How to Fix Portable Solar Panels 

Monday 15th June 2020 
by Matt 
 
How to Fix Portable Solar Panels

Here's how I diagnosed and fixed two broken solar panels with basic tools in under half an hour.

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Introduction

Whether you're a recreational camper or a full-time RVer like us, portable solar panels (also known as a solar suitcase) can be a great way to get an off-grid power boost without firing up a generator.

When we first hit the road, we had no rooftop solar panels and we relied solely on a 100W portable solar panel.

RV Solar: Part 2 - Renogy 100W Portable Solar Panel

Buying a portable solar panel can be the easiest and quickest way to get started, but there are some things you should know first.

RV Solar: Part 2 - Renogy 100W Portable Solar Panel

But as with anything, they can break. Not only can they be quite expensive, but you might be left without power! Fortunately, with just some basic tools and a little know-how, the fix may be easier than you think.

We've been staying with our friend Cortni up near Boise, ID, the mastermind behind The Flipping Nomad. Although her rig has lots of rooftop solar panels, she also has a couple of portable panels, and while we were here she asked if I could take a look at two of them that were broken.

A while back I built a DIY 200W portable solar panel and I know a little bit about solar panels so of course I said yes!

DIY Portable Solar Panel

A portable folding suitcase solar panel is one of the easiest ways to get started with solar, but they can be very expensive - so we built our own for half the price!

DIY Portable Solar Panel

Both of Cortni's solar panels were Renogy 100W Solar Suitcases with 20A Voyager Charge Controller. One was half working, and the other had stopped working entirely after being damaged during strong winds.

Loose Connection

Solar suitcases are made of two individual panels, hinged in the middle. The two panels are usually then connected to a charge controller that can be connected to a 12V battery.

The first panel I looked at was half working. Literally. One of the panels was producing power and the other was not - easily tested by covering one panel in turn and seeing how much current was being registered on the charge controller screen on the back.

Since neither panel appeared physically damaged on the front, my suspicion fell to the wiring. On the back of each individual panel is a junction box, easily opened by depressing the tabs with a screwdriver. Inside is a bypass diode, and the connections between the solar cell array and the pigtail wires.

Renogy 100W Solar Panel
In total I was only seeing about 1.8A, and it dropped to zero if I covered the left panel.

As I suspected, one of the connections (the positive side) had come loose. I've seen (and fixed) this on another friend's solar panel in the past, and while I think it's an entirely avoidable quality issue, fortunately the fix is simple. I confirmed the issue by pressing down the connection with the probe of my digital multimeter and watching the output of the charge controller double as the panel came to energized.

Renogy Voyager Charge Controller
Just pressing down on the connection restored power from the second panel, doubling the output.

I disconnected the panel from the battery and propped it up on a table. I confirmed the issue once again by checking for continuity between the two sides of the connection - as expected, nothing.

Loose Solar Panel Connection
These two sections should be connected, but the multimeter shows infinite resistance.

The fix was as simple as soldering the connection - I was generous with the solder all around the connection to ensure it holds.

Personally, I use a Hakko FX888D temperature-controlled soldering station with 60-40 rosin core solder. You'll just need to take your time and make sure your soldering iron (or soldering gun) can get hot enough as the metal terminals will dissipate heat pretty quickly.

After soldering, I checked again for continuity, and it all looked good.

Soldered Connection
With the connection soldered, we now see 0Ω - in other words, they're connected!

I closed up the junction box, careful to ensure the O-ring was seated correctly, and connected the panel back to my battery to test. When placed in full sun, the suitcase was producing output from both panels - easily confirmed by shading each one in turn.

Voyager Solar Charge Controller
The panel is working again! The output is higher because of the orientation of the panel.

I'm not sure what caused the connection to come loose. There were no signs of damage on the outside of the junction box and no signs of thermal damage inside. My best guess is that it's just vibration and heavy use over time causing a weak connection to fail.

Loose connections can be dangerous, but fortunately it's an easy fix.

MC4 Connectors

If the first one was an easy fix, the second was even easier.

The panel had blown over in strong winds, and had tugged violently on the electrical cable, damaging the inline MC4 connectors between the panel and the battery. Looking inside the MC4 connectors, the damage was visible.

If the charge controller isn't connected to a battery then it won't show any current, and the damaged MC4 connectors were completely breaking the contact.

The MC4 connectors join the panel to a pair of battery clamps, and needed to be replaced or removed. The heat-shrink around the cable was starting to tear as well.

MC4 Connectors
These connectors were damaged internally, and the protective sleeving was beginning to tear.

With an MC4 crimping tool and new connectors, it's not too hard to replace them. However, we had neither the tool nor new connectors, and since Cortni didn't need to connect the panels to anything else, we agreed that the simplest course of action was to simply cut the MC4 connectors off and splice the wires together.

Normally I prefer to use adhesive-lined heat-shrink butt splice connectors, but I had run out, so instead I used regular butt splice connectors, easily crimped on by hand.

Butt Splice Connectors
Hand crimped butt splice connectors.

Since it was for an exposed, outdoor location that would potentially be subject to lots of flexing and mechanical stress, I decided to go a little overboard with adhesive-lined heat-shrink tubing. First, I put some new adhesive-lined heat-shrink tubing over the torn sections.

Then I put some more over each end of the butt splices.

Heat Shrink Tubing
Adhesive lined heat shrink tubing over the ends.

Then a long piece over the entire splice.

Waterproof Connection
This should keep water out!

And lastly, finished it off with some automotive wiring harnesss cloth tape (I love this stuff) to give it an extra layer of protection.

Automotive Wiring Harness Cloth Tape
OK, this wasn't necessary - but it should help protect the joint.

Overkill? Almost certainly. Even though the butt splice crimps should be mechanically secure on their own, I wanted to ensure the join was as strong as possible and completely weatherproof.

I connected the panel up to my battery and put it in the sun again. Sure enough, all was good!

Renogy Solar Panel
All working again!

A simple, easy fix.

Conclusion

There are some basic tools which, if you know how to use them, can help you diagnose and fix some of the most common issues you're likely to have in and around your RV.

Although diagnosing and fixing these two issues was straightforward, using my multimeter allowed me to confirm the diagnosis and my eventual fix, quickly and reliably.

Obviously there are many other things that can go wrong with solar panels, but I hope this blog post gives you a few clues for where to look and how to fix some of the most basic issues you might run into.

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