Blocking Diodes For Solar Panels In Parallel

When a solar panel is shaded the output current reduces dramatically and when it s dark it actually absorbs current.

Blocking diodes for solar panels in parallel.

If your panels are a grouping of other panels then you won t need a diode. The blocking diodes are connected in series while the bypass diodes have a parallel connection. Blocking diodes are used to prevent your batteries from discharging backwards through your solar panels at night. 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. To prevent this from happening a blocking diode is installed. Store bought panels will typically have a protection diode already in place. Also we should consider bypass diodes in this.

A solar panel it a grouping of cells in a series parallel configuration of one form or another typically inside a housing. It is always installed in series with the solar panel. You may be wondering what is the difference. This is to prevent current flow from branches in high sunlight feeding current into those in shadow.

Now let s consider what happens if one of the panels in the above diagram is shaded. There is a possibility of the current flowing from the battery to the solar panel thereby discharging the battery overnight. It allows the current to flow from the panel to the battery but blocks the flow in opposite direction. Blocking diodes are usually included in the construction of solar panels so further blocking diodes are not required.

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. Blocking diodes will be of benefit in any system using solar panels to charge a battery. 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. There are two functions a diode can perform in 12volt solar systems either as a blocking diode or as a bypass diode.

This is a real problem at night because we could lose all the power we gained during the day. I recall reading somewhere that one should also install a blocking diode for each parallel string.