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gs_nz avatar image

MultiPlus sparking inside when grid connected - service centre found nothing wrong with it!

My 2.5 year old MultiPlus has slowly developed a fault where over the last 2 months, when it started disconnecting the grid for no apparent reason. No warnings or messages on VenusGX console or VRM. The unit is installed in a motorhome, it's been working fine for more than 2 years and every few days I'm connected to a new 16A AC230V supply (via a "UK" caravan socket) at various campgrounds. This behaviour seems to happen irrelevant of location (and thus the quality of the grid supply is not the problem). The fault is when I start using some AC230V loads in pass-thru mode (without using the inverter), I could hear sparking inside the multiplus, coming from the bottom right corner, and eventually something in the multiplus trips (distinct click can be heard) and MultiPlus starts inverting to supply the load, which then works fine. After sometime something clicks again, and it the cycle starts again...

Here is an example (1 minute), with grid connected, powerassist OFF, current limit set to 0A (so that charger is taken out of the picture, and pass-thru is forced). I connect a 1000W fan heater - hear the sounds coming from the bottom-right corner of the MultiPlus:

https://www.youtube.com/watch?v=iIPu9M-f6K8

Somebody please tell me whether this is normal or not, and what could possibly be the problem? I would like to tell the service centre where to start looking...


The service centre says they found no problem with it... It's not like I would go into all the hassle pulling the unit out, sending it via courier, waiting for it for 1.5 months, while stuck at a single location, as I have no way to charge my batteries other than solar right now - just to hear "there's nothing wrong with the unit". Anyone had a similar experience with Victron's authorised service centre taking over a month to "look" at the issue and then telling you that there is no fault? What can I do to escalate it?

MultiPlus Quattro Inverter Chargerfault
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My wife mentions that she couldn't hear the sparking on the youtube, until she turned up the volume at 19 seconds on the video ( https://www.youtube.com/watch?v=iIPu9M-f6K8 ) - so turn up the volume to the max at 19 seconds. I promise, there is no scary face in this video ;-)))

2 Answers
Daniël Boekel (Victron Energy Staff) avatar image

Hi @gs_nz

Sounds indeed like a problem at AC-input, yes could be the relay, but please also check the input plug, if that is not seated well it can go bad also.


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That's a tough one now, as the MultiPlus in question is no longer connected... Before sending the unit back to the service centre, I checked the connections as part of the troubleshooting and it appeared to be sitting in fine. The service centre didn't find any problems with it, and in mean time the new MultiPlus didn't have any of these issues. Once I get the old unit back (after paying the ransom/inspection fee) I will be able to do more testing.

Hi @gs_nz

Ok please keep us updated, and when there are issues we might be able to help.

ejrossouw avatar image

@gs_nz Not much information to go on so maybe if you share the model, voltages / current etc. at the time it will be great. There are many variables and also how is the system grounded etc. The incoming lines from the shore may have a problem and that is why the relay disconnects the system when it cannot sync. etc. I'd definitely start with a proper check of the wiring, fuses etc. which may ultimately result in the relay doing its job as intended..

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Multiplus Compact 12/1600/70-16 (12V, 1600W inverter, 70A DC charger, 16A AC input/output/transfer switch)

Voltage DC: 13.5V - almost fully charged Lithium 500Ah 6kWh battery
Voltage AC: 235V 50Hz, drops to AC230V under 2000W load, powerassist OFF

Current limit: 0A (to make sure the charger doesn't kick in to help isolate the issue)

So take DC12V system out of the question, as everything works fine when inverting.

Sparking when on AC230V - it happened in every campsite we stayed at for at least a month, getting progressively worse. When I say worse, it used to "click off" the grid at 2000W - kettle, later in the we couldn't run anything over 300W, and finally 100W. As long as the current was under 1600W, the inverter happily carried the load.

I could also replicate this by putting no load on the output, but increasing the Current Limit to invoke the internal charger, with the same results. So initially I could have the Current Limit set to 16A, and the MultiPlus charger would start charging the batteries at the full power - around 810W - 3.6A on AC (around 60A into DC), dropping down over the next hour to 600W 2.6A on AC (45A into DC) when the MultiPlus got warmer (I was told this is normal, even when MultiPlus is well vented - and it is). We noticed that it was "clicking-off" the grid, we initially thought - bad power supply, but this was happening at different campgrounds rural and urban - so the "bad power supply" theory was no longer feasible. We reduced the charging (Current Limit) to 2A and that initially fixed the issue (no more clicking), but progressively we got to 0.5A (around 60W going into the battery), and finally, even that "clicked-off". At that time, no matter what current went in, the sparking you hear in the video was happening every-time we connected to the grid. I checked the AC and DC connections underneath, on the battery, all fuses - everything was in order. I even borrowed an IR camera to see if there was something overheating where it shouldn't be. Negative.

So we stopped connecting to grid and contacted the supplier, and sent it to them. I kept all the cables in place (AC IN, AC OUT, GND, DC IN, Ve.Bus), and sent the unit bare back to them. Thanks to COVID-19 it took 2 weeks to arrive and then 4 weeks to hear back that they couldn't replicate the issue!

After a week after sending the faulty unit in, I bought another MultiPlus 12/1600/70-16 (identical) to be eventually fitted in our off-grid home, but for now, I thought it would be a good slip-in replacement until the faulty unit is repaired. That unit arrived just over a week ago and has been working without any problems. No other wiring was changed.

I'm puzzled as to why the service centre can't replicate the issue. The only thing that I could think of is that the relays for the transfer switch might be faulty - maybe they welded slightly, maybe they just had reached EOL, but I don't know. I'm not sure where to next, either.

Ground:

The chassis of the MultiPlus is connected to chassis of the vehicle.
AC 230V ground from outside comes in on the AC-IN plug directly from the outside plug to the MultiPlus. Then MultiPlus has a Ground Relay and it's enabled, which is activated depending on the status (inverting/AC pass-thru). We have RCD on the line-in, and then another one after the MultiPlus AC-OUT (required by NZ and AUS electrical standards). We never ever had any of the RCDs trip.

See the paragraph from manual:

Ground relay (see appendix B)

With this relay (H), the neutral conductor of the AC output is grounded to the chassis when the back feed safety relay is open. This ensures the correct operation of earth leakage circuit breakers in the output.
If a non-grounded output is required during inverter operation, this function must be turned off. (See also Section 4.5)

Thank you for taking the time to get back. Ok, so you concluded the inverter has a gremlin, likely a literal one inside, by replacing it. I probably can only suggest you open up the unit and get a good blast of air through it and clean it out. Critters have been known to get inside and cause havoc. Maybe ask the service centre to do it for you now that you have a spare? If it is indeed a bad connection that expands under load and causes arching, they should be able to spot it eventually one would hope. Also, if you have access to ve.config you can disable the charger from there.