subject: What Is A Solar Blocking Diode And Do I Need One? [print this page] So you have seen an advert stating that you need this blocking diode thingy in your solar panel. You may be asking What is a Blocking Diode? and Why dont all panels have them?
I will explain.
With solar panels, particularly 12v solar panels you can use them to charge a battery. Car battery, leisure battery etc.. If you connect a panel directly to the battery the energy will be collected from the sun and go into the battery as electricity. Great! Now the night time comes and the sun goes in. The 12v solar panel is still connected but not generating power. All the energy is in the battery and it wants to escape. The energy flow is now reversed and escapes out through the solar panel.
This is where a blocking diode is used. The diode is able to stop this backwards flow and ensures that the energy collected is safely stored.
Now youre thinking, Brilliant, I will just get a 12v solar panel with a blocking diode!
Hold your horses..
This all sounds great but the reality is not that simple. In all solar installations there are other factors. Very rarely do you simply need to charge a battery that is not connected to anything. You use the battery to run some circuits and electrical equipment. Connecting a panel directly to a battery is not a good idea for many reasons. A charge controller is nearly always recommended.
Connecting directly (even through a diode) can over charge the battery and severely reduce its life. It can allow the battery to become very low and again severely reducing the life. If there are any other circuits on the battery these can affect or be affected by the unprotected panel resulting in a damaged panel or equipment.
Unless you are a trained in electronics always use a charge controller or regulator as it is sometimes referred. When you use a controller a diode is not necessary. This way your existing equipment, batteries and you newly purchased 12v solar panel charger will be protected and give you a long, reliable working life.
One last point, Do not confuse a Blocking Diode with a Bypass Diode
