Backfeeding panels

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Murphy's friend

Regular Member

Joined: 04/10/2019
Location: Australia
Posts: 83
Posted: 09:43am 27 Oct 2020      

I have several 2 & 4 panel strings feeding my 60A outback MPPT regulator. Battery voltage is 48v nominal.
As the panels are only matched within a string but there are several different type of panel (many second hand) I noticed there was current flowing from one string to another when the MPPT went to sleep due battery being full. Each string has its own analog Amp meter BTW.
So I fitted 10A Schottky diodes at each string output to the MPPT. Voltage rating of the diodes is a bit more than the string open circuit voltage.
The TO 220 type diodes are on a heat sink. They get quite hot when a full charge of maybe 50A+ flows into the battery.

No more funny currents between the strings.