I am new to this forum and looking for any guidance from others more experienced than myself.
Our folding 100W panel (2 x50W in parallel) recently stopped maintaining the charge on our 110Ah sealed lead/acid leisure battery. Investigation suggested that the charge controller stopped working once it and the panels became warm.
I have disconnected the integrated PWM controller and replaced it with a Victron Smartsolar 75/10 MPPT controller installed inside the van. The new controller is working but the solar parameters reported by the Victron Connect are not what I expected.
The data label on the panel states that: Voc = 21.6V, Vmp = 17.5V, Isc = 6.17A (2 x 3.08A) and Imp = 5.71A (2 x 2.85A) @ STC
In bright late-morning sunshine on the South coast the Connect app Status screen displays the solar panel voltage as 21.33V and the battery in Absorption charging phase. This value was also checked independently using a digital voltmeter at the rear of the panel and is correct. The panel current was only 1.7A.
The Connect app History shows the maximum panel voltage as 21.42V. Not clear if that is a measured or calculated value
The solar voltage displayed on the Status screen is higher than the stated Vmp @ STC on the panel data label and the solar current was lower than I expected when in Absorption stage. See screen shots
I am wondering if the previous failure maintain the leisure battery might be caused by more than just original charge controller and perhaps one of the panels has failed, possibly open circuit.
Why is the solar panel voltage in hot late-morning sunshine significantly higher than Vmp @ STC when I understood it would be lower under real conditions. It is almost approaching Voc taking temperature effects into account?
Would one of the parallel panels failing explain the results experienced?
All comments gratefully received.
