MPPT reduces power when battery full

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jens-zeidler asked Feb 4, '24

MPPT reduces power when battery full

Dear Victron Community,

I have noticed a problem with my Victron setup. As soon as the battery is 100% charged, the Smart Solar Charger reduces its output.

The Victron setup is an addition to an existing SMA system. The modules of the SMA inverter as well as the modules connected to the MPPT are mounted identically in terms of orientation and inclination. Accordingly, they should also have a similar power curve over the course of the day.

As you can see from the following evaluation, this is no longer the case as soon as the battery is full. Roughly speaking, 50% of the yield is lost due to the behavior:

A rough sketch of my system to help you understand:

My configuration in VE.Configure:

And the settings in VenusOS:

Any idea why the Victron system is wasting solar energy instead of sending it to the grid?

Multiplus-II MPPT Controllers battery

soc-mmpt.jpg (206.6 KiB)

victron.jpg (149.3 KiB)

veconfigure.jpg (462.8 KiB)

venus.jpg (729.7 KiB)

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Answer 1 · 2024-02-04T17:50:41Z

ahtrimble answered · Feb 04 at 05:50 PM

Sorry, I can't understand the labeling on the screen shots.

I can tell you that each charge mode has a different voltage. Once the batteries are full (100% usually) on bulk mode they go into absorption mode which is usually a lower voltage than bulk. And then your MPPT will shift into float mode based on the MPPT settings.

Your battery vendor will give you the voltages and other points for each mode.

The draw on the battery brings down their voltages which triggers the MPPT to switch modes to a higher voltage charge. I wouldn't want to keep my batteries going on bulk mode once they reach 100%...not good for them.

Check with your battery vendor to make sure you have the right settings for your specific batteries. Other than that I can't help much.

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Answer 2 · 2024-02-04T18:08:04Z

nickdb answered · Feb 04 at 06:08 PM

Perhaps rather post in the German section.

You’re limiting max charge voltage in dvcc, that isn’t intended for permanent use.

What happens if you remove that restriction?

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Answer 3 · 2024-02-04T19:00:56Z

Alex Pescaru answered · Feb 04 at 07:00 PM

What is that square modification in SOC between 10:05 and 10:25 ??

Is just like something else is telling the system which is the battery SOC....

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Answer 4 · 2024-04-21T19:46:45Z

James B answered · Apr 21 at 07:46 PM

I had a similar problem which I fixed today. I use mode 3 control, and I was incorrectly setting the ‘Max PV Feed In’ - it was being set too low and oscillating bettween low/high because I had no smoothing/filtering on it in my control loop.

For modes1/2 control, which I guess is what you’re using, this parameter is controlled in the remote console under the ‘Grid Feed In’ section - it’s called ‘Maximum Feed In’. Try disabling the whole thing (turn off ‘Limit system feed in’) if it is turned on now, or just raising the max.

Make sure both ‘feed in excess’ switches are ON.

Hope this helps.

img-3389.png (24.1 KiB)

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