Hi all, after a misshappening where the solar panel got short circuit, the MPPT now got power at the PV port even though no panel is connected (measured ~11,97V @midnight with multi-meter and Victron app). Before this happened the PV shows 0V when no power is coming from the panel. Now at day time, panel connected the MPPT do charge the battery, so it seems to be working but the voltage at the port with no panel connected gets me confused and wonder. It is not correct.
Is the MPPT shot or is there a solution for this?
The diode inside high FET is making it possible to have at the MPPT port the battery voltage minus up to 0.7V.
So, based on an educated guess, without having the exact schematic, yes, it’s possible.
If they have a schottky barrier between the panels and the FET, then, normally this is not possible, but if following an incident the schottky barrier is damaged and shorted, then yes, now it’s possible, of course the MPPT could work as usual.
@alexpescaru - Thanks for answer. I will see if I can get hold of an Bench Power to do the FET test (12V/0.5A), but it sounds exactly as it is the FET on your description. The panel is only an 109W so, I believe, there should not be too much open circuit PV or too much PV polarity short circuit to kill the FET. But anything can happen.
My worries are, can the panel get damaged when you put in voltage into the panel and not out of it? I mean as it is now I put in, as you say, almost the same as in the battery (0.4V lower).
I didn’t say the FET is damaged… If it would be, the MPPT will not function anymore.
I said thay the input Schottky barrier could be the culprit of what you’ve said.
And yes, it’s better to have the power flowing in just the right direction.
For reference, a similar schematic below, where the diode inside Q1 could allow the battery voltage to flow to the panels, but D1 is blocking it. If D1 is shorted, then the battery voltage could reach the PV input.
@alexpescaru - Thanks for clarifying, I misread your post.
@lxonline - Yes, thanks I have used it but I do not have an Bench Power so I have been using an ordinary power supply 12V 500mA and do not know if that is reliable enough. In section #7 I need 24V and I do not have any supply for that. But up to that point all is well with the MPPT. Except for the problem stated in the first post.