Hi All

On the journey to going off-grid, I'd like to get a generator that will automatically charge my Pylontech 4.8kwh batteries when they reach a certain %.

Currently, my system is set to prioritise solar, then use batteries and when batteries fall to a specified % to use the grid. I'd like the inverter to use the generator to charge the batteries and only if the generator is inactive, to use the grid.

1. Which generator brand is working for you?

2. What size generator would I need?

3. Should I look at an LPG gas-powered generator vs. a petrol or diesel?

Anything else I need to consider?

This topic comes up from time to time. You'd think it would be a straightforward proposition, but it seems not to be.

You don't say what inverter you have, but most of them work within limits, and that includes grid frequency (mine will disconnect from grid automatically if grid voltage or frequency go too far out of whack). And this is the problem: The generator has to give output that is within the voltage and frequency range. It has to give that when it starts up, and be able to sustain that as the load changes - remember that it is not just the batteries at this point, but the other loads in the house. If the voltage or frequency wander too much then your inverter may decide to disconnect from what it is seeing as the grid.

There's an element of programming here as well. Do you want to keep on charging until the battery is at 100% SOC, or up to a lower level? I presume you want the generator to switch off at this point.

I can't advise on the settings/programming, but I think this is something you need to consider.

You could search the forum for information as similar subjects have arisen before. From memory you need a low revving, good quality generator, rated at at least twice the inverter rating - 16kW in your case.

There may also be considerations around earthing. I don't have the technical knowledge to advise on this, but check on this as it's a safety issue.

Or hang around a while and see if somebody with the necessary technical skills can offer input.

1 hour ago, Bobster. said:

remember that it is not just the batteries at this point, but the other loads in the house

1 hour ago, Bobster. said:

rated at at least twice the inverter rating - 16kW in your case.

@JK84 has a Deye, which allow the inverter to limit the power it takes from the generator. That means that the old rule of needing a generator with double the inverter capacity does not apply.

I use a 5kW diesel generator limited to 3kW with my 16kW Deye and it works beautifully. When my loads are under 3kW the excess generator power goes to the batteries. When the loads exceed 3kW the batteries supplement the generator.

Thank you for the feedback. Can you tell me the brand of generator you have?

9 hours ago, Calvin said:

@JK84 has a Deye, which allow the inverter to limit the power it takes from the generator. That means that the old rule of needing a generator with double the inverter capacity does not apply.

I use a 5kW diesel generator limited to 3kW with my 16kW Deye and it works beautifully. When my loads are under 3kW the excess generator power goes to the batteries. When the loads exceed 3kW the batteries supplement the generator.

Thank you. Can you tell me the brand of generator you have and does it switch on automatically?

It is a Mac Afric 5kW Silent Diesel. It does not have auto-start.

See https://www.adendorff.co.za/mac-afric-6-5-kva-5-kw-standby-enclosed-type-diesel-generator-220v-single-phase

Note that this is a 3000rpm backup generator, fine for occasional use. (Mine runs less than 20 hours per year). If you expect frequent use you should consider a 1500rpm standby generator.