As many of you know, we’ve been off grid for roughly 46 years now. Seems like yesterday that we were jumping up and down when we put 2 amps of solar charging back into our car battery which was our “system”.
And if you read any of our books, you would know I started my career as an industrial electronics technician. My last electronics job was designing and building test equipment for circuit boards used in robotics. Yes, even back in the stone age, there were rudimentary robotics that would mechanize certain elements in manufacturing. They were called pick and place machines.
Solar Array for Energy Independence
And all of that electronic stuff used standard alternating current we use in our houses today along with low voltage direct current gadgets. Hopefully, my dear readers clueless about electricity will still find this of interest. Anybody with some electrical knowledge will find this an invaluable education.
Electronics and Electricity
I understood electronics and electricity so it wasn’t hard to make the leap to designing and wiring up my solar electric systems for our home. And as mentioned, the first system was ridiculously small so we were always power starved even when we added some additional solar panels to our Maine homestead.
When we moved to the wilderness of northern Saskatchewan, our system became much larger. For 17 years we lived out in the bush with a trouble free solar electrical system.
Then we moved to our current location in Nova Scotia and built an even bigger solar array and system. Now we are talking some serious power. Remember I was happy with 2 amps at the very start? Now our system can push 100 amps into the batteries. That’s a big jump!
And along with that jump in power, electronic components and wire size get bigger and connections become more critical.
Up until last year, we had 7 years of trouble free service. I have a remote meter here in my office. It allows me to see many metrics including how many amps are going in and out of the battery as well as tracking my amp hours used and battery state of charge. Consider the meter my fuel gauge much like in a car. How much gas do I have left in the tank? How much energy do I still have left in my battery?
Nova Scotia, We Have a Problem
A while back, I noticed my meter fluctuating wildly when solar power was coming in on a sunny day. My meter might read 40 amps then jump to 600 amps going in. Well since my system can only deliver 100 amps, something was surely amiss here. This was clue 1 that something was wrong.
I changed meter cables, checked wiring etc and everything looked good. Since everything electrically seemed to be working, I chalked it up to a bad meter or perhaps bad shunt sending unit. Since everything is networked together, the bad meter readings were distorting what my charge controller was doing. In other words, my charge controller didn’t know what to make of these numbers and somewhat shut itself off since it thought the batteries were full when they really were not.
Meter Shunt
So I just disconnected my meter and made a judgment call from experience what state of charge my batteries were. I ordered a replacement meter as the first obvious thing to try.
A week later, I noticed the smell of something getting very hot. This was clue number 2 something was really wrong. I looked at the wiring in my power box but couldn’t see anything wrong. I didn’t take the cover off the solar charger since there’s only 5 connections and surely everything is fine in there.
So I went downstairs and noticed a big red light on my solar charge controller. The display showed a fault code. In essence, these components are pretty smart and know when there’s a problem so they alert you to it.
I couldn’t get rid of the code. Clue number 3! Then I took a closer look at some of my wires in the power box which were obviously discolored with melted insulation. I took the cover off my solar charger and by golly, the battery plus wire was discolored and obviously had cooked as well. I had 2 locations essentially in the same line that had seriously over heated.
This was a real head scratcher since one would think extremely high current went through those heavy wires to cause insulation discoloration from heat. More than they could possibly handle. And yet, those wires were sized to easily handle 100A current and I had a circuit breaker in line too which would have tripped if I exceeded a current limit.
Toasted Wires
How can wires be getting melting hot in 2 different locations? I was able to reset the solar charge controller fault enough that my system started charging the batteries. But even at a modest 30 amps going in, the buss bar where some of my connections were along with the input to the charge controller were getting extremely hot. That buss bar was hot enough to singe a finger tip. (Ask me how I know)
Talk about being under pressure. We couldn’t recharge our system until I figured out this mystery. My electronics training kicked in and although I thought I had the answer, I was a bit in disbelief that after 7 years of flawless energy production, on the same day, I had 2 bad connections appear in 2 different locations. That really seemed to be a stretch and yet you guys and gals familiar with high power systems and connections understand how devastating a bad connection can be.
