One last blocking diode question

[GlennDale]

I keep getting feedback concerning blocking diodes on another forum. I can not locate panels that match my ordinal pair so I have to install a new panel panel string that is close. One pair is has a VOC of 21.4 volts and producing 5.5 amps. The second string has a VOC of 5.38 amps and producing 5.38 amps. These panels will lay flat on the top of my RVs. This rig spends most of its time at 40 + degrees north. I was told on this forum that I will get 50% production at best under these conditions. Am I making a mistake or is this feed back on diodes that I am getting important?

 

[n2aws]

I keep getting feedback concerning blocking diodes on another forum. I can not locate panels that match my ordinal pair so I have to install a new panel panel string that is close. One pair is has a VOC of 21.4 volts and producing 5.5 amps. The second string has a VOC of 5.38 amps and producing 5.38 amps. These panels will lay flat on the top of my RVs. This rig spends most of its time at 40 + degrees north. I was told on this forum that I will get 50% production at best under these conditions. Am I making a mistake or is this feed back on diodes that I am getting important?

I'm interested in this too. I keep reading and hearing mixed info on this topic.

One thing you can always do, is try them in parallel and see how the production is, and if it's not good, get a second charge controller, and wire the second array into the second SCC.

Either way, I'm following the conversation!

 

[efficientPV]

Solar panels are just a buch of crappy diodes in series. When I started out they were really crappy, you could actually see burn homes in some cells. There was some leakage and blocking diodes were installed to prevent draining battery. You can backfeed power into a solar panel. It is just like powering an string of diodes, you have to go over the forward voltage of each cell times the number of cells. This voltage is higher than the open circuit voltage so other panels in parallel just don't absorb power. This is all theoretical. I have six parallel strings which see heavy shading and I'm thinking about installing some blocking diodes. The reason is lightning. I've had several events and you can see visual damage to the cells. Some of these panels could fail in the future and start absorbing some power that I just might not notice. That has been on my to do list for years along with adding some lightning protection. I've taken a direct hit and it wasn't a big deal. I f buying used panels it might be worth considering. They do lower power slightly and that would be a big consideration with low voltage 12V panels.

 

[mikefitz]

This rig spends most of its time at 40 + degrees north. I was told on this forum that I will get 50% production at best under these conditions. Am I making a mistake or is this feed back on diodes that I am getting important?

You panel strings when connected in parallel will work fine , you dont need blocking diodes.
I am touring in a RV at the moment at 50 deg North and with sunshine I am seeing a maximum around 70 % of rated panel power, mounted flat on the roof. ( Victron solar controller)