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Stacked MultiPlus Questions

I currently have a single Multiplus 12/3000 on my boat and I'm interested in adding a second to give me 240 amps of charging, 6000 watts of inverter, and redundancy in the event that one fails. This seems pretty straightforward, but I have two concerns.

1. What happens if one inverter fails? It seems as if the whole system goes down until the functioning MultiPlus is reprogrammed to operate as a single unit. Is this true? If so, stacked Multis would actually halve the reliability of the system, rather than provide redundancy.

2. Are both Multis running all the time, wasting battery power, even when the total load on the system is only a few hundred watts? Or does the slave only power on when demand exceeds what the master can provide?

Thanks!

MultiPlus Quattro Inverter Charger
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3 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

1. Yes if you wire and program them to work in parallel then the whole system will shut down if one unit fails and you have to reset the working unit to stand-alone mode.
But if you wire them separate at the output (each supplies different circuits) they will work independently, so if one fails the other will remain on.
But you will lose the ability to draw 6000VA permanently at one circuit.

2. Parallel or not, if the units are switched on each will need 25-35W of idle power.

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Matthias, thanks for your answer. Can you elaborate on the charging 2x120A issue that gmd mentions below? That's a major reason for me adding a second Multi. I have a 1400 amp hour battery bank, so when it's down at 50% I'm hoping to be able to charge much faster than 120A. Thanks!

My issue with the charging was the setting in Configure and the Input current limit.

Set Charge to 120 in Configure and at 15+ Amp input limit then I have seen 180+ Amp charge current.

regards

Gmd


gmd avatar image
gmd answered ·

There are lots of shortcomings with the Multiplus for "advanced" recreational applications. I have similar issues but have a caravan and not a boat.

I wanted the same: Redundancy, Flexibility, low power consumption. Not really working that way.

The multi is easy enough to reprogram from parallel to single, however as you describe it would be more convenient if it would work a bit like assist. Only fire up when needed. The idle current is too high for two units, that also applies for the BlueSolar.

Another shortcoming is when on AC In. You have to run the inverter/charger and cannot just use a transfer switch. I understand the logic for the UPS/Assist functionality, however it would be good to have a "passiv" transfer switch.

I have solved that by using an 1800W Xantrex for the circuits I need on permanently, e.g. fridge. The Xantrex has a transfer switch, which works with inverter off. The Xantrex is real basic compared to the Victron units, but does it's job and can be passive when switched off. The circuits connected to the Multies are powered using a manual changeover switch. The Multies stay off, batteries are charged by solar if required.

The Multies stay off when not needed. Same applies to the Solar chargers. When set to off they should not each that much power. For recreational setups the idle power is too high. One can do that with 20mA or less. I separate the solar chargers from the battery with a relais when not needed (at night).

Generally I am still happy with the Victron products, besides a few things which could be done better, but I guess recreational use is not really a priority for Victron.

I still have to find out how to push the charge current to 2x120A. I only get 120A +- a few Amp even when my batteries are down enough.

regards

Gmd





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skykay avatar image
skykay answered ·

That is a question I would also like to be answered. In Germany with 3 phases and 3 multiplus can 2 use aes to save power?

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AES is not available in parallel or 3-phase systems.
https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems
But in a 3-phase system it is unusual that only one phase is loaded.


AES ist im parallel bzw. 3-Phasen Betrieb nicht möglich.
Aber es ist auch unüblich, das in einem 3-phasigen System nur eine Phase belastet ist.