Mottled shade on solar panels not good?

When in the storage facility I cover my camper with a fairly heavy duty cover and if I had to quantify the loss of voltage I'm getting from the panels I would place it at only 50% maybe even less.

Ron W.

That is the issue I had seen something about. My panels are Canadian Solar that I believe have three bypass diodes in each panel. So I am going to assume I’m okay.

bpounds,

Nice link. Thanks!

This explains the theory of a hot PV cell. In practice, it isn't really a concern. But maybe this is what you've seen referenced.

Shade on solar cell

So diodes are not damaged by repeated partial shade. Great. I have a Morningstar mppt controller but I had to go parallel on my three 315 watt panels because of the voltage cap if in series being exceeded when the panels would first get light. By the way, I had my first opportunity this last week to truly drycamp depending on the solar array to keep my residential fridge running. Despite continued cloudy skies, it worked like a champ.

With no shading, I had my three 100w panels in parallel with MPPT and also tried with them in series with the MPPT. Made absolutely no difference to amps to the battery in full sun.

With shade coming in where the shadow from the trailer (ground mounted solar) started across the array from one end late in the day, I started to lose amps to the battery.

I chose to be in parallel for that, since I kept more amps coming in from the remaining part of the array, whereas being in series meant losing more sooner. The shadow was at an angle somewhat moving across, so it might have been a race between what diodes could do for you and what keeping unaffected panels going does for you. You still have diodes in an affected panel even when in parallel of course.

Perhaps it is another of those things that "depends".

mike-s my controller can not deal with more than 50 volts input. It is a Blue Sky 3024di which was, at the time, top of the line. When panels are new their output may be a bit higher--I would not trust it to have 2 24 volt panels in series.

pianotuna wrote:
Unless the panels are 24 volts or higher--then MPPT is a good path to follow.

So, why would you put multiple 24 V panels in parallel rather than series through an MPPT controller (other than a crappy one which couldn't handle 48V)?

mike-s wrote:

BFL13 wrote:
I see what you mean, but if your example started with the two 12v panels in parallel with an MPPT controller, then the type of controller would be the same in each case.

Not much point paying for MPPT then using parallel panels, though. I was talking about common, real world systems.

Yes, but the wording seemed to suggest the cause was the controller type and I just wanted to make that go away and leave the reasons as you meant, which I hope is now all clear.

mike-s,

Unless the panels are 24 volts or higher--then MPPT is a good path to follow.