No amps, high Voltage as soon as over 15ish Amps

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Philipp Czakert asked Oct 17, '21

No amps, high Voltage as soon as over 15ish Amps

Hello Victron Community,

I have a problem with my setup, and I am very confused how it happened. We live in a trailer and have been using the MPPT 100|50 charge controller, the BMV-712 Smart with 4 batteries (24v/250amp in total, those AGM batteries), 4 12v solar panels (wired to be 24v), a 3500W pure sine inverter (which still works) and we have not run into problems for almost 2 years!

All of a sudden we are reading 38V and 0A!

But not all the time. In the morning it does charge the battery, but then it shuts down as soon as it reaches maybe 15-20amps (25 is our max, so I believe it is more to the lower end).

If there is no hidden fuse in one of the building parts (is there?) I can rule out a fuse being the issue.

We did have a very rushed wire connection that was hit with wet snow the other day, but I since rewired the whole thing, and the issue persists.

We are totally off grid and need help! Thank you so, so much!

Attached are a few pictures that hopefully help.

I am certainly not an expert (as evident) so if you need more information, please ask.

mppt charging

screenshot-20211017-113339.png (95.2 KiB)

screenshot-20211017-113353.png (124.3 KiB)

screenshot-20211017-113407.png (114.9 KiB)

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Modifications Space

Node Red Space

Answer 1 · 2021-10-17T18:26:52Z

Mike Dorsett answered · Oct 17, 2021 at 06:26 PM

Two things to do here: 1) Check the settings for the mppt - does the max battery charge current drop to zero? Also, check for any high resistance in the battery to MPPT connections - less likely. Finally, try resetting the MPPT to defaults using the connect app, and see if this restarts it. There is a fuse inside the MPPT, but if this was blown, it would not work at all. Also check that the firmware is up to date as there has been a recent change...

I would also wire all the panels in series (assuming voc of about 22V?) rather than 2 series 2 parallel. The MPPT will function better this way.

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Answer 2 · 2021-10-17T18:44:19Z

Philipp Czakert answered · Oct 17, 2021 at 06:44 PM

Yes, the current is at zero (and Voltage at 37). Firmware is up to date and high battery resistance does not seem to be the problem.

Can I wire the panels in series while having a 24v battery bank? I am limited that way because of my inverter (24v)

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Answer 3 · 2021-10-17T20:05:35Z

michelg answered · Oct 17, 2021 at 08:05 PM

Hi Phlipp, can you try to connect only a group of PV panels at a time ? If for any reason one is damaged, it can ruin the setup. The idea is to be sure that each panel works fine and provides the expected VDC and Amps. Checking every element in your installation is very important, I am also off-grid, and have seen unexpected things with connectors (rusted breakers because of rain infiltration)...

Michel

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Answer 4 · 2021-10-17T23:52:30Z

Philipp Czakert answered · Oct 17, 2021 at 11:52 PM

Thanks for your reply michelg

I have checked every element, besides the charge controller itself, and even went and got some new batteries. The problem persists. I am now very sure that it is the MPPT 100|50 charge controller causing the issue. It almost seems as if there was a short circuit and the charge controller jumped into "protection mode" and now does not get out of it. After all it started with the wet snow... of course it could be somewhat of a coincidence...?

If there was a short circuit do I have to "tell" the charge controller to snap out of it already? I still can't explain why it worked in the morning until about 11am...

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