Multiplus or Quattro - Prefer solar vs shore power

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overtaxed asked May 11, '23

Multiplus or Quattro - Prefer solar vs shore power

Looking at adding a lot of solar to my RV (1600 watts or so) and moving to Victron components. I keep my RV at home connected to 50A power. I keep the AC and heat (heat pump) on (85/45) to keep things from getting to hot/wet or cold/frozen in the RV.

The electric at my barn is commercial rate (expensive) and I'd like to see if there's some way, on either a MultiplusII or a Quattro to "prefer" solar over shore power. Basically, if my batteries are full, I'd like the inverter to do PowerAssist for all the power coming in from solar and reduce the consumption on the grid, similar to how grid tied solar works when installed on your home. If the demand exceeds what the solar panels are producing, then I'd like to pull from shore power to make up the shortfall in solar production.

Any way to program either device to do this automatically? Expressed as if/then:

1) If batteries are full

2) Then take any solar power created, invert it and do PowerAssist with the excess.

powerassist shorepower

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Modifications Space

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Answer 1 · 2023-05-11T13:21:46Z

matt1309 answered · May 11, 2023 at 01:21 PM

I believe ESS assistant adds those features, if I'm understanding correctly.

ESS Quick Installation Guide [Victron Energy]

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derrick thomas commented · May 11, 2023 at 03:13 PM

Victron specifically states NOT to use ESS for mobile applications. That being said, it has been done by a few people. The simple safe solution is probably going to be using node red to ignore ac input under certain conditions, or dynamically change the input current limit based on certain parameters.

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overtaxed derrick thomas commented · May 11, 2023 at 04:01 PM

"dynamically change the input current limit based on certain parameters."

That's exactly the functionality I want. If the batteries are full and solar is producing, change the input current limit to "Output current - Solar current" so that power assist will kick in and use that solar power rather than waste it. As I understand it, if you have 2000W of solar, full batteries and you're plugged in, that 2000W of generated energy isn't used at all, it's just "waste".

Honestly, this is functionality that should be as simple as a check mark in the configuration, "Limit grid consumption" or something like that. The capability is there and the logic is dead simple.

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Answer 2 · 2023-05-11T16:10:39Z

overtaxed answered · May 11, 2023 at 04:10 PM

Thanks for the guidance, taking a look, it seems that I want is to configure "self-consumption hub 1":

https://www.victronenergy.com/live/assistants:self_consumption_hub-1

With "Connected to mains, no feedback" as my policy. Is this something that's part of the Multiplus (or Quattro), or something that needs to be added separately?

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Answer 3 · 2023-05-12T08:58:08Z

JohnC answered · May 12, 2023 at 08:58 AM

Hi @Overtaxed

There's a number of ways to do this, but what you choose may be dependent on the kit you have.

A really simple one is to just set the Multi/Quattro battery charge settings a smidgen (or a lot, depends on your batteries) lower than the solar mppt's. So the solar will have priority by way of Voltage alone.

Or if you want to delve deeper into Assistants, then you could 'Ignore AC' under conditions like high batt SOC, so giving solar room in the batts to fill as well. You need to plan this somewhat, and purchase what you need for full access to all the features.

As mentioned, don't use ESS. It's really for power exporters, not RVs. Imagine having live male pins on your power plug when you disconnect it..

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Answer 4 · 2023-05-12T10:27:39Z

overtaxed answered · May 12, 2023 at 10:27 AM

Thank you John. Could an assistant say something like "At high battery SOC, turn down the AC current limit from 50A down to 5A" to get the Multi/Quattro to go into PowerAssist? That's seems like it would do what I want, not perfectly, but pretty close. It's not so much avoiding the charging energy consumption I want to limit as it is using the solar production to power the RV when the batteries are full.

It's unfortunate ESS isn't supported in this configuration, the self consumption hub 1 seems to provide exactly the functionality that I'd like to have. It's surprising that there's nobody who makes a "box" that you can connect between your RV and your shore power that prevents the "hot male" problem. Similar to how grid tied home solar works, when the grid goes down, there's an immediate disconnect of the backfeed into the grid to prevent pushing power into the transformers and energizing lines that are supposed to be dead. It feels like a few relays/diodes you'd be able to build something like that pretty easily.

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JohnC ♦ commented · May 12, 2023 at 12:06 PM

@Overtaxed

That example/request is likely possible with a workaround. I won't go there just yet, as this is unusual and there are probably better ways.

Whatever current limit you set will be passed through to loads as priority, no matter what solar is producing. No point mucking about. If you don't want the grid to serve loads while solar is producing, then turn it off. Then bring it back on when it suits, like when batt SOC and/or V drops. So your batts will see a little current flow. I call it 'exercise', a little heavy breathing. A bit of work may even benefit them.

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overtaxed JohnC ♦ commented · May 12, 2023 at 12:42 PM

Adjusting the current limit would work, I just see myself forgetting to do it. The use case for this is my RV sitting at home, connected to 50A, with the ACs left on to keep the rig from getting too hot (or cold, heat pump ACs). I do that today with my setup, but, of course, it pulls all the power from the 50A shore and none from batteries or solar. My solar panels basically spend almost 100% of their time sitting idle in the sun. With the 200W of solar I have today, no big deal. But I'm considering going up to ~1500-2000W of solar and wasting all that power 99% of the time seems silly. I could just not plug in at at home, but then the batteries would cycle every night, which wouldn't be great for them, which is why I'd like to, once at 100% SOC, just take all the solar power and PowerAssist with it. No solar, no PowerAssist (just use shore power); but if solar is making power, use that before pulling anything from shore power.

The other complication is that the inverter can't support all the loads, if 2 of the ACs start at once, for example, without shore power connected, the inverter will likely trip.

Please, "go there", I'd like to get some better ideas on how to configure this to maximize the consumption of solar if at all possible. :) And thank you!

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JohnC ♦ overtaxed commented · May 12, 2023 at 02:22 PM

@Overtaxed

Firstly (gotta say it), you shouldn't have more loads turned on than your inverter can handle. Victron kit can genuinely handle reasonable overload, but best not design that into it.

Ok, I'll 'go there' with the Assistants. Without research though. There's an Input Current Limit Control Assistant, which can step that, but requires an external (low V) signal from (say) Aux1 port. Programmable Relay Assts (to apply your switching logic) can drive an output relay (say K1). So a wire pair across from K1 to Aux1 should work, Aux1 will pull-up the V when open to enable the change. Clunky, but should work fine.

Given you don't have this kit yet, you'd need to make sure that what you do buy has this stuff onboard, some of the small gear may not. And I'd also add in a Smartshunt for a good SOC source, and a GX device for the full lounge-chair access treatment.

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Answer 5 · 2023-05-12T14:38:33Z

derrick thomas answered · May 12, 2023 at 02:38 PM

The easiest way to implement what you are looking for really would be node red. You could also incorporate some dynamic controls through the node red dashboard so you can make changes on the fly without ever having to mess with assistants.

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