Dave van Dongen avatar image

How to run a Multiplus with the batteries disconnected?

Replace Mastervolt Combi with Victron Multiplus to have better monitoring > Can the Multiplus run with the batteries disconnected?

A potential customer has a Vehicle2Grid system. It a living boat with a grid connection and solar panels and a smaller cruiser boat with battery and electric propulsion. Normally the small cruiser boat is next to the living boat and the battery is connected to the big living boat and grid and solar panels and is being used to maximise self-consumption. The system has Mastervolt lithium batteries on the small boat and some switching to connect the batteries to the electric propulsion and a pluggable cable connection to the big boat. On the big boat the battery cable is connected to a Mastervolt Combi battery inverter, which is also connected to the grid connection. On the AC output (micro grid of the big boat) are the solar panels, connected with a Mastervolt AC PV inverter. The Mastervolt Combi is 5000 VA/Watt. There is 4000 Wattpeak of PV panels and a 6000 Watt AC PV inverter. The Lithium batteries are 4 pieces of MLi Ultra 24/5000 (24 volt 180 Ah) in 48 volt configuration.

The system has a dashboard that is base on the Mastervolt monitoring software. But this is not maintained anymore and has all kinds of problems. This is the mean problem that needs to be fixed. It's also not really handy to select another battery usage mode (switch from Max. self consumption to Keeping batteries full, etc.). Also it runs on a laptop, which only purpose is to run this dashboard, which is a waste of power. Etc.

I suggested changing the Mastervolt Combi 5000 VA for a Victron Multiplus 5000 VA, so we could use the CCGX controller. Then we can have a good monitoring system that is being kept up-to-date and under active development. And it will be much easier to change battery usage mode. This can then also be done remotely, something that is not possible now. Also then they can get rid of the dedicated laptop and then will consume much less power with the CCGX. Also it will be easier to interface with all kinds of stuff, now and in the future.

The big question is: Can I use a Victron Multiplus 5000 for this. Because the system needs to run, also when the battery is disconnected, because this is something that normally the Multiplus doesn't like or even can't do??

I am not sure how this works in the current configuration with the Mastervolt Combi, because I was under the impression that this battery inverter also wouldn't like to run without the battery connected.

Or is there some "trick" I can use to keep the Multiplus running, when the battery is disconnected?

Any suggestions and help is welcome. I would really like to make this system (dashboard) working again with Victron equipment, also because this project would open doors to other interesting solar-battery-grid balancing projects that this customer is involved in.

Thanks in advance for any help! :-)

MultiPlus Quattro Inverter ChargerCCGX Color Control
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Some schematics of the current situation with the Mastervolt Combi 5000 that we want to replace with a Victron Multiplus 5000.
The question is what the behaviour would be of the Multiplus in this situation, when the work boat is gone sailing and the battery is therefor disconnected. What does the Multiplus do without a battery?

There's a few threads on the forum regarding this. I can't remember the key words for finding them off hand though.

Hello @kai , OK, thanks for your reply. I will try to look for it.

4 Answers
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Dave van Dongen

I'd prefer the unit being switched off when no battery is attached (yes you'll need a transfer switch than), but you can get away with using the two-signal bms to disable charge / discharge attempts and force the unit into passthru.

Make sure you have a current limiting device for connecting the battery (pre-charge) or you'll damage your connector.

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jesse avatar image
jesse answered ·

Battery inverter and inverter-chargers (a multiplus is basically a battery inverter)cannot start without battery. They were designed to work with battery power source.

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@Jesse, thanks for your reply. Yes, I know, hence my question how to work around this.

Dave van Dongen avatar image
Dave van Dongen answered ·

I have now also aked my Victron wholeseller and he says the Multiplus will work, in pass-through mode. I will get "low-battery" alarms and all, off course, but he says he tested it and is sure the Multiplus will just pass-through the AC. He is not sure about the Multiplus II, because he didn't test that yet.
Anyone else experience with this? To be sure.

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Tom avatar image
Tom answered ·

So hook up a small battery from a battery powered power tool to start up the Multiplus to place it in by pass mode to use the transfer switch to run off shore power. Be sure to turn charging off.

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