MPPT Solar Controller

[sailorboy1]

Why do some made it so hard? Oh well, back to the basement.

[skipgundlach]

Originally Posted by Jon Hacking

snip...

If you're trying to control 60A, you've got multiple panels. Running them in parallel means that if one gets even a little shaded, it won't be able to reach the MPPV of the other strings, so it will simply drop out of production. But if each series string of panels is feeding its own MPPT, then such a drop in voltage can still contribute meaningful current to your batteries. And multiple small MPPTs is often cheaper than a single large one (certainly was in my case).

snip...

I don't have any issue with multiple controllers, other than that if you're retrofitting, you might have to do some rewiring - which might be challenging.

However in extensive conversations with the tech guy at Blue Sky (mentioned up-thread) he recommended the cure for parallel issues like that by insertion of a blocking diode into the MC4 stream positive legs.

From my correspondence of the time:

couple interesting articles:

http://www.electronics-tutorials.ws/...ss-diodes.html

https://www.altestore.com/blog/2016/...-solar-panels/

and...

Here is an article about combining multiple panels, although it does not mention blocking diodes in particular, notice what happens when you combine multiple panels in parallel with different voltages:

Connecting Solar Panels Together to Increase an Arrays Power

So, I did that; My positive legs have the diode inline before the parallel junction for the two panels (360W Sunpowers). I don't actually have shading issues, but it can't hurt in the event my KISS wind generator MIGHT shadow some of the lines of cells enough to make a difference...

[noelex 77]

Blocking diodes are not often beneficial in a marine installation. You can easily measure the current discharge through the solar panel in your system and estimate the power loss/gain of installing blocking diodes. Usually they will produce a (small) net loss.

The exception is if the solar controller does not incorporate a blocking function at night (or you have no controller), but this is rare for modern controllers.

A blocking diode cannot correct the voltage mismatch between panels that are subject to different conditions such as shade, and this is the mechanism behind the major performance benefit of fitting multiple controllers.

[sailorboy1]

Originally Posted by sailorboy1

a burned up MC4 connection on the GROUND common line at the panels

i was depressed when I made the post and met to write that it was a burned connection on the negative line

[ttex]

I have run into the siuation where a wire hangs on by a thread and when tested it will show the volts you are looking for but it wont carry any amperage and the appliance wont work.

Classic.

[Maine Sail]

That image is a prime example of why we do not and will not use any MC4 connector that is not a genuine Multi-Contact by Stäubli. We've seen far too many counterfeit MC4's fail.

Originally Posted by sailorboy1

Here it is, the best opening ever provided for trolls.

Installed the new controller (exact replacement) and it had the same problem. This started a slow piece by piece review and inspection and isolation of every wire and connection in the system. On the second pass of connecting and disconnecting stuff i found it, a burned up MC4 connection on the GROUND common line at the panels (that worked on one isolation go through but didn't the next go).

Since there was voltage at the controller from the panel I never suspected a wire problem. My thinking was that if there was voltage there was a connection that would carry at least some current (the problem was that no current was flowing through the controller). The Outback tech also thought the same.

[noelex 77]

Originally Posted by ttex

I have run into the siuation where a wire hangs on by a thread and when tested it will show the volts you are looking for but it wont carry any amperage and the appliance wont work.

This is a common problem. Modern multimeters are in many ways excellent at measuring voltage accurately because they have a very high input impedence, often in the Gigaohms range, but this same feature leads to mistakes unless you understand what you are measuring. It can mislead even the experienced.

Especially if a wiring/connection problem is suspected, always test voltage under load wherever this is feasible.

The “old timers” often used a test light rather than a multimeter to detect the presence of voltage and while not foolproof this technique can still be useful on occasions.