control Multiplus relays via Venus OS

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schollex asked Jun 17, '23

control Multiplus relays via Venus OS

Hi,

I need to switch on/off a 230V heater depending on the internal cell temperature of my Pylontech batteries. For switching, I want to use a relay of my Multiplus II.
As far as I know, AC OUT2 can be used as well as AUX RELAY.

But my knowledge is that both relays can only be controlled via an Assistant.

But I need controlling within Venus OS on raspberry respectivly Node RED.

The only solution I figured out is to connect

# Relay 1 Pin 40 / GPIO 21
21 out relay_1

to AUX1 INPUT of the Multiplus and set up Assistants to drive the EXT RELAY depending on the AUX1 INPUT state. The, the relay can be controlled e.g. via Venus WebGUI or MQTT.

I haven't try so far. Can anybody confirm that this should work?

But there should be an easier way to controll the Multiplus-relays, especially without the need of an signal-wiring.

Bye, Alex

Relay

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Modifications Space

Node Red Space

Answer 1 · 2023-06-17T10:31:03Z

JohnC answered · Jun 17, 2023 at 10:31 AM

Yes, you can do this. Exactly in the way you describe, so a 'well done' for working it out yourself.

I'd usually run a signal wire pair for the contacts. This might seem clunky, but a lot of the smaller Victron kit come with Remote terminals for similar connections, so it's not uncommon in the Victron world to run wires.

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Answer 2 · 2023-06-17T15:16:11Z

schollex answered · Jun 17, 2023 at 03:16 PM

Hi John,
I did some measurement and testing.
The AUX-ports on Multiplus are powered with 5V. Thus if an AUX-port would be connected to an raspberry-pi GPIO, the pi would be destroyed.
I think a opto-isolator such as PC817 would solve this problem.

I did some manual testing. I wrote two assistants switching on/off ACOUT2 depending on the state of AUX1 respectivly AUX2.

Regardless which AUX is configured+closed/opened, ACOUT2 is switched as configured.

When AUX1 is configured+closed, the Multiplus immidiatly stops feeding-in exceeding PV-power to ACIN. After opening AUX1, the Multiplus restarts feeding in, but in an unbalanced way compared to my second Multiplus. The affected Multiplus feeds in less power than the unaffected Multiplus. After switching both MPs off/on. this unbalanced-problem is solved.

When configuring AUX2 instead of AUX1, all works fine.
There seems to be any alarm(?)-configuration on AUX1 I don't know.

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