I have two series strings with two100 watt panels in each string. These two strings placed are in parallel with each other. I had a comment that I need to insert blacking diodes in this array. In all my reading I have not come across blocking diodes. First I am hearing of this. Did I mess something somewhere. Feedback would be appreciated. Thanks
Blocking Diodes?
- Thread starter GlennDale
- Start date
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
Blocking Diodes were first used when we had systems with panels hooked directly to the batteries. In this situation, the panels would drain the batteries at not.
With more modern MPPT charge controllers, there was a belief that if the strings did not get equal sun the shaded string would have a back-current from the non-shaded string. However, it turns out to be a non-issue. A panel will generate almost full Voc with very little sun. Consequently, the shaded string won't contribute power, but the voltage it generates will prevent back-feed. Meanwhile, if there is a blocking diode, it will cause a power loss when the current is flowing.... so it tends to be a net loss of power.
With more modern MPPT charge controllers, there was a belief that if the strings did not get equal sun the shaded string would have a back-current from the non-shaded string. However, it turns out to be a non-issue. A panel will generate almost full Voc with very little sun. Consequently, the shaded string won't contribute power, but the voltage it generates will prevent back-feed. Meanwhile, if there is a blocking diode, it will cause a power loss when the current is flowing.... so it tends to be a net loss of power.
