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alaskannoob asked

Two Victron inverters *not in parallel* same battery bank - issues?

Off grid: If I had two Multiplus II 48/8000 (not in parallel since they cannot operate in parallel) that were connected to the same battery bank, with only one Multiplus II connected to a generator for charging the battery bank, but that supplied two separate AC outputs to two separate load panels through two separate sets of cables, would the Cerbo GX have any issues with this? Would the Victron Remote graphic show two inverters pulling power from, and one inverter sometimes charging, the same battery bank?

Most importantly, could I set it somehow so that the sum current draw from the batteries by the two inverters would not exceed a certain current?

My batteries can supply 800A. But the cables are limited to only drawing 400A. I would want one inverter to be able to pull 300A while the other inverter drew 100A. As such, I want to avoid limiting both inverters to drawing 200A each. Can the Cerbo GX orchestrate this sum total limit of current draw from two inverters that are not operating in parallel?

Multiplus-II
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JohnC answered ·

Hi @AlaskanNoob

The GX can only handle one inverter (or group of synced units) as it's main reference. I think any extra can be included in the displays if the VE.Bus cable is connected to the GX via the MK3/usb dongle, but the overall outcome I can't say how suitable that might be.

Re limiting your battery output when serving ac loads, that's not possible directly. If it were, all the kit could do is trip all your ac loads, and I suspect you wouldn't want that. So it's up to you to control what ac you switch in. Limiting a dc cable to a certain A is a mushy thing anyway, short-term vs continuous rating. Like the starter circuit on a vehicle is never rated for continuous draw, but subjected to very much more for short periods.

You say in another post that Victron is helping you change out these units anyway. That's a great outcome.

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alaskannoob avatar image alaskannoob commented ·
It is great of Victron to do that.


At this point I am thinking we will keep one 48/8000 and get a 48/15000. Both connected to the same battery bank. The 48/15000 will have the generator connected to it so that it can charge the batteries. It will use our Cerbo GX and will send power to one part of the property to an Autotransformer.

We'll get a second Autotransformer for the 48/8000, skip a second Cerbo GX for it since it won't really tell us much, and wire it to the AutoTransformer on a second part of the property.

We won't be able to *see* the 48/8000 on Victron Remote, and it won't even show up as an AC load. But I wonder how a large draw on the batteries from the 48/8000 will look to the Cerbo GX connected to the 48/15000? Or maybe it just won't care. I just wonder if there will be any unintended consequences to doing it this way.

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JohnC avatar image JohnC ♦ alaskannoob commented ·
@AlaskanNoob

The GX won't 'care' as such, the figures just won't balance. But there's a 'Has DC' option which can quantify the imbalance, and you may find that enough. That MK3 thing might work, and there's always the option of adding in a Smartshunt and allocating the 8000 as a dc load.

I'd grab an MK3 for sure if your 8000 is standalone, and thus no VRM to help with fw updates and setting changes.

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alaskannoob avatar image alaskannoob JohnC ♦ commented ·

Thanks for that info, much appreciated. We have the MK3 and have used it for upgrading firmware. I guess the thought with using it would be that it might allow tracking the 48/8000 as a "Has DC" load by connecting one end of it into the VE.BUS of the 48/8000 and the USB end into the Cerbo GX?

The SmartShunt is an interesting idea although we'd have to re-wire things to make that work. We have 4 sets of 2 US5000s in parallel, with a total of 4 positive and 4 negative cables from the 4 sets of batteries going into the Lynx Distributors for fuse protection. Instead of connecting to the Lynx from the non-fused bus bar portions that stick out. We'd have to re-work that to use a SmartShunt which is something we'll keep in mind for the future. Not that it's vital to track the 48/8000 load really.

I wonder if I could instead use a Lynx Shunt and wire the 48/8000 into that to get some data through the VE.CAN, while the BMS from the batteries communicates with the Cerbo through the VE.CAN as well. My batteries will send their info to the Cerbo (Pylontech), so maybe the Lynx Shunt measurements will just show info about the 48/8000 without messing up the battery readings. Worth looking into.

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