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Nicholas Wessels avatar image

Enabling Multi AC output 2 during grid outage

We have our system setup and have been using ESS for years now. We have critical loads on AC output 1 and non-critical loads on AC output 2 so that critical loads continue to receive power during grid outages. Today for example we have a scheduled power outage for the whole day.

We have more than sufficient PV/battery power (over 2500w) now to also power the AC output 2 loads (around 1200w).

Is there a way to manually enable AC output 2 during such times? If not this might be a nice feature to add to the ESS settings on the CCGX.


This is what is currently being used without anything on AC output 2:



I have manually plugged in a few items into the AC output 1 circuit to show what is actually available on PV:

Multiplus-IIESS
victron-nick.png (49.5 KiB)
victron2.png (48.5 KiB)
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3 Answers
NigelFXS avatar image

Update: since about a year now, all Multiplus II models -do- have a relay controlled AC2-output, and can be controlled just like all other models with a dual AC output.

old text:

This is not possible on the Multiplus II since the AC-Out2 is internally connected to AC-In. Connecting power to AC-Out2 (and hence AC-In) would be dangerous since this would feed power back into the grid during the outage.

A possible solution would be to install a change-over switch so that non-essential loads can be connected to the backup when needed.

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Thank you. Let me chat to my Victron installer and see what he can come up with.

Is the situation different on the Quattro? The block diagram for that unit suggests that AC-out-2 has a separate relay and could be software controlled in the desired way. (I don't believe there's currently an assistant for that, but maybe there could be...)

the MultiPlus and the Quattro have indeed a software controllable relay that can enable ACout2 even when in inverter mode.


The MultiPlus-II has no relay; ACout2 is hardwired onto the input.

byrons avatar image byrons mvader (Victron Energy) ♦♦ ·

So will programming the ACout 2 relay with say the programmable relay assistant override it switching off with mains failure ?

Geomz avatar image Geomz mvader (Victron Energy) ♦♦ ·

I'm curious about this too. Can an assistant be triggered (physically or logically) to enable AC2-out on a Quattro -with mains failure?

Yes very easy, and you can even use it to disconnect the ACout-2 when battery get's lower than a set voltage / SOC.

Just use the 'configurable relay' assistant, like in this example:

Awesome! Thanks @Boekel!

Wish I'd known that before crimping Feed 1 and 2 together <face palm> :)

Might have to just undo that and move "non-essential" loads back to AC2.

I don't really "have" to do it, but in that CYA mode where we lost mains and the heavy loads are still happily sucking the batteries down to 0 :D

Hi I tried this setting, but it sheds ac-2 out even if there is grid power available. Is there a way to set a setting to shed ac-2 at a set SOC only when no grid is available?

Geomz avatar image

What I did was crimp the wire-panel lead for AC1 and AC2 onto the same lug and attached that to AC1-out. Probably not ideal, but works and a quick win. My (old) system was setup with a similar "crucial" "non-crucial" config and the new system rendered that obsolete.

Makes for a thick wire-lug, but should be electrically safe as long as you have appropriate wiring and output rating limits.


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Martyn Duerden avatar image

Pahaps a contactor, 2 NO & 2 NC Coil on mains...

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