In series the amps stay the same. So 15A is the answer. You did say in series…
Your picture shows a 12V setup. If the inverter is 12V, then the batteries go in parallel. Then the amps should be 60… although I would feel uneasy with that. These Omni’s have a way of developing bad cells, and in parallel, once one of them develops a bad cell, the other batteries will get more of that 60A. In other words, you should not count on it dividing evenly into 15A each in a parallel setup…
The default VE.Configure settings are otherwise fine. Turn on “stop after excessive bulk”, so that it stops charging if the battery can’t reach absorption (which generally means something is wrong with it).
Can you share your experience with this deive? I am especially interested in the noise level this device is producing under mid (500W) to high loads (1.5kW+)?
Is it affordable to stay in a living area?
I noticed threads in different forums (inc. Victron’s) that some users are complaining from some excessive noise, that comes not only by the fans.
Can this be compared to the MP II 48/5000VA model?
I never had MPII 3K. My first device is MPII 5K, and to answer you question, there is hardly any noise to no noise at all when the MPII is inverting 500W…and then also minimum to none for up to 1kW…once it goes above that the fan turns on.
My factory fan (Jamicon JF1238B2HR-R) was generating too much noise for me so I opened the unit up and replaced the factory fan with the Noctua NF-F12 IndustrialPPC 24V-3000 Q100 fan. This mitigated the noise, or rather the “sound”/resonance of noise that the factory fan was making vs noctua.
Factory was very loud, deep and profound while nouctuas fan generates less noise and the sound of that noise was simply acceptable (still is till today). It is at different pitch which makes almost unnoticeable at times.
Factory vs Noctua fan specification in cfm (cubic feet per minute) is the same and that is important.
Also, there is a big question how are you planning to use the system?
Off grid or as backup during power failures?
When MPII (any of then) is connected to the grid and uses that power, then it doesn’t generate much heat and the fan doesn’t turn on. Only when it is inverting from 48V to 230V will there be heat generation.
Personally, my MPII is in the study in the cupboard so it is closed up. I wouldn’t recommend keeping such device in e.g. living room… by a friend of mine, we installed MPII 3k and put it in the kitchen in one of the kitchen cupboards (that is the one from the screenshots). He uses the system for backup purposes so he has no noise.
Hey Bobby, your answer was superbly informative, thanks for the detailed explanation and the hint with the fan alternative.
I am planning to use the multi together with a grid connected to the AC input, but in a configuration maximizing the self consumption from a small PV array together with a small lifepo4 battery. Since this will be mostly a testing and learning setup, I am planning to get the 3k version. I am also planning to have MTS switches on each circuit (combined with circuit breakers), so I will be able to switch one or each of the circuits to the Multi supply and to the mains directly if needed.
So it will definitely supply power from grid together with the battery once it is available. The noise level is very important to me since it will be just next to living space.
Do you think there is a huge difference between 5k and 3k in terms of cooling, probably the fans are different?
I can imagine the 3k kicks the fan in under lower loads compared to the 5k. It will be super helpful if your friend can advise on when his multi starts to use the fan.
I have the MP II 3kVA and it should be similar to the 5kVA version. There is also no sound on low usage, but as you start using more (I would say ± > 1800W) the fans kick in and you hear them. It’s not that bad, but if you are sleaping next to them that propably would wake you if the fans start.
Mine is installed in the garage and no issue there.
I have the Multiplus II 3k and the fan starts running slowly when the load reaches about 700W during hot summer days (e.g. ambient temperature 28C). In winter the fan probably only starts up around 1kW load.
Fan noise is very subjective - it depends on both the environment (soft or hard furnishings), other noise sources, and one’s own hearing or sensitivity to noise. The fan noise, at lowest-speed, sounds to me as being similar to the fan noise from a microwave oven.
Thank you all for the precious “on-site” information.
How does this Multi II 3k cope with inductive loads? Can this one start things like vacuum cleaner, washing machine (up to 2kW) in inverter only mode (then grid is absent)?
I suppose, all of you have tested in similar conditions.
The Multiplus is an old-school low-frequency design, which means it has a big old transformer (Toroidal, so not quite as old-school) instead of the smaller HF designs you get with some others. This also means it is slightly better at handling loads with a high starting peak. However… you can count on roughly 200% Pnominal (ie twice the advertised power) for roughly one second, given that you have a strong enough DC source (ie the battery voltage doesn’t bottom out when you do that).
