What size generator?

12VoltInstalls said:

It weirded me out for a few years (and still does!) that I can do whatever I want without a grid connection (within limits but the limits aren’t a big deal). I have no generator either.

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But it's a nice weird to have, ain't it?

Saw this video on Victron's 'dynamic assist' feature that provides a 'rate of change' limiting on AC input. This feature is probably most useful for inverter-generators in ECO mode where generator rpm is modulated based on AC output load on generator.

The difference between 'limiting AC input current' and 'dynamic assist' is limiting AC input does not start the inverter reaction time until AC input current limit is reached, while the 'dynamic assists' starts the inverter supplement as soon as AC input current starts to rise before AC input current limit is reached, then gradually backs down inverter supplementing assist to let AC input take the limit of AC input. This gives the inverter feedback control a jump on covering a sudden surge, not having to wait until AC input limit is reached before it gets involved. This should reduce initial surge leak-through to generator, like starting an air conditioner.

The obvious advantage to inverter-generator variable rpm ECO mode is lower generator noise and some fuel savings.
Disadvantage is, in response to a step increase in AC load, the inverter-generator has to increase its engine rpm which takes a second or two. During this rpm ramp up, the generator's alternator is unable to supply the peak load current so the output AC sinewave voltage peaks from inverter-generator's inverter are clipped.

For a conventional synchronous fixed 3600 rpm generator there is a lot more stored mechanical energy reserve in the 3600-rpm rotating engine flywheel. Just need a good stable engine speed governor control that does not vary with generator loading to keep generator AC output frequency from varying too much, which if more than about 0.3% per second wobble, will cause inverter to be unable to track phase with generator and causes inverter to release from generator.

I ordered the eg4 30A charger from Signature Solar. It’s permanently connected to my bus bars and charges my two 24v Lifepower4 batteries without issues. I use a Honda EU 2000 generator when charging.

solarnewguy33 said:

I ordered the eg4 30A charger from Signature Solar. It’s permanently connected to my bus bars and charges my two 24v Lifepower4 batteries without issues. I use a Honda EU 2000 generator when charging.

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Do you not have an inverter_charger or all_in_one?

All in one. Growatt 3kW Stackable Off-Grid Inverter | SPF 3000TL LVM-24P

solarnewguy33 said:

All in one. Growatt 3kW Stackable Off-Grid Inverter | SPF 3000TL LVM-24P

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I'm curious why you would use a dedicated charger when your Growatt has an ac2dc charger built in?

I guess I didn’t trust the growatt. I also bring the batteries home in the winter and wanted to option to charge at home with my grid ac. I leave the growatt at the cabin year around. Still figuring it out and probably making mistakes along the way. I just bought the cabin this season so over time I’ll probably fine out what works best.

John Frum said:

I'm curious why you would use a dedicated charger when your Growatt has an ac2dc charger built in?

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Wouldn't it have the same issue we are discussing above though? That is if he uses the all-in-one to charge then his AC loads through the unit are also attached to the generator?

photomankc said:

Wouldn't it have the same issue we are discussing above though? That is if he uses the all-in-one to charge then his AC loads through the unit are also attached to the generator?

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The efficiency is lower for the ac loads with a dedicated charger.

With the all_in_one charger the ac loads are powered by the generator and the battery is charged by the all_in_one's charger.
There is no conversion loss for the ac loads and ~80% conversion efficiency for the battery charger.

With the dedicated charger there is ~80% efficiency for the charger(ac to dc conversion) and a compounded 85% efficiency for the inverter(dc to ac conversion).

That is ~68% overall efficiency for the ac loads vs 100% efficiency for ac bypass.

That's great... if you have the watts to do both. If you have 1800 running watts to charge and supply the cabin you don't have a lot left over. Efficient or not.

For me generator use is throwing idealism out the window for a couple of hours and running a dirty inefficient setup for pure convenience. My actual top priority with generator use is first to protect my batteries from duress, and 2nd to not have to listen to it orinteract with it any more than necessary. To that end, a relatively small (relatively quiet) generator powering ‘seamless’ dc charging (as in the inverter can’t complicate it or screw it up in any way), on the end of a long extension cord 100ft away so i dont have to hear it, fits my motivations.

Its not a ‘green’ way of thinking, but if i want to listen to engines ill play with my cars and tractors. I’ll gladly trade away efficiency to be able to pretend im not using a generator, when i am. Anything else for me, is turd polishing. ?