Wiring Schematic diagram

Any diode-based circuit that safeguards against  supply polarity reversal brings about a certain voltage drop. The following post shows a zero drop diode equivalent circuit which can specifically become useful for solar charger applications.

Solar panels as we all know may heavily depend on the position of the sun and its rays intensity. Under overcast conditions the solar panel strength also deteriorates and its voltage drops. A diode is normally associated  with solar panels for preventing accidental reverse connection, however a rectifier diode or even other forms of diodes also drop some voltage across them which might become crucial during bad sun light conditions.

The discussed circuit of a zero drop diode circuit effectively handles the above situation.

Additionally, in case relatively higher currents are associated, the employment of an applicable diode, and its dissipation, can pose problems.

This circuit employs a relay contact to disconnect the positive supply  whenever the input voltage is rendered the wrong polarity. The coil voltage of the relay can be selected to be lower than the input voltage, since Re is triggered within a few milliseconds, and subsequently acquires the correct coil voltage through T1-D1.

As the sustaining voltage of a relay is ususally below than the switching voltage, D2 can be calculated such that the relay triggers optimally with a lowest of zener current consumed from the supply.