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steve avatar image
steve asked

Multigrid II issues

Hi,


I have 2x Multigrid II's in parallel with a Fronius 5kW AUS on the load side with the entire house. I have a BYD 10kWH battery in the IP56 cabinet

When first programmed and commissioned it seemed to work fine until the PV turned off, then the battery seemed to export to the grid.

The next morning, once the PV started back up, the battery re charged, but whatever the PV was putting into the battery, it was also importing the same amount from the grid into the battery. This went on for weeks with support from The Netherlands and Ciaram from My Energy SA trying to solve the issue. Eventually with Ciaram's help, we updated the firmware which had come out that day and we didn't have any issues.

Three weeks later after everything had been running smoothly, the Master Multi went out on overload and shut down power to the house. We have now bypassed the entire system and he is now back on grid only.

Nobody was home at the time this happened, the customer didn't know until he got home for lunch that day. According to VRM it happened about 0755 in the morning.

I have not yet been back to site since, and it won't let Ciaram remotely reset the Multi for some reason.

Has anyone else had a similar issue? What should I look for once I'm back on site?

Ciaram and Wayne from My Energy SA have been very helpful, but just thought I would ask on here as well.


Thanks



battery chargingmulitgrid 2
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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ commented ·

I will do some research on this and update this comment with what I discover.

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3 Answers
steve avatar image
steve answered ·

Ok I finally got around to replacing the master Multi as it would not reset.

Everything was running perfectly for 3 days and I thought I had it sorted, but both the slave and the master went into overload last night at exactly 1730. I went around and reset them both and started up running perfectly again... 12 hours later and it's still running beautifully.

I have checked over VRM in the history and everything seems fine. There were no big loads, the customer was just sitting in his lounge watching TV when it went off, there were no high voltage spikes from the grid.

The only thing that looks suss is the battery voltage around that time. About 10-15mins before it went into overload, the battery voltage spiked up too 64V. Also, once it reached 100%soc the battery voltage kept rising, which is when it peaked at 64V a few hours later. The time of the overload though, it was 59V with no current.


I have the ESS assistant installed on both Multis and the absorption (55.2V) and float (55V) are set as per the "Victron and B-Box" instructions.

Really not sure if I have a faulty slave mulit now or whether its my installation and commissioning. I'm all out of ideas for the time being.

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stefan avatar image
stefan answered ·

it looks on the photo that both units are installed in serie and not in parallel.

See: https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems

DC cabling wrong.pdf

Please control if the units are interconnected as on drawing.


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steve avatar image steve commented ·

Thanks Stefan,


Yes that is how they are wired. They are in parallel but are not the same length. Positive and negative are the same length though.

I will change to same length and see how we go.


Thanks

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stefan avatar image
stefan answered ·

If it is wired like in my hand drawing, your connection is not in parallel it is in string. See attached scheme to see the difference. Do not forget to install for each MultiPlus II one fuse with 125A (is not mentioned in my scheme).parallel connetion rigth and wrong.pdf


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porcini avatar image porcini commented ·

Both is a parallel installation, but what you mentioned is correct anyway. I am wondering if this will solve the problem.

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