MP2 kills generator AVRs

Q&A and troubleshooting
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1

I have a Multiplus-2 5000/48 here, V552, running with a Cerbo v3.52.

I’ve been struggling with charging from the generator on this all winter, with the generator cutting out regularly and significant voltage drops (below 170V on a 230V system) on the generator, indicating issues with the AVR.

(Dynamic current limiter, wide input range all used, UPS is off)

For a long time, I thought it was either a bad AVR or an issue with the Hyundai 6KVA diesel gen I was using. Eventually the AVR burned through and I replaced it. However I also stopped charging via AC-In and instead introduced an EG4 Chargeverter, to completely bypass the MP2 charger.

I’m done with fiddling with the MP2 settings to get this to work properly and I am now convinced that the MP2 killed the AVR. Why? Cause on the EG4 it runs super smooth. Gentle ramp up of the current to the set limits, then it just ticks away. As I charge into DC directly, no more flickering lights and the risk of getting my electronics damaged.

Today, I got curious and switched the setup back to the AC-In. What happens? Voltage drops to ca. 190V immediately and a minute later, the AVR is burned through again. Thankfully I now keep a spare all the time and swapped it out. Back on the EG4, everything runs smooth again.

I have followed all the information available over the year, like this one:
MultiPlus Generator FAQ [Victron Energy]

Yes, the 6KVA gen is a bit on the smaller side, for a 5KW system, but I am never running this without current limits and usually no more than 60% load. Most importantly, it just works perfectly on the EG4, so please no pontificating about the statements in the FAQ etc.

There seems to be a significant difference how the MP2 handles the loading of the AVR, compared to the EG4. I am a Victron fan. I am providing this feedback, so that Victron can hopefully improve this. I have no interest in dealing with a US manufacturer and importing stuff from there, but I cannot argue with the results, which are frankly very impressive.

I hope this can be addressed in software, or even if Victron create a similar product. Personally I prefer to have this charger tie into DVCC as well and have proper VRM statistics. But its the middle of winter and having charged batteries (off-grid) is kinda more important right now.

2

The Multi is an ‘inverter’ with a toroidal transformer and is therefore extremely robust and powerful in the areas for which it is to be used. Injecting the charge leads to an enormous increase in the primary current of the primary winding. The AVR generator reacts to this by readjusting. This swing-up leads to the disconnection of the multi from the generator. The typical build-up during loading and unloading.
The other charger you are using is a typical HF charger
which is completely different … and works better. It reacts completely differently to voltage and frequency dips.
I don’t use the Multi for charging myself, but use extra Eltek chargers so that my AVR generator doesn’t cause the same thing.

3

I wish Victron had something suitable as well, but the Skylla is no comparison to be honest.

4

The RS series may already be an alternative here and a glimpse into the future of Victron.

5

Don’t say that… The low frequency inverters lovers will have a depression… :smile:

6

I love my two slightly buzzing toroidal cores … :sleeping:
Maybe because they don’t need charging … :wink:

1 Like
7

A different issue with another brand of inverter / chargers also drove me to install a Chargeverter GC. I’m glad I did.
I use a Honda EU7000 so have 5kVA of super-stable AC at my disposal. Its actually far cleaner than the Chargeverter needs.
The CV GC charges my 48V @ 450Ah LFP battery without fuss.
The charging engine is a pair of bog-standard 50A Telco chargers of the type found in countless thousands of switching stations world wide. Robust and simple.
The programming and controls are definitely Chineseum, but once set, it works every time. I run mine manually, but it would be trivial to enable 2 wire start to the generator.
I like the charger’s built-in taper of charge current when the battery approaches 98%, and the stable output during constant voltage (Absorb) so that top balancing proceeds smoothly and with good visibility.
While giving up a little system efficiency by “charging / discharging” the battery simultaneously, overall, the CV GC measures in at 90% conversion efficiency, much better than my inverter’s 80%, so there’s actually a net gain on system efficiency.
The inverters stay inverting, the charger charges, the generator purrs along (CV GC set to 4kVA draw, so very cool, quiet operation.)
I’m happy with that.

8

AVRs usually die because of overload or having to work to hard to stabilise the sine wave.

So maybe just need to use an even lower input current limit? Basically would have been what you did when you switched chargers. The charge onky charges doesn’t support loads as well so half the job is no longer being carried by the generator.

Qlot of set ups don’t take into account derating due to height above sea level. (So a 6kVa can actually be a 3.5kVa running at max load which is maybe 15A)

I have fiddled the chinesiest 2kVa to be accepted by a 5kVa before. It can be done. Had to tune both the generator and the inverter.