Backfeeding panels


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mab1
Regular Member

Joined: 10/02/2015
Location: United Kingdom
Posts: 48
Posted: 06:35pm 26 Oct 2020      

interesting that yours is zero - I was a bit surprised that mine's so high TBH - it is possible that the damp has gotten into one of the junctions as i live in a very wet climate - i'll check that out.

Silicone cells always were basically a diode of course, but I assumed the advice of a need for a diode came from the early days on solar when panels did have significant internal leakage - which is partly why those old panels were poor performers - particularly in low light as the output was generated-current minus leakage-current. One of the main improvements in modern cells is a reduction in internal leakage which means they keep generating at voltage down to low light levels.

Whatever the reason, the simple way to check is to connect the panels to the battery it's going to be charging anyway, and when it's dark, open the circuit (at a fuse/ circuit breaker if you don't have a diode like me) and put an ammeter across the break: if the current's negligible, no worries; if it's significant, get yourself a diode.