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cruisey1987 avatar image
cruisey1987 asked

Big Quattros and small backup generator?

Hi folks,

I just want to make sure that I have the right idea when it comes to backup generators

At some point I'm likely to upgrade my Solar with more panels and batteries and will either have a 15kVA Quattro or 2x 8kVA ones

I'd like to setup the system for a small backup generator in case there's a severe power cut

The idea would be to get a smallish generator (around 5kW) and run it when the battery SoC is low and I'm not getting enough power from the panels. The generator would then run for a number of hours to charge up the batteries when enough power to see my through the rest of the day

From looking at the generator FAQ, I'd be significantly below the recommended generator size. But I think that is designed for a situation where the generator needs to handle the full load of the house. In my case this wouldn't really be applicable, worst case I'd be running my heating system and some lights which should be within the generator output

I understand that I would need to limit the AC1 input power to ensure the generator isn't overloaded. Any other considerations I should think of?

Also, if I'm using a Cerbo GX, do I need to use the Generator relay on the Cerbo to remote start the generator? Is there any advantage or disadvantage to using the relays on the Quattro?

MultiPlus Quattro Inverter ChargerESSGenerator
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2 Answers
Kevin Windrem avatar image
Kevin Windrem answered ·

I don't see anything wrong with your plan. I have actually considered a similar setup.

I currently have a 5500 watt generator that handles most of the house loads during a grid failure. No solar - yet. I have a system that manages several of the heaviest loads to keep total power under the generator's maximum output. The generator has more than enough output to cover the daily watt-hour needs. Adding Quattros in a split phase configuration would allow higher peak power and also allow power to the home during the night when I'd shut down the generator ("quiet time").

While the Quattro does have a generator assistant, the one in a GX device has many more features including manual control. I would only use the Quattro generator control if the system did not include a GX device.

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cruisey1987 avatar image cruisey1987 commented ·
Thanks for the info, can't use split phase in Ireland but I'd probably just manage the loads manually so as to ensure the generator doesn't get overloaded if I'm ever in a situation where my batteries are low and the grid is down
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ahtrimble avatar image
ahtrimble answered ·

I use a 4kw inverter style-generator on my 5kw Quattro inverter (soon to be 2 x 5kw Quattro inverters). I limit the AC draw to 18 amps (2160 watts) to keep my generator to a healthy RPM and fuel consumption. Also, that easily powers the average 240w draw at the house. And allows for higher wattage devices to be used as needed, but limited...and to charge the batteries. I especially like running the gen at night when the power draw is at the 240w mark...and plenty leftover to charge the batteries.

So just match your gen output (AC input draw) to your normal usage + occasional higher needs...then add in how fast you want to charge your batteries. I would suggest keeping your genset at, or below, 50 - 70% of capacity.

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cruisey1987 avatar image cruisey1987 commented ·
Thanks, my base load is around 200W so the 5kW generator should be enough to cover it. Since my heating and cooking are electric, I think I just need to make sure the generator has enough capacity to run those in an emergency
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ahtrimble avatar image ahtrimble cruisey1987 commented ·
Good info! Just remember to make the inverter's AC draw setting appropriate to not overwork your genset. 50 - 70% of your genset capacity is a good range.
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