Modest generator size for off grid battery top up

Q&A and troubleshooting
,
1

I have a small off grid setup:

2.3kw solar / multiplus ii 48/8k / 15.5kwh storage

This has been more than sufficient for my modest needs through spring and summer but now the bad weather and shorter days (mid-wales, UK) are creeping in, I’m going to need a generator to top up the battery.

I know Victron recommends oversizing the Genny based on inverter size but budget wise that’s out of reach for me. My question is, can I use a smaller generator (looking at a 6kva diesel) but just with the intent if using this to top up the battery when it is low?

I’ll be increasing the solar in due course but my immediate need is to have on demand power. Any advice much appreciated.

2

So another approach would be:

How much load does the household need and how many amps do you want to charge at the same time?

The sum + reserve * efficiency would be the generator’s output.

If someone then turns on the kettle, the system switches to Power Assist :wink:
In other words, there should not be such large load fluctuations.

3

Thank you, I think that’s what I’m seeking confirmation of.

The load is generally tiny (<2kw) currently and even as I expand the property can be managed when necessary.

So demand wise, I’m comfortable that a 6kva generator will be sufficient for load and charging needs. I just wondered if there were other considerations. I know I can set the multiplus to only draw up to a specified load which is handy.

4

But be careful:

The house network is supplied directly from the generator when it is in operation. This means that if it has a poor sine wave or voltage fluctuations (=too cheap :wink: , there may be problems with the connected devices.

The MP2 has a minimum configurable input current limit.

An alternative would be an AC/DC charger that charges the battery directly. This is also discussed here quite often.