So… I’ve started a 1.5kW swimming pool pump with my 3kVA Multiplus. It let out one almighty groan and then succeeded in starting it). Washing machines is no problem.
I think a 2kw induction motor (which would have a peak on the other side of 7kW) will probably not start with a 3kVA. But a washing machine that draws max 2kW for the water heating… absolutely no problem.
to prove my forum nick… I did that once with a 12V 1200VA multiplus.
The cycle took longer than normal because the multi complained about overload during the heating cycle (although as far as I could tell the washing machine never lost power). Both the multiplus and washing machine still work…
Thanks for the information @plonkster and @all again.
Yes, the washing machine draws 2kW max (including water heating), the motor should be significantly less rated.
According to the specs, the 3k Multi should be able to peak 5.5kW (200% P nom.) for 0.5 sec and 150% P nom. for 5 seconds.
I found some info here.
In the overload video by Victron it was stated that a single phase motor can require up to 6 times the nominal current. Most probably I should look into this question current-wise. 5500W is around 24A, which in theory should be ok to start 4A motor (~1kW). If this is correct, starting 1kW+ vacuum cleaner machine can be a problem to happen or throw the inverter into overload state (do not know what happens in practice with it).
That is why your comments are superbly helpful, because you can throw some real life experience over those dark theory numbers.
My battery is planned with 16x100Ah lifepo4 cells (capable of 2C max) and 100A JBD BMS (probably can be upgraded in future).
Since this is my first attempt in those kind of systems and it will be more for testing and learning purpose, I decided not to throw too far with the 5k Multi, but still having the capability of running most of the appliances nearby (having grid connected as well as without it). That is why I am planning to take the 3k version.
My MP II 3KVA ran the whole house from a 100A JBD with 15x 80Ah cells, so this can be done. It should last you around 8h of loadshedding depending on your house and consumption. This setup gave me about a 60% power usage from PV and the rest from utilities.
If you have a large house then you would use much more.
Since then I have moved the stove/oven out from the Multi, the 80Ah cells was replaced with 120Ah and then later added back with another BMS (thus 15x 120Ah on 100A JBD plus 15x80Ah on 60A JKBMS). This gives me a much better consumption from PV.
I think the man is trying to figure out if a 3kVA will let him live his live more or less normally when there is an outage. We have a specific day of the week when the cleaning lady comes in. If there is load-shedding on that day, it is kinda sorta essential that the washing machine and vacuum cleaner can run. At least one of them.
And if you have a pool, and you have extended outages (like some people up North who were basically out for more than a week), it is also good if the pool pump can run. In my setup, the pool pump is definitely the LIMIT to what the 3kVA can do. If you are worried about that level of backup, get a 5kVA.
You all are correct, on this stage I am mainly planning and figuring out how such a system can be as versatile as possible. I am also limited by the PV array which will be around 1kWp, so I decided there is no need to extend the battery from the specified. above. The Multi is a different story, because it can be used even without PV, plus the option to move it to other place or even sell it and swap with another model. However, as a let’s say prototype system, I want to have all components in place, but also keeping the system compact and more in budget than the big one.
At the same time, it should be usable at all, providing power all appliances with grid connection and enough supply for essential loads during outage. It is also planned to max the self consumption with the ESS, so I can use the PV and battery power with priority and keep some Ah for outage (ups).
I must say that my overall power consumption is low and in almost all of the time it stays bellow 32A.
My first step will be to rebuild the power distribution board (unfortunately I will stay with TN-C el. installation, since I have no possibility to rebuild the whole cabling on this stage). I am planning to use MTS+MCB switches, so I can power each of the power circuits either from the mains or from the inverter. This will further give me the opportunity to decrease the load of the Multi if I need to run power hungry devices at the same time (since this is unlikely to happen).
I have shown the main idea (on the AC part for now) on the sketch. I am still not 100% sure whether bridging the Neutral on AC IN and OUT is ok, but I do not know how to do it in another way. I have included information from Victron Wiring unlimited handbook about the operation modes of the Multi.
I am also following the principle not to interrupt the Neutral at any point with a switch, etc.
Probably you can advise.
I must also apologize @Bobby for some how splitting his thread.
I assume this is what you get from the supplier? As far as I know, the standard way to deal with this is to bond TN at the point of supply, and from there on you never mix earth and neutral again. In other words, though you get TN-C from supply, you treat it as TN-C-S beyond that. In other words, you will not connect the neutrals of the inverter input and output together.
I am not a qualified electrician however, but again, as far as I know in South Africa, that’s what you’d do.