Generator back up charging strength w/ brands?

[Stewfish]

​

I'm looking at the Growatt 24v SPF 3000TL LVM. I like it bc it has MPPT, has parrellel already included, has generator backup auto start, 24v for modern car battery conversions like bigbattery, 140v and 2000w input seems good enough, and stacked will give me 6kw when I really need it.

Growatt disclaimer, " The generator is a different beast to the solar charging. It does not use bulk or float charging" You set parameters 12 and 13 for the generator to turn on and off. Then set parameters 11 to charge amperage - too much will stall the Genny or cause it to go out of phase. So how high can it charge?

I was looking at Will's website and that sent me to another website with the all-in-one inverter/controllers and I saw MPP and Growatt. I noticed that grow watt had a disclaimer in their description. Under the utility power input it had 60a which sounds great, but I'm a bit confused though.

Do the Growatt and MPP trickle charge the batteries? If not how high have you set it?

The main scenario I foresee is that we run the batteries down over 3 cloudy days then the generator will automatically turn on. Then I assume our 3500 watt generator by going through the grid input will output the max 60 amps and runs stuff as well as charges the batteries with what's not being immediately used. I could swap with my dad's 7000watt generator to charge faster.

So the big question, does it charge the batteries at a trickle like 5amps or something and will take all day running to fill up? Are we going to get up to the max amperage from our genny charging the batteries, minus anything used immediately? Maybe a hard start capacitor would help at Genny start up?

If it is a trickle charge - long shot - Next comes to mind is use the generators front AC plug to add to the Growatt slow charging by essentially having the AC plug on the front of the generator go to a 20a plus charger that charges the batteries. Maybe a 24v boat charger.

Their warning has me worried the system would suck in the scenario above and I would have to run the generator until the sun came back out and the solar array then charged the batteries back up again. We would have two controller running a 15kwh battery bank (3 of the bigbattery .com banks on Will's site). Do I need two generators? One for each controller?

In worry bc many RV chargers have a slow float charge that sucks and I have experienced having to run the generator all day to charge up the RVs' 2 small batteries. So many people tear out the old charger and add their own 40 amp chargers.

 

[snoobler]

Without context, hard to say - 60A is likely the battery charge current maximum. It does not behave like the 14.4/13.8V charge profile in a RV converter - though the converters generally get to 80-90% charge very quickly and obsessing about getting the batteries to true 100% is typically not productive. If 10% eats up your margin of error, you have a poorly designed system.

"trickle charge" has no meaning. If you meant to say "float", then yes. They do.

They charge the battery through a 3 phase bulk, absorp and float method designed to fully charge the battery regardless of source (grid, genny or solar) if programed properly.

You can limit the charge current by source and total across all inputs.

If you read through the manual for the various settings, you'll understand more.

 

[gnubie]

I'm pretty sure you can set the AC charger current limit in these units but if you post a particular model MPP that can be checked in the manual. Apart from that the charger will run full tilt in line with the charging voltages etc. Effectively full power in bulk mode, tapering down in absorption, minimal in float (unless the battery is partially discharged but not low enough to trigger bulk, in which case current rises to bring the battery back to float voltage).

It's important that what ever charge rate is set the generator must be capable of supplying the power to carry it. If the inverter wants to draw 12A off it's AC input but the generator can only supply 6A the generator will be overloaded and might shut down etc. No inverter I'm aware of automatically adjusts it's AC charger power to try to match it to the capabilties of the generator. If the generator drops off frequency or far enough out of voltage range the MPP will probably detect mains / grid fail and take what ever action it is configured to do.

 

[Stewfish]

Sorry guys I was looking at stacking 2

Growatt 24V SPF 3000TL LVM –​

I updated the disclaimer in the 1st post

 

[Stewfish]

I'm pretty sure you can set the AC charger current limit in these units but if you post a particular model MPP that can be checked in the manual. Apart from that the charger will run full tilt in line with the charging voltages etc. Effectively full power in bulk mode, tapering down in absorption, minimal in float (unless the battery is partially discharged but not low enough to trigger bulk, in which case current rises to bring the battery back to float voltage).