I shut the system down, took the wires out of both locations and sure enough, it was obvious the wires were blackened with insulation discolored or burnt to a crisp. And even though the connections seemed tight, obviously they were not tight enough.
Simple Solar Power Math
Let me explain something with some simple math. You don’t need to understand it but viewing the numbers will demonstrate the concept. I took my courses in electronics over 50 years ago and I still remember my power equations in my head. Here’s the one we will use.
P = I²R Where P is power in watts, I is current in amps and R is resistance in ohms.
All you need to know is when we make an electrical connection, we want the least amount of resistance in the connection. That essentially means we have a good, tight connection. Any resistance in our connections means we have a bad connection. Just remember that concept as we work a couple math equations.
The sun is just coming up and my solar panels are putting out 5 amps of current to the batteries. The panels are connected to my charge controller which regulates how much goes to the batteries. All 5 amps are flowing from the solar panels through the various connections on the charge controller directly to my batteries. Let’s assume I have a good connection and for the math, let’s say I have .05 ohms of resistance at my connection. ( I have no idea what the actual resistance is but use that as an example)
Let’s plug the numbers into the equation. P= 5² X .05 therefore, I have 1.25 watts of heat being dissipated in my connection. No big deal.
Sun is now higher in the sky and I’ve gone from 5 amps to maximum energy from the sun of 100 amps. P= 100² X .05 Things are starting to get warm. Our connection is dissipating 500 watts. A typical hair dryer uses roughly 1500 watts. So our “good” connection is still generating considerable heat.
Now let’s introduce a “bad” connection. Maybe our connection wasn’t tight. Maybe we have some corrosion in the connection. Instead of .05 ohms of resistance, we have .3 ohms. That’s still a teeny tiny amount of resistance but as you will see, it makes a huge difference in power.
Let’s go back to the previous two examples and run the numbers. My solar panel is putting out 5 amps. P= 5² X .3 therefore, I have 7.5 watts of heat being dissipated in my connection. Still no big deal.
Sun is now higher in the sky and I’ve gone from 5 amps to maximum energy from the sun of 100 amps. P= 100² X .3 Things are HOT!!! Our connection is dissipating 3000 watts. That’s double what your hair dryer would be using. Instead of blow drying your hair to dry it, you are going fast track with your hair on fire.
Solar Electric System Wiring Lesson
This is a theoretical example intending to show how a small change in resistance due to a poor connection coupled with more current coming from the solar panels can create havoc with wires.
Here’s the lessons for the day. We want the best electrical connections possible. Clean tight, low resistance connections for our wiring.
When we go to install a solar electric system, we generally have new components and shiny wires. Assuming we do a good job with wiring, our connections should be good and tight.
Unfortunately, there can be complicating factors. Some components use terminal boards soldered direct to a circuit board. Mine was like that. It’s a judgment on how much torque to screw the wire into the terminal. Too much and I snap the connector and ruin a $1000 or more gizmo.
The other complicating factor is large wires made up of individual strands. Over time, those strands can settle in and compact down which means just a slightly less tight connection. Over time, with current and heat, now the joint starts to corrode. Which makes things even worse. At this point, things feed on them selves until you ask “What’s that burning smell?”.
Terminal Strip and Wires
I never had a system capable of putting out this much current. In hindsight, after some period of time transpired, I should have opened everything up and re-tweaked all of my connections to make sure they were good and tight. I suggest that be mandatory for everybody who is pumping out serious current. Go back in maybe 6 months time and just make sure all connections are still tight. It took 7 years before my connections gave me problems which could have been avoided had I gone back and double checked all my connections, especially when those connections are a terminal board which has a limitation on how much you can really tighten without damaging the component.
Until next time, keep the dream alive. We wish you a good day!
Ron and Johanna
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