Marine charge current and shore power breaker control with CERBO GX

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blskevin asked Oct 28, '20

Marine charge current and shore power breaker control with CERBO GX

I have a recently installed Victron system consisting of two Multiplus units running in parallel, a BMV712 battery monitor and a CERBO GX.

The system runs wonderfully but I need to limit the charge current while the engines are running since I have a large engine driven alternator. I also need to limit the shore power breaker size setting when plugged into shore power.

I can perform both of these functions using Assistants in the Multiplus units, but that is not without challenges.

My first question is can I use a digital input on the CERBO GX to limit charge current in the multiplus units?

Can I use a digital input on the CERBO GX to change the shore power breaker size setting?

If the answer to those questions is No, then I have another couple of questions.

If I use an assistant on the Multiplus to use a digital input to limit charge current, does that assistant require a separate dry contact to create the same function in the slave multiplus? Or will the master Multiplus communicate with the slave multiplus to limit charge current from that one as well?

The other question is if I use an assistant on a multiplus to change the shore power breaker setting does this take away my ability to change the shore power setting from the CERBO GX display?

Thanks!, and here is a VRM screen shot of my system as configured.

Multiplus-II multiplus in parallel Assistants

ef4e9bc6-835f-4926-91ea-1f1478d7f0f0.jpeg (355.1 KiB)

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Answer 1 · 2020-10-28T06:32:44Z

bathnm answered · Oct 28, 2020 at 06:32 AM

Hi @blskevin, I can not answer the question regarding dual MultiPlus as I only have one.

You an use the temperature input on the Multi and an Assistant doc change the charge current. You want to use the Charge Current Control Assistant. This will let you change the charge current based on the voltage on a dry contact. It can use either the Aux Ports or Temp sensor input. I have not tried this yet, but plan to for the exact same reason. If on Shore power and I start the engine I do not want both charging.

If you do not have the VE.,Bus BMS in the system then you should be able to change the Shore Current Limit from within the Cerbo. See screen shot below. How this works with multiple Multi's installed I do not know, but a trawl of the manuals (VenusOS and MultiPlus) should advise as I have seen something as I went through my setup.

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Answer 2 · 2020-10-28T12:29:09Z

jwfrary answered · Oct 28, 2020 at 12:29 PM

If you have a digital multi control you can use the contact on the back of it to set the generator input current (I assume you have an AC generator and this is why you want to limit the charge current when the engines are running)

To be honest I would leave the multi to its own devices. When the Genny is running it will charge the batteries though absorption and equalisation which the alternator might not do depending on how smart it is. But if the ac load increases the multi automatically cuts the battery charge current anyway and then uses power assist if the load goes up that far.

If you haven't got a generator and its just the big alt on the main engines then, the short period your plugged in and running, wont be a problem and you can simply specify the current limit on the cerbo depending on the outlet your using.

Only the master needs the inputs, the slave will follow, but the charge current and input current are per multi, I.e if you set it to 12.5 amps you get 25 if you have 2 multis.

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Answer 3 · 2020-10-29T10:32:14Z

blskevin answered · Oct 29, 2020 at 10:32 AM

Thanks both of you!

I have not been able to find the ability to configure a input on the CERBO to limit charge current or change shore power size.

The information regarding the input on the multi in parallel is fantastic!

Here’s what I’ll do...

Wire input #1 to a relay tied to the main engine injection pump circuit at the key switch. This will trigger a assistant that reduces the charge current to 100 amps.

This allow the ability to run my generator while under way and not over current my batteries.

While in port I will manually change the shore power breaker size on the cerbo to match the shore power feed available at that location. I am not going to automate this through another assistant on the multi as I want to be able to set this using the CERBO display to match the local harbor.

If I use an assistant in the multi to do this I loose the ability to perform the same function manually using the CERBO display.

What I will also do is to wire input #2 to a shore power available relay. This will trigger a second charge current control assistant limiting charge current to 50 amps. This will provide protection against my forgetting to change the shore power breaker size to match the shore power, and tripping the shore power breaker after shore power outage while I am away from the boat.

Thanks again for all your help!

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bathnm commented · Oct 29, 2020 at 10:59 AM

You may find you can manage the charge rate with a single assistant. The "Charge Current Control" assistant uses a voltage value on the input to switch. So high voltage would be max charge and low voltage turn it off. Therefore when the engine is on, the voltage on the port is low and switches off. I am not sure if it will work with the port open circuit being less than 2v and port shorted the voltage is high, if it does the engine ignition just needs to open the relay/opto-coupler that is on the port.

You an also set this based on AC input port, so different based on AC1 and AC2 inputs.

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jwfrary commented · Oct 29, 2020 at 11:41 AM

https://www.victronenergy.com/live/ccgx:start#input_current-limiter_setting

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jwfrary jwfrary commented · Oct 29, 2020 at 11:47 AM

follow the link above to find input current limiter setting. It's also on the splash screen at the bottom of one of the Cerbo's main information screens.

So your alternator has a charge controller, external, balmar or something like that?

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blskevin jwfrary commented · Oct 29, 2020 at 01:59 PM

Yes I have a balmar multistage regulator, Thanks

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