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logic28 asked

MPPT 250/100 output shorted

After 6 months of smooth running, during this evening my solar system suddenly shut down so I went to the solar shed assuming a fuse had blown a so it was.

That was a 125A fuse in the Power In on a 100A battery, I immediately suspected a fault in the system so I changed the fuse and isolated all components reconnecting them one by one.

The battery was fully charged today by solar and only used down to 90%.

Every time I connect the Battery side of the MPPT and restart the system, the battery goes into protection mode and shuts the system down displaying a "Short Fault" even with the PV isolated and the input cables disconnected.

I have two 250/100 MPPTs however the second one was not connected to PV as yet but just to the system and visible on Cerbo, both of them are having the same effect

With the MPPTs isolated everything seems to work just fine and the inverter produces energy and delivers it to the building.

I tested the resistance of both the Battery side and PV side of both MPPTs and they are respectively 195.7kΩ an 950kΩ for the first one and the other 250/100 it seems to read similar values.

I cannot believe that both 6 months old chargers burned at the same time with no solar current at the time.screenshot-2024-02-02-at-205652.png

My peek PV voltage today never exceeded 221v as per image attached and as far as I know it never went near the limit of 250 before, in any case, as I said, the problem is the same with the second MPPT and that has never seen any PV input as yet as I was going to install 5 more panels next week.

Could the problem be in the distributor perhaps?

Any similar problem in our fraternity?

Thanks

img-20230918-100517-775.jpg

MPPT Controllers
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ejrossouw answered ·
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logic28 avatar image logic28 commented ·

I've just come back from the shed and discovered that it seems to be a battery design problem. If I run the system first with both MPPT disconnected then connect the cables into the MPPT it does not send the battery into protection mode and everything seems to go back to normal.

Thanks for the link which I'll check right away for future reference.

I think it's worth remembering what I discovered today because some batteries seem to fe fooled by the MPPT capacitors charging up and interpret that as a short circuit.

Many thanks again

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ejrossouw avatar image ejrossouw logic28 commented ·

My pleasure. The document also explains likely triggers to be considered in conjunction with your other findings. It does however not explain the blown fuse for which the root cause still has to be investigated.

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logic28 avatar image logic28 ejrossouw commented ·

It was very interesting to read but unfortunately I din non find any errors stored, at first because I could not activate the MPPT (I was unsure about pouring it with an external source but thanks to your link I now know it can be done using voltages between 12 &15v) but even now with the unit alive and functioning, I'm not sure where to find the page described in the image and no other messages have been shown or stored as far a s I know but I'll check again on my VRM.screenshot-2024-02-03-at-132817.png

I want to investigate this further as it can be of help for more than just myself

Thanks again

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