Monthly Archives: October 2019

Solar Breakdown

With several trips planned over the summer, and due to the fact that it’s really too darned hot to use the boat much in July and August anyway, we thought it would be prudent to strip the solar panels off our bimini. That way, if some tropical weather developed while we were off elsewhere, it would be one less thing to worry about.

(If you haven’t been around long enough too have read the original post from back when we designed and installed our solar charging system, here it is:  Our Vision Realized)

One advantage of flexible solar panels is that it’s not a major task to remove them and pack them away. Disconnect the wiring connections and release the fasteners holding them to the bimini, and you can just slide them off and store them below. It doesn’t even require any tools. But when I started taking things apart, I discovered a very unpleasant fact. The system I’d designed used several rigid MC4 adapters to electrically combine the panels. And almost every one of them had failed in some way.

Here’s a 3-to-1 combiner I removed. You can clearly see that the left leg is cracked and failing, the center one is more or less OK, but the right one has broken off completely.

This was typical of all the combiners I removed. Nothing was holding a lot of these wiring connections together except friction.

Once I pulled everything apart, I made a small pile of everything in the system that had failed in some way.  Amazingly, the system was still working fine, but a good tug on many of the panel leads would have pulled them completely loose from these broken combiners.

The majority of these parts were tucked into pockets in the bimini, so I know UV exposure wasn’t the problem. Either they got brittle and delicate in their four years of use, or some sort of stress, possibly caused by the bimini flexing in the wind, was breaking them.

I scratched my head a bit and thought about a solution. The system I designed needs these combiners to tie our six solar panels together in the series/parallel circuit I’d layed out. They’re pretty important parts. But I didn’t want to just replace them with more of the same now that I saw such a high failure rate.

Fortunately, some research turned up a solution. Rather than rigid combiners, I found that they also make these MC4 pigtails. The piece on the right is a direct replacement for the old one on the left below.

I’m thinking these pigtail-type combiners will be a lot more forgiving of twists and torques than the old ones were. I ordered enough to replace all the existing connectors.

We don’t have a lot of travel planned between now and the end of hurricane season, and it’s finally cooling down enough to start spending some time out on the water again , so we recently re-assembled our solar system using these new parts. Everything snapped together fine, and seems to be working well. Check back in a few years for an update on how these new parts hold up!

In the meantime, if you happen to be designing and installing your own solar charging system, you might want to consider the type of MC4 combiner to use. I just can’t recommend the rigid ones for marine use.