It's important that what ever charge rate is set the generator must be capable of supplying the power to carry it. If the inverter wants to draw 12A off it's AC input but the generator can only supply 6A the generator will be overloaded and might shut down etc. No inverter I'm aware of automatically adjusts it's AC charger power to try to match it to the capabilties of the generator. If the generator drops off frequency or far enough out of voltage range the MPP will probably detect mains / grid fail and take what ever action it is configured to do.

I updated the post, yeah it warns it doesn't do bulk charge and will go out of phase if charging in parameter 11 is set too high. So how do I know if it goes out of phase. Just wait for the inverter to tell me? I'm hoping to get 20amps at 120v as my Genny will do 30 amps at 120v so that would be a lot better than a trickle charge. Does anyone know how high you can get to the running load of your Genny?

 

[gnubie]

Some generators have frequency meters on board, but that won't tell you if the output is unstable just its mid-term frequency. Apart from monitoring the AC yourself you'd just have to wait for the inverter to complain. Inverter generators are very frequency stable but you trade that for less stability in voltage, ie high loads still run close to on frequency but with reduced voltage.

 

[Stewfish]

Some generators have frequency meters on board, but that won't tell you if the output is unstable just its mid-term frequency. Apart from monitoring the AC yourself you'd just have to wait for the inverter to complain. Inverter generators are very frequency stable but you trade that for less stability in voltage, ie high loads still run close to on frequency but with reduced voltage.

I do remember scrolling through my Genny screen and seeing the hertz. I think it will be fine.

Note: At 60a with 25v = 3500w so I guess that's the biggest Genny the box can use anyway.

 

[Jeff cox]

Have you had any luck charging your system with a generator? I have the growatt all in one spf3000 48v system. Little 5500w generator won't charge the batteries at all. It starts to, goes for about 45 seconds then the system kicks off the incoming power and the generator grinds a little. Older generator, so I'm not sure if it's the THD output of the generator. Don't wanna spend extra money for another generator that still won't work......

Anyone else have this issue?
What generators work for the system?
Is this THD (total harmonic distortion) as important as some make it out to be??

Thanks

 

[schmism]

Have you had any luck charging your system with a generator?

I think I have also seen complaints of the HF all-in-one's complaining about the "stability" of the generator power you feed them.

I told the wife as we come into the winter I should fire up the generator and see if my growatts will actually run off it. I have 2 diffrent versions, a newer inverter style only good for about 1400w and the old school 8hp Tecumseh which will do like 6kw. I know my Tecumseh does suffer from frequency varraion as it surges under light or no load.

 

[Stewfish]

I updated the post, yeah it warns it doesn't do bulk charge and will go out of phase if charging in parameter 11 is set too high. So how do I know if it goes out of phase. Just wait for the inverter to tell me? I'm hoping to get 20amps at 120v as my Genny will do 30 amps at 120v so that would be a lot better than a trickle charge. Does anyone know how high you can get to the running load of your Genny?

The setting was so you don't over tax your Genny at startup. Looks like it will work okay, but I haven't finished installing them

 

[atWar]

The setting was so you don't over tax your Genny at startup. Looks like it will work okay, but I haven't finished installing them

Did you ever get your generator to work with the Growatt. I am trading my lead acid for lithium but I will still need a generator backup for the solar so I need to know if the 3500 watt generator will work.

 

[MichaelK]

What the inverter is doing is "qualifying" the incoming power from the generator. It wants "quality power". The inverter has a default setting, and in this case that setting appears to be 60A. On my inverter it is 140A.

So, you do this in two different ways. Either you scale the generator to handle the defaults, or you scale the charging to match the generator. With a smaller generator you'll reduce the charging rate in the inverter's settings to accomidate what the generator puts out. Most likely you will have to play with the numbers to get it just right.

A good rule of thumb is don't try to push the generator at past 50% of capacity. That might work. What I see with my own generator is that it will only qualify at low amperage values at startup, but once the generator is warmed up, the charging rate can be inched up about 3-fold what the startup rate was.

 

[atWar]

My current low frequency inverter charges up to 110A at startup on power from a 3500 watt genset. The genset AC output is 30A. That being the case surely this genset will power the Growatt charging at 60A?