Planning off Grid - non parallel dual inverter, dual Cerbo GX question

Q&A and troubleshooting
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1

Hi all

I realise this subject area has been covered before but I’ve yet to find specifics that match. Apologies if there is overlap or repeat. I also understand there are a couple of sub-questions, but the items are so closely related, splitting them is counter productive.

In the planning phase for a system based on the following.

100% off grid 230V single phase, 48 VDC batts. Never will be a grid tie. No parallel operations. All Victron components except the battery bank (Pylontech US5000 x 4) and pv panels. Intent to provide generator feed for backup charge capability in the future.

I would like to use two inverters supplied by a single battery bank, each feeding a dedicated consumer unit (distribution board) i.e. loads inside the house split from loads outside the house. For redundancy purposes I am discounting products such as Easy Solar with internal MPPT. I prefer separate units where possible.

Some confusion exists. Questions based on dual inverter capability, avoiding wasted functions by buying two inverter chargers and to allow different inverter sizes. For clarity house inverter being INV1 and the exterior INV2.

1). Assume INV1 is a MultiPlus II providing the ability to connect a generator.
Could INV2 be a straight inverter i.e RS Smart 48V 6000 or similar?
Do INV1 & INV2 need to cross talk?
Does INV2 need to talk to the batteries?

3). The Cerbo GX manual shows config data for single, parallel, split- and three-phase VE.Bus systems. The only reference I see for two individual inverters to be fully monitored is via 2 seperate Cerbos. This being the case, for system control, do the two Cerbos interlink with a master/slave setup?

Clearly, I have some confusion here. Bottom line. I would like to run two inverters, one being an inverter/charger, both different output sizes, one at the 8000VA level capable of running the likes of water pumps (high inrush) and one smaller.

Thanks for your attention.

2

Hi.
I’m a little confused too. We sometimes see this dilemma with people expanding an existing system, but rarely when planning a new one.

Why not just have a single, say 8000 Multiplus with 2x AC outlets, and separate those AC outlets to the distribution boards? Multi has ACOut1 for your house, and a switchable ACOut2 for your outside. That switching can be set up in a number of ways, depends on what you want with it.

Then everything could be made to actually work. From the same BMS-control batteries, two independent units is asking for heartache.

Maybe you have good reasons, but we’d need to know them. I’m offgrid with Pylons too, but would never do that. Never…

3

Thanks for the reply. To be honest I hadn’t thought of that.

The property came with an old very poor solar system - soon after moving in the single inverter failed. Replacement took over a week for delivery (it’s my location). Based on that my thinking was dual inverters, automatically providing a hot spare.

The second reason was pv panel and component location. The most secure/sunlit position is equidistant between house and external loads hence originally thinking of the split.

I had toyed with splitting the battery bank but that is in effect two full systems with cost implications.

In the config you suggest - would AC2 have to be switchable or is that in effect a load protection?

4

Those reasons don’t convince me I’m afraid. Too much grief beckons for something that should run smoooth as silk. If you want a spare, keep a cheapy in the shed for that emergency that will probably never happen. I don’t keep a spare for my 8yo Multi, hey. Reliable they are…

You don’t have to use ACOut2, just saying you could. It’s ON by default when ACIN is ON (genset?), but could be set up to apply on various conditions, like Load, batt SOC, time based, etc.

5

You’ve given me good food for thought. Suspect I will ditch my ideas and follow up on yours.
Appreciate your time. Thanks.