MPPT supplies too high output voltage to battery (17,55V and higher, while limited to 14,2V)

DIY
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Dear all,

I’ve read quite a few topics and manuals. Therefore, before my first post introduction, I would like to thank you for your contributions and replies on this and other topics, to share knowledge.

So now it is time for my first inquiry, to enrich this forum, and to help out me and others in the future.

The issue is:

  • An MPPT 100/20 has been set with a max output voltage of 14,2V
  • The output voltage started creaping up to 17,55V and eventually even to much higher voltages.
  • The MPPT stated charging was off, but yet the higher voltage was on the output poles
  • A too high voltage eventually destroyed the Victron Phoenix 12V1200 and a few domestic appliances, like a refridgerator

The situation is as follows, for an offgrid house:

  • System layout is minimal and simple: an MPPT 100/20, connected to a Phoenix 12V/1200VA and a 12V lead acid battery. The MPPT is connected to two regular PV panels with roughly 850WP and 80VoC when placed in series. The MPPT is on the latest available software version.

I have screenshots, but don’t see how to attach it to this post.

The reseller says; we’ll send a new one. But I am concerned the new one will do exactly the same, unless I fully understand why this happened in the first place.

Please advice?

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To add an image, just drag it into the editor where you write your topic.

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Thanks Nick,

Please feel free to suggest how this may have happened. See attached images.

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IMG_0550
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Did you build a bluetooth network of all your components? Do you have different chargers for different batteries?

I had something similar in the past where one device gave over bluetooth network the voltage to another device which should not have been connected to each other. The other charger was increasing the voltage continuously but the voltage measurement of the other device was not increased as they were independed/seprate charging networks. So the components where mixed up, cross giving information which increased the charging voltage incorrectly. Disconnecting the bluetooth devices/network solved the problem.

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Hi Rick,

Thanks for the suggestion and I wish this was the case, but unfortunately there is only one MPPT and no VE or Bluetooth network.

Until now it remains a mystery why this happened. Replacing the MPPT may not resolve the issue and that is my main concern.