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Multiplus ii- Onan 4000 generator being rejected, maybe

This is an installation on our RV. Multiplus II 2 x 120 with BattleBorn batteries. Inverter runs fine. When plugged into shore power, it switches to mains just fine. When plugged into the onboard generator, power is rejected, presumably, as there is no indication of incoming power when in inverter mode. There is a clicking every 20 seconds or so, which I am guessing is the ground relay opening when trying to synch. If I switch to charging mode, the mains LED will flash. I just got the VE bus bluetooth module, in the hopes it would have some error codes, but I can't find this. The Victron Connect app shows AC in around 120V (like 122V) and frequency around 59-63 Hz. When starting the generator, it shows synchronizing (or something like that) up until the first clicking, and then just shows the AC in as above, with zero current. Switching between shore power and generator power is accomplished by plugging the shore power plug into the generator outlet. I thought I saw a caution to not use the vehicle 12v ground as the AC ground, and the generator was initially set up this way. I have tried disconnecting the generator ground entirely, and connecting ground and neutral together at the generator, but not connected to the chassis, all without success. I am guessing there is some neutral-ground issue that the Multiplus doesn't like, but I am hoping someone knows of some setting that I need to check.

Multiplus-IImultiplus ve.bus
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derrick thomas answered ·

Is dynamic current limiter checked? Have you tried enabling/disabling weak ac input? If you have a MK3 you can connect to a PC and open ve.configure and you can see why the ac input is being rejected.

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emergencycheck answered ·

The Victron connect page implies I can configure from the app, but I am not seeing it. I will work on the VRM stuff it that is what is needed.

I found that in the course of my troubleshooting/shotgunning, I connected the generator AC ground to AC out ground. Disconnecting this allowed the generator to pass through, once. After that, it is getting rejected.

There is 2 MegaOhm continuity between the generator neutral output and chassis ground, which I am guessing would be enough to cause ground fault problems.

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derrick thomas avatar image derrick thomas commented ·
The neutral and earth on the generator should be bonded. To make settings changes in the multi with victron connect you need to be connected via a MK3 adapter either to a PC or a mobile device using an OTG cable. Like previously stated, if you connect to a PC with the MK3 and open ve.configure you can see in real time why the ac input is being rejected. Otherwise it's all guesswork.
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emergencycheck avatar image emergencycheck derrick thomas commented ·
I was hoping that the VE bus dongle would give me that access, but apparently not. I will order up a MK3 adapter and hopefully it tells me what's up.
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emergencycheck answered ·

I also found that when inverting, AC out ground is connected to chassis ground.

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derrick thomas avatar image derrick thomas commented ·
That is because the ground in the main breaker panel is connected to chassis ground, as it should be.
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emergencycheck avatar image emergencycheck derrick thomas commented ·
I checked the onboard breaker panel, and that is correct. Neutral and ground are not connected there, which I also believe is as it should be. However, there is around 5 MegaOhm continuity between neutral and ground, which might be internal to the Multiplus II, since there is no other connection that I know about. When inverting or on shore power, this goes to zero, which is also how I believe it should work. I have gone and connected generator neutral, generator ground, and chassis ground at a single point, and generator power is still rejected. I am suspicious that the Multiplus II doesn't like incoming AC ground to be the same as chassis ground.
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derrick thomas avatar image derrick thomas emergencycheck commented ·
"I am suspicious that the Multiplus II doesn't like incoming AC ground to be the same as chassis ground."


This is standard in North American rv's. That is not your issue.

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emergencycheck answered ·

OK, I've got the MK3 and I am not seeing where I can see why incoming AC is rejected.

ve-config.jpg

I've toggled weak AC and dynamic current limiter, no success


ve-config.jpg (159.5 KiB)
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Related Resources

MultiPlus-II Product page 

MultiPlus-II Manual

MultiPlus-II 230V Datasheet 

VE.Bus Error codes

Additional resources still need to be added for this topic