Solar Panel Bypass Diodes - Are They Really Needed?

With a large batch of solar panels that had shorted diodes comes a bootcamp on their importance. I go through their effects on performance of the panels and if the solar panel will work without them!

[@douggolde7582]

Active bypass diodes were developed and offered by Microsemi, STMicroelectronics, and Texas Instruments about a decade ago. They offer higher efficiency and are more robust against lightening strikes. Unfortunately they cost about 10 cents more so panel manufacturers didn't use them.

[@ericphantri96734]

Can an acceleration circuit extract more heat out so extract more under low sun heat . that indicated low efficient wiring also remember the airforce always analyze most panel before each change maybe that is why the cell used by airforce affect more than the rest

[@Broxine]

Thanks. Very helpful comparsion 👍

[@ruanjiayang]

4:02 seems strange. Without bypass diodes, the current has to flow through the shaded cell (≈ 0 watt)， why decreasing the voltage could restore some of the power?

[@Fourthbean]

I’m not sure, my theory is that part of the load is back feeding the dead section of the panel and part is being used to generate usable power. So if it’s split between the two uses the voltage drops?

[@ruanjiayang]

@@Fourthbean The phenomenon is quite similar to that of panel with good diodes. Could you please provide details on how your system setup, so that I can replicate this in my software simulation.

[@rcinfla9017]

A shaded cell can develope a high reverse voltage fed from unshaded cells. If the shaded cell has a relatively low resistance shunt defect spot (all cells have some defects of varying severity) the high reverse voltage can creating a very hot spot that can damage the panel, or even start a fire. Bypass diodes are primarily for safety to limit the maximum shaded reverse voltage on any cell.

[@ruanjiayang]

@@rcinfla9017 Right. I figured it out. The inverter was decreasing the voltage to find the new MPPT point, in order to make the bypass diode activated.

[@shofarsogood7504]

Do bypass and blocking diodes refer to and do the same thing?

[@BeeneEnergy]

They are the same component, these are called bypass diodes due to the function they are performing.

[@shofarsogood7504]

Beene Energy thank you for the help.

[@liberdad8610]

As to the function the diodes perform, a blocking diode prevents reverse current from flowing backwards through the whole panel typically when its dark and there is no forward bias occurring in the solar cells. Most solar panels do not have diodes installed with this blocking function configured as that functionality is primarily handled by the charge controller. This video shows how the diodes function when used in a bypass arrangement and it does a most excellent job of that!

[@rcinfla9017]

With charge controller use, there is no reason to add blocking diodes in series with panel(s). Charge controller disconnects from batteries at night (or when PV output drops below level necessary to run charge controller)
Panels or strings of panels in parallel will have some leakage when one of the parallel strings are shaded. Putting blocking diodes on each of the parallel strings to prevent leakage down a shaded parallel string will prevent the leakage during shading but the net W-hr loss saved during shading periods is usually much less than the alway-in blocking diode W-hr loss of the series blocking diodes If the leakage of the shaded parallel string is large enough it can effect the operating point selected by MPPT controller that can reduce the output of unshaded panels. Again, the loss depends on how long the shading lasts and should be weighed against the 100% of time, always-in loss, of adding blocking diodes (roughly 5 watt loss per blocking diode, depending on panel current output).
Parallelled panels or parallelled strings need to be well matched panels or MPPT controller will not achieve optimum operating point and all panels will produce reduced output.

[@douggolde7582]

Blocking diodes are used when paralleling strings.

[@sammyd7857]

The solar cells are like a photo transistor. If a whole cell circuit is shaded it will block the current in the whole system

[@douggolde7582]

A shaded cell will block current until the reverse bias avalanche voltage is reached, about 30V. This is why you get hot spots and roof fires.

[@brantgoose]

Still confused about the wiring of the diodes

[@Alihaj1984]

I removed all diodes from my solar panels from 4months ago , Now it work perfectly without anything mistakes

[@BeeneEnergy]

Just watch out for partial shading issues. Specifically dirty panels that block part of the cell. It could cause back feeding of cells and lots of heat. Possibly enough to burn the back sheet.
Stuff I’ve learned since posting this video :).

[@Alihaj1984]

@@BeeneEnergy
Thanks, every week I clean the panel from dust

[@rcinfla9017]

You may get hot spots that destroy panel or even catch fire.

[@surenbono6063]

..why not do bypass diodes on every single cells instead?

[@BeeneEnergy]

I imagine cost is the primary factor.

[@surenbono6063]

@@BeeneEnergy Reason no 2: How you gonna place it under each cells ? Circuit board style?..they should make each cells replaceable in the future..

[@ericphantri96734]

How did you look like President Lincoln ? Did you remember

[@fritzb.5921]

"biode"

[@sempertard]

bypass diode fool !!! :)