question

Have you tried switching ups mode on/off? Weak ac input on/off?

If you have a MK3 you can connect to a PC and check the log from veconfigure to see why ac input is being rejected.

Hi Derrick

Thanks for the reply - I do have the Mk3 and access using veconfigure and I have turned weak ac on (also tried in the off mode) - no difference.

I have not tried the UPS on/off option, I will take a look at that and see if it makes a difference

Here is what I find confusing - if I connect a really cheap, low power, Chinese generator to the system, it all works, except it really overloads the poor generator. The MP2 AC mains in LED lights up, it syncs, and then it tries to draw power, but its all too much for the el cheapo Chinese generator. I then unplug the power lead from El Cheapo and plug in to the specially set up for PV systems diesel 8.5kW generator and nothing happens, no Mains in LED, zilch. I check the AC input, its 230v, I check the frequency with my Fluke, its fine, I add a 2kW heater load to the generator, heater warms up, generator does not even notice, not miss a beat. So why on earth does the Victron not like this generator?

I am sure this must be something very silly, but so far, I dont see the funny side, but maybe soon I will be laughing :-)

I did this, there is nothing in the log. But I will check again

The only check I have not made is to look at Hyundai output on a scope. Perhaps there are spikes or a DC offset that is confusing the MP2? Anyone any experience of these things?

@RisPhil

Take a look through this.. https://www.victronenergy.com/live/multiplus_faq

Gensets can't buffer like grid can, and you'll almost certainly need to tick Dynamic Current Limiter to bring on the load/charge over a few seconds rather than in one hit. It may even be the genset rejecting the Victron..

Try reducing the AC Input Current Limit on both Multis for testing. You can optimize this later when you get it working.

And then there's other undocumented things, like maybe a dicky power lead, that can cause things like this. I've suffered that myself.

Just be patient and watch for clues. All gensets are different, and you need to suss it out. You'll find the issue, hopefully sooner than later..

Thank @JohnC. I have set Dynamic Current Limiter and also adjusted the AC current limit but be aware that the MP+2 does not even recognise that ACin is present because the charger side Mains On LED does not light up when this generator is connected even though I measure 230vac at 50Hz coming in to the AC in terminals. If I unplug this large diesel brand new generator and plug in a small cheap Chinese petrol generator, immediately the charger mains in LED lights up and after a few seconds it tries to sync, it even succeeds to sync and overloads the little generator. So I cannot see how this is anything to do with Victron settings?

If the problem was failing to sync, or it clicks in and drops out, yes I get it, but the AC from the Hyundai is not recognised whereas the AC from the cheap Chinese generator is recognised, no other changes made to the system other than unplug one generator and plug in the other. A normal test meter shows no difference between the AC outputs of the two generators, both at 230vac and 50Hz. Obviously there is a difference, hence my idea to look with a scope

I am wondering what conditions Victron set for the AC input in order for the AC in LED to be illuminated?

Obviously within the input AC voltage range and frequency tolerance, but presumably other conditions need to be met?

What is your earth rod impedance and is the rod connected to the generator chassis with a 10mm cable (and to the MPs). I think Hyundai normally link earth and neutral but check that this link exists (measure at the generator output socket with it not running)

I was recently called out to a job with a fully dealer commissioned Hyundai 6.5kVA generator only to find the output was at 52.5Hz. By loading it at 3kW the speed dropped enough to get it down to 51Hz. I also noticed a lot of harmonics at no load. Try a slightly larger load?

The Multi requires a stable frequency on its input in order to sync to it. Once that happens, the AC input relay will close and you'll hear that thunk. I believe the AC input LED lights at that same time (which is what Derrick said above). If the generator RPM is not stable then the output frequency will also vary. I don't know how stable it needs to be in order to be recognized. (Of course, inverter generators produce a stable frequency regardless of engine RPM.)

One thing most people suggest for generator is to select wide frequency range. When off, the frequency must be within 5% of the set frequency. When on, the Multi will accept a wider frequency range. But I don't know if that relaxes the stability requirements.

Hi Kevin

Thanks for the thoughts and helpful comments. I will be going through the entire system again on Tuesday with digital frequency meter, voltmeter and oscilloscope, so hopefully I will be able to find the source of the problem. Will post my findings (or perhaps ongoing problems) on here.

Phil

Yesterday I made two videos resulting from a quick lash up test comparing the brand new Hyundai diesel, sold as being especially suitable for integration into PV systems and an old cheap small petrol generator. The cause of the problem is now obvious

PS, I made a mistake earlier in one of my responses - the MP2 mains input LED only lights up when the the input is accepted by the system - not as I had written, when any AC is present. My mistake

I have informed the supplier and also Hyundai tech support (whose response so far has been to inform me that they have sold thousands and never had a problem, implying its all my fault) and will post their responses on here for anyones future benefit

Hyundai have offered to supply replacement AVR units for me to fit. I suspect the generator may work better without AVR, but I will try, once I have it in writing that the warranty will not be voided

Finally, I have installed the new AVR and it solved the problem, the output from generator is now a proper sine wave, the MP2 syncs and it charges the batteries. Hyundai supplied faulty generator from the outset. For those who live in Spain or Portugal, Hyundai outsource their tech support to a company called GRV Power. These people did nothing to resolve the issue, their response was simply that they have sold thousands of these generators and never had problems. They also offered to look at it, but made it clear that they would only check voltage and power output, both of which were fine. It was THD that was the problem.

New issue, if anyone has any ideas, syncs fine, charges batteries up to around 2kW from the generator, but if I set power limits to above this amount, MP2 disconnects from the generator. I can see no issue with the sine wave, voltage or frequency, this being a 5.5 kW generator. Any ideas for me to explore would be gratefully received

Is that a 16 amp plug in the photo, or a 32 amp plug? A 16 amp plug limits the output of the generator to 16 amps X 230 volts, or 3.6 ish kW. My generator calls itself a 5.5 kva, but I only have 16 amp plugs. If I had two loads I could get the full 5 kW (ish) out of my generator, but never out of one plug.

And not sure if you have 2 multipluses in parallel like I do? In case you aren't aware, the current limit needs to be divided over the two. So my veconfigure files have current limit is 7.5 amps in one and 7.5 in the other. Because I don't have a 32 amp plug on my Generator, I have a 16 amp plug.

DHY8500LEY 7.500 KVA

Frequency: 50HzContinuous power: 6.000W

Max power: 6.500WVoltage: 230VCurrent: 27AOutputs: 1x16A / 1x32A

Diesel tank: 14ltrMax continuous operating time: 4.5 hours at 100% loadOperating time at 50% load: approx. 10 hoursNoise level @7m : 77 dBa

Battery charger: 12V 8.3A

I had something similar with a Hyundai DHY8000SELR-T.

I'm not sure if this is relevant as it has single phase 230V and 3 phase 400V, but worth a try.

On checking the single phase 230V AC output I found that the voltage on the two legs was a long way out of balance(AC multimeter to earth on the generator). Connecting neutral to PE in the CEE 32A plug of the cable sorted it. PE in the cable is, of course, connected to the Multiplus. (Actually an EasySolar). Seems the Victron kit is sophisticated enough to recognise this.

If you have concerns, don't try this out. I struggled with this for a while before doing it, despite a qualified boat electrician saying try it... The multi has an internal connection via relay between earth and neutral. But this only happens on battery/no AC in. So it sees the generator as grid/shore power and does not bridge with it's relay. Net result no earth loops.