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852 avatar image
852 asked

Connecting small portable generator to Quattro 15kVA inverter - can I use AC Input 1?

Hi. I am living on a boat with an entirely off-grid system. Equipment:


9kW solar

30kWh lithium batteries

3 x MPPT 250/85

Quattro 15kVA inverter charger

Color Control GX

Honda 2.2kW portable generator

NO shore power

NOT wishing to have automatic generator start-stop


95+% of my power needs are being provided by solar. I just want to occasionally run the small portable generator in cases of prolonged lack of sun in order to top up the batteries, i.e. trickle charge of approx 1400W. This is a simple manual process, e.g. I start the generator and leave it running for, say, 3 hours to top up batteries by 4kWh - not automatic start/stop based on battery SOC.

The generator connects fine. The issue is that the generator is immediately overloaded due to either of:

1. The batteries demanding more charge than the generator can provide (generator capacity is only 2.2kW).

2. A heavy draw AC item becoming active, e.g. the water heater switching on.

I understand why (small generator cannot handle big loads) and am aware of a workaround via the settings in CCGX to limit the overall charge current such that I have been able to use the generator to charge the batteries whilst avoid it being overloaded. However.. it is a very tedious process that requires constant monitoring/adjusting of the limit in the presence of varying additional charge supply (i.e sunshine) and it does not solve the second problem, that when a heavy AC load is introduced it immediately overloads the generator which then cuts out in order to save itself, therefore I have to disconnect all such potential loads in advance.

I understand that the proper way to solve the issue is to set up an upper charge limit on the relevant AC Input such that the generator can never be asked to supply more than that amount. In my case I wish to set it at 6A. 6x230 = 1380W, so comfortably within the generator's 2200W capacity.

I see online that the recommended set-up for two AC input sources is to have the generator as Input 1 and shore/grid power as Input 2. However, the guys who installed my system did it the other way around: shore power is Input 1 and the generator is Input 2.

My question is: In my case does the allocation as to Input 1/Input 2 actually matter? It seems to me that it should not. My understanding is that the only important difference between AC Inputs 1 & 2 is that Input 1 has the higher status such that when both AC Inputs are active then AC Input is given priority, i.e. if both shore and generator power are available then under conventional set-up the inverter would use the generator whereas in my current set-up it would use the shore.

Please note that whilst I do have a connection set up for shore power (currently AC Input 1) this is not actually live. My boat is on a mooring a long way from any shore power. The connection is only there as an option in case of one day the boat being in a marina or at a boatyard for maintenance. As it stands currently the only actual AC input source I have is the generator. Therefore now (and for the foreseeable future) there can never be the situation of both AC Inputs being active.

Obviously I would prefer to stick with the current set-up (AC Input 1 as shore and AC Input 2 as generator) rather than have to re-wire the connections to the inverter. If that is deemed to be ok then I would simply set the current limit for AC Input 2 as 6A. Please let me know if there are any issues that I haven't considered.

Many thanks in advance for your advice.

Generator
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2 Answers
JohnC avatar image
JohnC answered ·

Hi @852

You could use either ac input. (good news, but it mostly ends there).

There's a minimum A limit applicable, and for a 48/15000/200 it's 14.5A (I looked it up). That applies while you have PowerAssist enabled, but to turn that off likely wouldn't suit your loads. And if you have a VE.Bus bms, then it won't work at all.

There's some discussion of it here, see Section 3.1: https://www.victronenergy.com/live/ccgx:start

It shouldn't be influenced by other chargers, only if you have something set to do that

Maybe you could workaround it by minimizing your loads, and turning off PowerAssist. But really it's a classic case of mismatched kit.




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852 avatar image
852 answered ·

Thank you @JohnC, much appreciated.

I had not been aware of the PowerAssist minimum input current issue. Annoying.. So I guess for now I'll have to use the following workaround:

Leave generator as AC Input 2.

Before running the generator disable all potential heavy AC loads, e.g. automatic water heater.

Ensure the maximum combination of background AC loads (lights/fridge/gadgets) cannot exceed the generator's 2200W capacity (in fact for safety only around 80% of this, say 1800W).

Via CCGX Settings enable Limit Charge Current and set this to somewhere in range 30-70A. The exact choice of A will depend on 1) the AC loads that are running (typical constant draw is 200-300W) and 2) the solar supply (in daylight hours the panels will be providing variable charge depending on sun conditions). Basically, the higher the AC loads and the higher the PV supply, the higher I can set the Limit Charge Current.

Please let me know whether you agree with this workaround.

Secondly, as a longer-term solution I'm thinking perhaps simplest is to buy a second (identical) Honda 2.2kW generator. These can be paralleled, meaning 4.4kW total capacity and that would then meet the 14.5A (14.5@230=3335W) minimum input requirement for PowerAssist. If so then I would again leave the generator as being AC Input 2 and then set the maximum current limit for AC Input 2 as, say, 15A, so 78% of the combined generators' capacity.

Please let me know whether this sounds sensible.

Many thanks again.


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JohnC avatar image JohnC ♦ commented ·

Yeh, I can't quite get my head around what you're suggesting there. Seems like a watch'n'control thing, you could try..

I use a genny too, not often though, just when needed in winter's short, cloudy days. VRM sez 2% of my total generation p/a, and your 9kW solar should get you a long way there.

I have a 'philosophy' though when running it, and that's to get max batt charge value. So I don't complicate things by running it anytime, and leave that til solar is done. By then my heavy loads are finished, and almost all of the genny load will go to the batts.

I appreciate your setup is different, but your aims are likely the same. Like a constant 1800W from the genny while it's running to get max value, it'll serve your loads first, then boost your batts with the remainder. And you should be able to get there by switching off PowerAssist. No reason you shouldn't be able to do that concurrently with Li batts and pv charger, but your loads will need restricting to 1800W (including spikes the genny can't handle).

Hope this makes sense..



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