my Aims. The Aims has to be inverting first or the Yamaha wont properly match the frequency and will trip on overload.

Click to expand...

Generator is the frequency master. The inverter will slowly slew its freq/phase and voltage to match the generator before closing the pass-through relay.

There is a limit to how far off frequency the generator can be before it is outside of inverter lock range. There is an even tighter limit on generator frequency wobble that can be tracked by inverter. Inverter phase tracking is very slow, so it does not make any sudden phase shifts in AC output. 0.3 Hz/second of generator frequency wobble is about the most a hybrid inverter can track. Constant rpm synchronous generator needs to have a smooth even sound. It will have a 'wha-wha' sound when its rpm varies.

Frequency wobble is not an issue for inverter-generator but it is for conventional fixed RPM generators. Unstable governor control on engine rpm is a common issue for fixed rpm synchronous generators ability to work with a hybrid inverter. Carburetor idle jet port clogging is a common issue causing rpm variance at no load on generator causing frequency variance that prevents hybrid inverter from obtaining initial phase lock with generator.

When an inverter is standby mode, the inverter circuitry should still synchronize its inverter drive electronics clock before closing pass through relay so if inverter is called upon to supply AC output after generator connects it is ready to jump into service in proper phase alignment with what generator is (or was, if generator drops out).

Battery charging on hybrid LF inverter also requires inverter to be phase locked to AC input source to charge from AC power input.

update: I tried my pulsar 3700/4500-watt generator, at first did not sync, then I applied the 500-watt light bulb to another generator outlet, it locked/ sync in and sure enough started to pass thru and charged battery , I had the charge mode set to 10 amps ( as for the honda 2200 which by the way was not overloading it would never lock-in ) and it charges at 10 amps , I was able to bump it up to 30 amps AC charging, anything higher trips the breaker on the generator.
After it was locked in light bulb was turned off and it stayed locked/synced in.. and after that I did not need the light bulb to get it to re-sync every time I disconnected the AC load. it seems that at ( auto former output ) anything over 255 volts into the inverter it won't sync, with the light bulb I would have to cycle it a few times but once it seen a dip in voltage it syncs on generator. the Honda 2200 does not respond the same and has about a 3 volt higher output

RCinFLA said:

Generator is the frequency master. The inverter will slowly slew its freq/phase

Click to expand...

chadjones99 said:

the Honda 2200 does not respond the same and has about a 3 volt higher output

Click to expand...

This is the essence of my WAG (wild ass guess). The Honda is made to parallel with another inverter/generator, so no inverter/generator made to parallel is ever the (master) until it is the first one locked onto frequency. This is my experience with two Yamaha 2000i. They have to be connected, then start the first, then start the second. Any other sequence will result in both gennys tripping on overdraw.

HighDesertOffgrid said:

This is the essence of my WAG (wild ass guess). The Honda is made to parallel with another inverter/generator, so no inverter/generator made to parallel is ever the (master) until it is the first one locked onto frequency. This is my experience with two Yamaha 2000i. They have to be connected, then start the first, then start the second. Any other sequence will result in both gennys tripping on overdraw.

Click to expand...

I somewhat agree the difference is mine is not tripping on overload etc , it just , the inverter will not sync to it. I can get the other inverter generator ( which also has parallel ports ) to sync to the inverter if I apply a load to the generator

It also may have something to do with the honda 2200 being 127 volt output, the pulsar is 124 volt output , after both these units go though the auto-transformer the Honda is stepped up to 258 volts and the pulsar is at 253, It appears anything over 255 and the inverter will not lock onto it

chadjones99 said:

I somewhat agree the difference is mine is not tripping on overload etc , it just , the inverter will not sync to it. I can get the other inverter generator ( which also has parallel ports ) to sync to the inverter if I apply a load to the generator

Click to expand...

Again, Growatt are not known for being generator friendly. Signature Solar by default recommend using a generator powered AC charger to recharge batteries vs. using the on board charger, particularly if you're not going to go with 12kW generator in your case.

chadjones99 said:

I somewhat agree the difference is mine is not tripping on overload etc , it just , the inverter will not sync to it. I can get the other inverter generator ( which also has parallel ports ) to sync to the inverter if I apply a load to the gen

Click to expand...

sunshine_eggo said:

Again, Growatt are not known for being generator friendly. Signature Solar by default recommend using a generator powered AC charger to recharge batteries vs. using the on board charger, particularly if you're not going to go with 12kW generator in your case.

Click to expand...

Honestly, who can disagree with someone with an Eggo Avitar (who doesn't love waffles)?
Add a smaller load to the honda and see if it locks in the phase and lowers the voltage?

got it working ( great ) with the mid-size inverter generator ( pulsar 3700/4500 ) but does not like the honda 2200I

One of the issues with this growatt ( and maybe all ) is that when it reaches its float voltage, instead of going to a slow charge rate it just stops. even though your other charge settings are 14.4 ( or whatever you are using ) I had my float at 13.6 so it just stopped at 13.6, ( battery display showed 75 % SOC ) so I had to bump up my float to 14.4 and it charges to 14.4 now and then stops. ( 98 to 99 SOC )