Blocking Diodes For Solar Panels In Parallel

Now let s consider what happens if one of the panels in the above diagram is shaded.

Blocking diodes for solar panels in parallel.

Blocking diodes are usually included in the construction of solar panels so further blocking diodes are not required. There are two functions a diode can perform in 12volt solar systems either as a blocking diode or as a bypass diode. In short the blocking diodes only provide a single path for current from the solar panel to the battery and block the currents from the battery to the solar cells during night as solar cells are acting as a load instead of generating energy. To prevent this from happening a blocking diode is installed.

It is always installed in series with the solar panel. When a solar panel is shaded the output current reduces dramatically and when it s dark it actually absorbs current. Also we should consider bypass diodes in this. Blocking diodes are used to prevent your batteries from discharging backwards through your solar panels at night.

A solar panel it a grouping of cells in a series parallel configuration of one form or another typically inside a housing. If your panels are a grouping of other panels then you won t need a diode. Mainly we use two kinds of diodes for effective solar panels bypass and blocking diodes. Not only will that panel not be producing any significant power but it will also have a high resistance blocking the flow of power produced by the unshaded panel.

It allows the current to flow from the panel to the battery but blocks the flow in opposite direction. Blocking diodes will be of benefit in any system using solar panels to charge a battery. You may be wondering what is the difference. I was told recently that panels in parallel should have blocking diodes in each branch.

Store bought panels will typically have a protection diode already in place. The blocking diodes are connected in series while the bypass diodes have a parallel connection. Again current flows from high to low voltage so during a sunny day the voltage of a solar panel will be higher than the voltage of a deep cycle battery and the current will naturally flow from the panel to the battery. This is a real problem at night because we could lose all the power we gained during the day.

This would prevent current flowing from one parallel string into a lower current string possibly due to shading and therefore helps minimize mismatch losses in parallel connected arrays. I recall reading somewhere that one should also install a blocking diode for each parallel string.