How to properly make use of multiplus & smartsolar as backup power at home

DIY
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1

So, I have a Smartsolar 150/45, SmartShunt, temp probe, and Cerbo GX in operation for a bit - all works well keeping a 200AH battery charged.

The only load is some isolated computers and networking gear plugged into a dumb inverter with a transfer relay, so that the gear is all powered directly off AC, and if AC fails the load runs on the inverter. This is all fine, and on sunny days I sometimes disconnect the AC so it can all run off solar+battery for a few hours until the sun goes down.

Now I’ve just picked up a MultiPlus 12/1200/50 this afternoon to experiment with, and obviously it’s much more complex. I’ve use VEConfig to set the basic battery parameters etc but it seems like I should be able to get close to what I’ve been doing with the old system but automated, rather than the out of the box config which would just run everything off the grid all the time.

There won’t be any connection to the house wiring except for AC input, and there absolutely can’t be any attempt to backfeed AC to the grid. This is effectively a portable system that powers a few isolated devices on a power strip.

Ideally I’d like to have it run the load off the inverter when PV is approximately sufficient to cover the load, switch to passing grid AC directly through to the load when it’s not, and only ever charge from the grid if battery SOC gets quite low, like 60% or whatever.

I’ve experiment with both ESS and the self-consumption hub assistant but I’m not confident in what they’re doing. For instance with self-consumption hub right now set to “Connected to mains, no feedback” the battery SOC is 100%, the charger is in Float, the sun is shining brightly, but the charger is still drawing the same amount of power off the grid that it’s feeding to the load, though it seems to be feeding the load from inverter rather than passing through (is that even a thing with these?)

With ESS the amount of configuration was daunting and I wasn’t confident it would never try to backfeed the grid so I didn’t mess with it too much.

There’s really a lot of conflicting and possibly outdated discussion about this stuff online and it’s hard to tell whom to trust so I’m really just looking for “Oh, the current, correct way to do it is XYZ” or “You can’t really do that with this device” or “What you think you want is not what you really want” here.

Thanks for any input!

2

The manuals are the best place to start.

You need a GX device to use ESS, so this is possibly why it is not working how you expect. Do you have one?

(1. ESS introduction & features)"
What is the minimum requirement for ESS?

Summary

There must be at least one inverter/charger (MultiPlus/Quattro) and one GX device such as the Cerbo GX or Ekrano GX in the system.

If not there are two methods available to you
One is ac ignore.
It is easier to program with vIctron connect not ve config.

The second method is solar wind priority it is designed to be used in mobile applications but does have the not allowed to feedback to grid built in. The battery will be fed by solar but ac loads directly from grid.

3

Yes, I have a Cerbo GX - i probably typed far too many words up above. I’ve cobbled together a sort of solution by using programmable relay assistants to use the “temperature sense” input on the 12/1200/50 to instead control Ignore AC, and then connecting one of the GX’s relay outputs to it. So i can set up the GX to treat it like a “Generator” and turn charging on and off based on battery SOC. It’s good enough, I guess, but it takes too much manual fiddling, particularly if i want it to just pass through AC to the loads without charging the batteries so they can get charged by solar in the morning.

4

Cerbo GX in the first sentance. I am either blind. Or forgetful :person_facepalming: apologies.

With ESS you can set a minimum state of charge in case of grid faliure i.e. your 60% and then set up scheduled charge to make sure the system uses PV only during certain hours of the day. Or makes sure a target soc is reached at a certain time.

5

I suppose I should look at ESS again, it seems like the most supported approach. It seemed there was some reason I couldn’t use it though, perhaps because it wasn’t possible to guarantee it wouldn’t attempt feeding power back to the grid, which isn’t an option here.

6

For sites that aren’t allowed to feed to the grid we use grid set point and always draw a few watts from grid. Sometimes it needs to be tuned abit depends on the amount of reactive power in the system. Many of my sites are set to 25 or 50 watts.

It is also covered in the manual.

7

Yeah, this all seems pretty reasonable. I think what I will end up wanting is ESS with a high minimum SOC to reserve a lot of capacity to cover power failures. I think the issue that put me off it before is that ESS doesn’t seem to be aware of DC loads at all, only AC loads fed by the Multiplus.

So for instance just a bit ago I set the min SOC to 90% and it happily ran the battery down 90% and then kept it there. But then I turned on a 10 amp DC load and its just discharging the battery at 10A, and it’s down to 87% SOC, well below my set min, and still falling.

There is a SmartShunt in the system so it knows the actual DC draw and showing the decreasing SOC so it’s not like it doesn’t know there’s a DC load, so I’m not sure what’s going on with that. I guess most people don’t use significant DC loads so maybe it doesn’t come up much.

8

This is more used in mobile set up where the solar wind priority helps with this.

Cant be used in combination with ess though.