Bypass Diodes Needed for individual panels?

 I've done searches on this and have not come up with anything conclusive.
I'm upgrading my system from 12v to 24v and I have the following.
  4 100w "12v" panels that will be configured as 2 in series, and then the 2 groups of 2, in parallel. I believe this configuration will provide a balance between available charging, and redundancy if one of the panels is damaged or temporarily shaded.
 My mppt unit is a 4215bn epever going to two agm 12v Batts in series.

question is:

Do I need a bypass diode at each panel (4 total) to bypass the overall panel in the case where 1 is damaged, shaded or develops some other fault? Or do the bypass diodes in each panel accomplish this in addition to protecting sections on internal cells? Diodes are cheap enough but I don't want to add additional points of failure if they are not needed.

Thanks in advance

Good question. As far as I know the bypass diodes already in the panel are all you need. I thought most panels come with them. Correct me if Im mistaken. I have a 24 volt system with 12 volt panels in series.

Unless the panels are defective the diodes are already installed so hooking them in series should give you the 24 volts you need...

Not all panels on the market come with blocking diodes or bypass diodes or their original name schottky diode.

The primary thing to understand is how to SIZE this type of specialized diode for each panel.  Not only to size the rating needed, but, to keep the system balanced, each wire set from each panel needs to be the SAME length.   WHY the same length?  Should a failure happen, any overload would go evenly to the other panels and those diodes can take the hit in a balanced fashion.  Uneven lines would allow the closest diode to take the brunt, and possible it too would fail.  Thus, your repair costs would more than double.

A blocking diode is like a a surge protector by blocking the back-flow of the current.  BUT, there isn't a reset button.  lol

Now, if one also had in the system FAIL-SAFE diodes, life would be nicer.