Reverse Current Flow In Solar Panels

Many older books and articles recommend using blocking diodes to prevent reverse current flow back through the panel at night dark current many others do not including us mostly.

Reverse current flow in solar panels.

In the junction box are bypass diodes so that if one or more of the cells on the panel become shaded the full current of the rest of the enlightened panel will not be applied to the reverse biased shaded cells. 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. Thus this allows us to effectively provide solar battery charging with reverse current protection. So we demonstrate this concept by using a mini solar panel to charge a rechargeable pencil cell battery.

The combination of distributed energy storage and distributed solar is reversing the power flow allowing customers and communities to generate most of their energy at home or nearby. Also we use a charge control circuit designed to stop reverse current flow and charge the battery effectively using the solar panel. Some solar panels are actually two or more panels wired in parallel inside a common frame. The internal diode structure of the solar cells causes reverse current to flow through the faulty generator string that depending on the strength of the current may lead to excessive heating or destruction of the modules in this string.

With a small 6v solar panel the losses in the diode would exceed the power which would have been lost. It actually depends on the situation but as a general rule in 12 volt systems you will lose more power from diode losses than you will from leakage back into. Depending on the source of the power this reverse flow may be intentional or unintentional. It is often recommended that a diode be fitted to prevent reverse current flow back through a pv solar panel at night time dark current as current passes through a diode there is a voltage drop with power lost as heat.

Backfeeding is the flow of electric power in the reverse direction of the generally understood or typical flow of power. 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. In some circumstances these electrical faults in solar panels lead to current being forced in the wrong direction through a string of pv modules. Solar panels reverse current issues green power operate a dedicated solar service and maintenance division which often finds electrical faults in pv systems.

If not prevented in the case of unintentional backfeeding or properly installed in cases of intentional backfeeding backfeeding may present unanticipated hazards to electrical. Blocking diodes will be of benefit in any system using solar panels to charge a battery.