question

hibe avatar image
hibe asked

Subtracting AC2 out load from main to not drain the battery

I'm currently designing my Victron setup (grid connected using multiplus-II).

I want to leverage the AC2 out for things that are really not critical. Given that these are not critical I also don't want these loads to deplete my battery in any situation. They're fine to run when the grid is connected and also fine to consume excess solar, but they should never be taken into consideration to take any power from the battery for this.

In the documentation it seems that there's no measurement for AC1 out and also not for AC2 out, there's only measurement on AC in it seems. Is it possible to create a setup in which the multiplus will subtract the power pulled by the AC2 out loads from the load from AC1, so that it doesn't supply the AC2 loads with power from the battery at all?

Multiplus-II
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Fideri avatar image
Fideri answered ·

@Hibe

I could be wrong but as I understand it, you can't achieve that directly. But it can be achieved indirectly, if you can get your hands dirty.

From my research, you can't separate AC out 1 loads from AC out 2 loads without additional hardware. The inverter always reports both combined.

There are two possibilities. The expensive one is to fit a meter on AC out 2 and make the calculations. I don't how you then control AC out 2.

The cheaper option which I use is to connect my GX device to the aux port of my inverter and use the inverter's assistant and Node Red to control AC out 2. The logic is to provide power to AC out 2 only when my SOC (or combined loads) is above a personalised level. I'm simplifying but you get the picture. This always uses the amount of battery power I set (say 1%) but it works.

Fideri

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celts88 avatar image
celts88 answered ·

Sorry no help for yourself but for me it's the opposite way. I've a fair amount of battery (1070Ah) & solar (2430kW) so would want AC2 out to be able to work without the 240V in requirement, i.e. run both AC1 & AC2 from the batteries.

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Kevin Windrem avatar image
Kevin Windrem answered ·

The way the system works by default is the AC 2 out will disconnect if the AC input drops. Because of this, you should never draw battery for the AC 2 out loads. You will not see an independent power measurement but I think the system will work the way you wish it to.

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Fideri avatar image Fideri commented ·
@Kevin Windrem

I agree with you but clarification of 2 scenarios would help:

1. What happens to AC out 2 when the grid is insufficient and you have BatteryAssist enabled?

2. What happens to AC out 2 when you lose grid, whether BatteryAssist is enabled or not?

F.

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Kevin Windrem avatar image Kevin Windrem Fideri commented ·
Assist will kick in to help supply AC 2 out loads. Assist is a great help for short term power needs but I would not design a system to rely on it for long term power needs.


AC 2 out will turn off if you loose the grid.

These are default behaviors but the Multi can be programmed in different ways via "assistants". However, there is still no way to change behavior based on AC 1 vs AC 2 load power. (The AC output power is measured before AC 1 and AC 2 outputs are split.)

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Fideri avatar image Fideri Kevin Windrem commented ·
Understood.
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hibe avatar image hibe Kevin Windrem commented ·

The more I think about it the more it makes sense for me to have a separate power measurement device on AC out 2. Hopefully I can make the multiplus take this into account and not drain the battery ever for AC out 2 (E.g. my electric element which is a backup for my heatpump, and my car charger).

I'm fine with these not working on a grid failure. but they should never be supplied surplus from a battery.

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celts88 avatar image celts88 hibe commented ·
I'm no expert and just surmising here, but if you had a Lynx shunt could this be set up to talk to the Multiplus via a Cerbo so that when the battery charge goes below a certain amount as measured by the Lynx Shunt then it cuts off AC2 via the Multiplus?


I may be way off the mark here, sorry if giving a wrong answer.

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Kevin Windrem avatar image Kevin Windrem hibe commented ·
Look into running node-red on a Cerbo, Ekrano, etc. With it, you can extend the logic. You'd probably also need to meter AC 2 loads and connect that to the GX device.

There is no way to throttle the inverter's power generation though. If for example, AC 1 loads are 1000 watts and AC 2 loads are 2000 watts and your grid limit is set to 2500 watts, the Multi by default would add 500 watts from the battery. The only way to prevent taking energy from the battery would be to disconnect AC 2 loads

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lifeingalicia avatar image
lifeingalicia answered ·

If you dont want to use bat and dont need grid failure for loads simply bypass the multi. Any excess will first be consumed before the grid meter the rest will be pushed into the grid.

If you need to measure this use an external three phase meter and loop the lines accordingly.

L1 grid L2 Multi L3 bypass load.

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Alexandra avatar image
Alexandra answered ·
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