I have a Multiplus 48/5000 GX which is running completely off grid. I need more power. I could ditch the 48/5000 and buy 2 * Multiplus 6k5 to run in parallel, and then would also need a Cerbo GX. This would of course be expensive.
I’ve heard reports of people running the AC-OUT of a Multiplus into the AC-IN of a second Multiplus and then using Powerassist on the 2nd inverter. I know this is unsupported by Victron. So in my case I would buy a new 6k5 and then chain it with my existing 48/5000. I would only be chaining the 2 inverters, to get a combined power of around 10.5kw.
Is anyone able to comment on this (ideally someone who is actually doing it, or has tried to do it and had issues)?
Does it work? What are the drawbacks?
The set up will depend on battery abilities.
How are you setting that up?
Sorry, but in what regard?
This will be running off two 48v lifepo4 batteries running in parallel (16s EVE cells x 2, and 2 x 100A Overkill BMS).
(Or alternatively I could use MB56 cells to build a single battery of around 32kwh, using a single 200A or 300A BMS).
But how might this be relevant as reagards the inverters?
The common mistake is adding a second inverter sharing a battery bank and the poor battery bank can’t do it.
Are they sharing one bank or are you separating them?
They would be sharing the bank. Total capacity is around 30kwh. The combined 200A worth of BMS (100A x 2) should be able to support around a 10kw discharge rate.
So yes it will be slightly limited by BMS capacity, as the combined inverters could perhaps peak at 12 kw, but as long as I keep consumption under 10kw then I think that would be fine. Worst case I can upgrade the BMSs.
But all of this would also be exactly the same if the inverters were matched units running in parallel.
I’m specifically interested in whether anyone is successfully running Powerassist like like this? Any issues encountered etc.
As i have seen several people do it and hae read about a few on the forum. The problems start on the DC side- it needs to be robust if you are pushing the upper limit of the inverters power draw.
I have seen two variants:
- a shared bank
- stand alones further apart in ac set up.
When using ess on the second unit there is sometimes a weird oscillation.
But you are saying it is offgrid so i assume ESS assistant is not really in your programming?
When using both to charge the same bank - the second unit should have its charge disabled. And dont use weak ac unless you are experiencing issues.
Make sure the output of the second unit can do the 10kw. A further mistake is sizing 5kw on output and then, 5kw on the second inverter output when it should be for 10. Seems an elementary reminder but i will mention it as it has not occured to some that this is needed.
Yes no ESS is configured, as it’s an entirely off-grid setup and the batteries are (almost always) only charged by MPPT solar controllers.
Good point about disabling charging on the 2nd unit. The first unit might occasionally be hooked up to a generator but generator is only 2kw so can easily be handled by the first inverter’s charger.
When you talked about sizing 5kw on output, I am assuming you are talking about the AC output? So the first inverter AC-out needs to be wire big enough to handle 5kw and then the 2nd inverter’s AC-out wire (which then goes into the main consumer unit) would need to be sized for 10kw (obviously to be safe I’d put a big margin on these figures).
DC wiring from battery to each inverter I would assume just needs to be able to cope with the peak of each inverter - so likely larger wiring on the 6k5 cs the 48/5000. Is that what you meant?
Correct. Do install with the recommended size or larger.
Correct. One site we did some troubleshooting on for some reason mr assist was equipped with only a 5kw output sized wiring… Warm wiring and disappointment for the owner was soon corrected.