Why Do I Need Blocking Diodes For Solar Panels

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.

Why do i need blocking diodes for solar panels.

Blocking diodes are usually included in the construction of solar panels so further blocking diodes are not required. 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. The energy flow is now reversed and escapes out through the solar panel. Now let s consider what happens if one of the panels in the above diagram is shaded.

Not only will that panel not be producing any significant power but it will also have a high resistance blocking the flow of. If you have two 175 watt panels each at 42 volts you will need two 8 amp 45 volt diodes. Now you re thinking brilliant i will just get a 12v solar panel blocking diode hold your horses. The diode is able to stop this backwards flow and ensures that the energy collected is safely stored.

Nowadays most solar power systems have a charge controller between the solar panel and the battery and this charge controller prevents this backflow of electricity eliminating the need for a blocking diode. If you have multiple parallel strings of solar panels that get shaded at different times a blocking diode in series will help prevent the power from the sunny string being forced back up through the shaded string. 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. This is common on sailboats with a solar panel on both the port and the starboard sides.