Blocking diode in a solar panel is used to prevent the batteries from draining or discharging back through the pv cells inside the solar panel as they acts as load in night or in case of fully covered sky by clouds etc.
Install a blocking diode solar panel.
In short as diode only passes current in one direction so the current from solar panels flows forward biased to the battery and blocks from the battery to the solar panel.
If you have two 175 watt panels each at 42 volts you will need two 8 amp 45 volt diodes.
Blocking diodes are usually included in the construction of solar panels so further blocking diodes are not required.
This video shows how to install a diode to any solar panel to prevent discharging.
Learn how and why blocking diodes and bypass diodes are used.
Now let s consider what happens if one of the panels in the above diagram is shaded.
Blocking diodes installation instructions sm 335 issue c 03 11 05 marlec engineering co ltd blocking diodes a blocking diode is required in each series string of solar modules between the modules and regulator battery to prevent current flowing back through the modules when the modules are shaded or during darkness.
For solar panels we recommend you put one blocking diode on each solar panel inside an abs project box the diode needs to have a voltage and amperage rating above that of the panel.
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Blocking diodes will be of benefit in any system using solar panels to charge a battery.
In simplest terms a diode can be understood as a two terminal electronic device which allows electrical current to pass in one direction.