Six-year-old SmartSolar MPPT 100/20 misreading battery voltage

Q&A and troubleshooting
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1

Hello,
We have a small off-grid system with 2x100w solar panels, SmartSolar MPPT 100/20 and now 2*Lead Carbon 12v batteries in parallel (Expedition Plus EX12-160C). All has worked well for about 6 years, but this year we have had many unexpected load switch-offs. Initially we thought it was a problem with the old batteries, but having replaced those we are still getting the effect. Looking at the battery voltage information in the app, the voltage seems to “bounce” low then back up again every time a light (LED strip, up to 1A load) is switched on. See screenshot 175101 for example.

Screenshot_20241122-175101
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Further, we have a separate voltmeter across the battery, which was reading around 12.7V while the trends in the app were showing around 11.3V. “Rebooting” the controller (disconnecting from all power for 10 minutes) fixed this and also fixed the “bouncing” issue.
Screenshot_20241122-185700
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So, am I correct in assuming that the controller is going faulty and should be replaced? Is this a known failure mode?
Any advice on which controller to choose would be appreciated - I sized the original around the solar panels; but now we are interested in possibly adding wind generation, so there would be two different inputs - would that need a different type of controller?
Thank you

2

A wind generator should have its own controller, that won’t be anything to do with the solar controller.
Would suggest checking all your wiring and connections between the solar controller and the battery, making sure that the wiring is the correct type, appropriate gauge for the current and round-trip distance, and the fuse or breaker between the controller and battery, as a simple loose connection or degraded/offbrand fuse or breaker could be causing what you’re seeing.

3

And corrosion.

4

Thank you for the helpful suggestions. I will investigate particularly the breaker next time we visit. Corrosion is a strong possibility as the chalet gets quite damp at times in winter.
I will check the other connections - wiring type gauge etc. should be fine as I designed the system around the current capacities. (Might have to change them if we do add wind, but that is another story.)