question

Robert Bazalgette avatar image
Robert Bazalgette asked

The PV inverter assistant not working well

Daniel Boekel@victronstaff

5 Kw Multi plus inverter, Blue solar 250 / 100 charge control. My PV AC Thor. 5.2 Kw PV. 48v LiFePo battery pack 216 Ah.

The PV support assistant is not working well. In the morning the solar input charges the batteries up to absorbtion level. The Multi then increases the frequency, and the MY PV AC Thor sends power to the immersion element.

As soon as the batteries reach float level, the Multi reduces the frequency to 50 Hz, and the AC Thor stops delivering power to the immersion. For the rest of the day the frequency remains at 50 Hz even when there is plenty of surplus PV power.

Please advise how to improve this. The AC Thor is an expensive device, and it is frustrating that we cannot get help sorting out why it is not performing as it should in conjunction with the Multi plus.

Hot Water Diversion
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2 Answers
JohnC avatar image
JohnC answered ·

Hi @Robert Bazalgette

I'm sure you're well aware that Assistant was never designed to control a dc coupled mppt. It's trying to control to it's own charge settings, which can't be synchronized to the mppt's. So when the mppt drops to float and backs off the V, the Multi can't reach it's own target and the Hz drops.

It's really an unsupported application, and getting frustrated with Victron support is unwarranted. I'm actually surprised it works at all, given the Multi isn't actually charging in it's own right.

Maybe you could try having a fixed Abs time in both the mppt and Multi, but I can see potential issues there too.

Or a flat charge V in both if your Li batts can live with that.

If you have a GX device, use DVCC so you know both are using the exact-same V.

But I'm just guessing..


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shaneyake avatar image shaneyake commented ·

Yeah, also very surprised it is working at all. Typically with DC MPPT frequency will stay at 50hz always. This is a very not supported config. If you had some AC-PV it would work tho.


The AC-Thor can be controlled via Modbus TCP. You will need a Cerbo GX to do this but you can have the Victron system directly control the AC THOR. With some custom setup.

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Robert Bazalgette avatar image
Robert Bazalgette answered ·

Thanks very much for that. The Multi in this setup has a GX, it is a multiplus II GX. There is a VE direct cable between the charge controller and the Multi. I was following Victron's recommendation for diverting excess solar to hot water, and their literature suggests the MY PV ACThor. I have been struggling with it for months and yours is the first response that explains why there is a problem. All I have to do now is find a solution. I will look into DVCC as I don't know what that is. Thanks again for taking the trouble to answer.

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shaneyake avatar image shaneyake commented ·

Sorry, I was mistaken.
You are doing it correctly via this guide, I am only used to the ongrid setup which uses coms.

https://www.victronenergy.com/live/actor_offgrid

Here is another thread with some good info. Looks like you just need to adjust the absorption voltage to be lower it will keep the frequency above 50hz. You need to have MPPT absorption voltage higher than multi absorption voltage.

https://community.victronenergy.com/questions/51199/ac-thor-9s-15000-quattro-not-frequency-shifting.html

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