Hi, Dumb question: I have 3x 305W blue solar panels, 1.5 yr old, last year I regularly got 700 to 800W going via the MPPT into my 2x 200ah LifePo4 batteries. This year, same period, similar sun conditions, clean panels never over 600W… Batteries are not full, would this mean 1 panel is defective? Thank you, Pieter

Thank you, the wiring looks good so I’m getting a replacement panel through warranty, will report back once installed to conform this (hopefully) resolved the issue! May take a while as friends are bringing it on their boat..

You are certainly correct on the conditions but am on the med and been monitoring for a month and really seems like I get 30% less, need the juice… Is there a way to test for a faulty diode? PS no shade or dirt, on a boat.

Like I said, if the panels are fully illuminated, without shades, then the diodes are not the problem. Do you have some references from last year? Is the total production voltage the same? Is the current the same? If the current is the same but the voltage lower, then there is a problem with a section. If the current is lower but the same voltage, then is a problem with transparency/wear.

[IMG_20250517_094908997_AE] [IMG_20250517_094931887_AE] [IMG_20250517_094845065_HDR_AE] This was 2024

[Screenshot_20250520-153433.VictronConnect] And now, same period

I am going to assume you have 3 panels in parallel. You could have one panel failing or a poor connector on one panel. A quick test if you can access the panels is get a sheet of cardboard or a thick blanket. Then cover the panels one at a time, if you cover one and the power stays the same then that panel or the connectors are not making contact.

[image] A call to all panel experts and installers - checklist for checking arrays DIY It seems to me that it would be easier to help users with problems if we had a standardised list of array checks we could point users to. For computer issues (my previous occupation a lifetime ago) there are a number of forums where they point users to a standardised bunch of commands they can run which collect all the data that answers almost all the forum expert’s questions. The forum experts won’t touch a user’s issue unless they have attempted to collect that info, and it really cuts down on…

A tester for up to 1600w costs around 75€. Always good to have something like this in your toolbox. But a blanket shadowing single panels works too.

Right, easy peasy, my middle panel doesn’t do anything✔️ Thank you gentlemen, much appreciated!

Now to work out if it is the panel, or wiring or connectors.

I’m seeing a voltage drop of .72v and .49v between the mppt and BMV in the first 2 photos. That amount of voltage drop requires investigation, and if possible rectification.

Solar panel performance worsening

DIY

pwfarnell 20 May 2025 14:36 8

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Solar panel performance worsening

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