5 COMMON MISTAKES THAT PEOPLE MAKE
WHEN SETTING UP AN OFF-GRID SOLAR SYSTEM
Solar power is a very simple technology. There’s no moving parts. No combustion. No hazardous waste. However, that does not mean that it’s idiot proof.
Where there be humans, there be fools.
You can actually blame the simplicity of solar for misleading people into believing that it’s simpler than it is. They don’t know what they don’t know. Luckily, I know, and you’re here, so I’m going to share it with you. Top Secret. Don’t tell nobody.
Common Mistake Number 1:
Wiring Solar Panels in Parallel (12 Volts)
When I set up my first solar rig I wanted to avoid as much of the math as I could. I didn’t want to bother with any equations. I wanted to keep it “easy”.
So, I, like most people starting out, wired up my entire system in 12 volts. The panels, charge controller, batteries, and inverter were all 12 volts. It was simple, it was easy, and it barely made a pot of coffee before the inverter alarm would start screaming at me.
I spent $1,200 on that system, and I made it the worst it could possibly be. Imagine buying a corvette, but then having a mechanic alter the engine to make it run on only 2 cylinders instead of 8. That’s wiring your panels at 12 volts.
All I needed to do was throw the PWM charge controller into a lake, and then spend a few more $20 bills on an MPPT. That would have given me access to more of the cylinders (voltage) already in my engine (solar panel array).
Even if you’re only planning on running 2 solar panels, and you’re thinking that the cost of an MPPT controller isn’t worth it for such a small array, you are horribly mistaken. Those 2 panels wired in series (24 volts) are going to create much more power than wiring them in parallel (12 volts).
PWM controllers require that the panels and batteries be wired at the same voltage, but an MPPT allows for the panels to be at a much higher voltage than the batteries and inverter.
Most importantly you’ll get more power in the early morning and later evening. The same amount of sunlight (amps) will be hitting the panels, but the available power (watts) will be higher when the panel voltage is higher.
For an off-grid solar system early morning and late evening are crucial for power generation. You need to make sure that your batteries are completely topped off before the sun goes down, and in the morning when your batteries are low from running the fans and fridge all night, you’re going to want to start that coffee pot.
Speaking of coffee pots…
Common Mistake Number 2:
The 20 Degree Fallacy
Somewhere along the modern timeline someone came up with the “genius” idea to angle solar panels at 20 degrees. “It’s the sweet spot!”, they proclaimed. “It’s right in-between the 40 degree angle for winter, and the 10 degree angle for summer!”
Please, don’t do this. This is chasing the wrong goal. These angles are derived from the idea that achieving maximum power at peak hours (11am-1pm) is the end all be all to setting up a good solar system.
No. It’s the end all be all to selling power back to the grid. If your goal is to lower your electricity bill then by all means set those panels up at 20 degrees. But, if you’re completely OFF-grid, and you want to run that coffee pot in the morning then do not angle your panels at all in the summertime. Lay them flat. Angling panels in summer guarantees that you will NOT get any sunlight on them until AFTER 9 o’clock in the morning.
Laying the panels flat, however, will give you sunlight (amperage) at 7am, and full batteries by 8:30. It’s kind of a no brainer.
You will get more power than what you need at “high noon” in the summertime. Doesn’t matter the angle. There’s no need to make that the goal for an off-grid setup. What are you going to do with all that power when there’s no grid to sell it to?
It needs to be known that Off-Grid Solar and Grid-Tie Solar are 2 completely different schools of thought with different goals. A jazz guitarist and a heavy metal guitarist are both playing guitars, but they are not playing the same style of music. If the jazz guitarist tried to play heavy metal on stage with the jazz band it would be a disaster.
Everybody I know who is off-grid, and has their panels angled at that 20 degree Grid-Tie Sweet Spot has to run their generator in the morning.
I don’t own a generator, but I wake up every day to freshly brewed Colombian Supremo, frozen ice cream, and plenty of power to crank up some Pantera.
Common Mistake Number 3:
Charge Controller Too Close to Panels
Most off-grid setups avoid placing solar panels on roof tops. Unless the roof is flat, a rooftop array brings an army of problems, and most off-grid abodes are on rural land with plenty of available space for an external array.
What this means is that the panels are anywhere from 20 ft to 200 ft away from the house and batteries. This is completely fine, as long as the charge controller is mounted to the house, and not the solar panel rack.
Solar is DC power. Direct Current. DC is more efficient than AC (alternating current), but it suffers from power loss over distance. That’s why all of the power grids are AC. This allows a power plant to generate electricity, and then send that electricity 100 miles away to people’s homes with zero power loss.
DC can’t do this, and that short distance from your solar panel array to your barndo will suffer a voltage drop. This is why the charge controller can NOT be placed on the array.
The power line from the solar panels to the charge controller is the highest voltage line. It can weather the most voltage drop. The MPPT controller is designed to take in that high voltage and convert it down to a smooth 12 or 24 volts to send to the batteries.
If the panels are wired at 48 volts, and they lose 2 volts over that 20 ft distance, no problem. Your charge controller will still have an easy time converting those 46 volts to 12 or 24. But, if the charge controller is sending 12 volts across 20 ft you are only getting 10 volts to the batteries and inverter.
Obviously, these are not exact numbers. I’m just using them for reference. But, the fact of the matter is that the line from the panels to the charge controller is the highest voltage line so therefore must be the longest line because it has the extra voltage to spare.
Common Mistake Number 4:
Running the Inverter on 12 Volts
The inverter is the most power hungry device within the solar system. It converts DC power to AC, and allows you to power items like the coffee pot, microwave, and vacuum cleaner. All of your high power appliances will be run through the inverter.
So, obviously, it needs a lot of power.
If there is one thing that I hate more than PWM charge controllers it’s 2000 Watt 12 Volt Inverters. These things should not exist! Imagine taking that same corvette we bought earlier, but now asking the mechanic to replace the gas tank with a 2 liter bottle. Sure, we’re running on all 8 cylinders and we’ve got lots of power, but only for a few minutes!
The charge controller is like that big orange Gatorade jug on the side of the football field. The top of the jug has a huge opening and a lot of Gatorade can be poured in at once. Your solar panel voltage is the diameter of that opening, and the sunlight is the Gatorade.
But, that little spigot on the bottom that is used to fill the cups is your battery voltage. Which is also your inverter voltage. It doesn’t matter how much Gatorade is pouring into the top of the jug. Only what can get through that spigot is what is going to the inverter.
If the inverter needs more power than what the charge controller can provide then it will pull the power it needs from the batteries. This can drain the batteries very quickly.
Raising the battery / inverter voltage makes that spigot on the bottom of the Gatorade jug bigger, and allows the charge controller to send more power from the panels to the inverter.
The inverter will also run more efficiently on 24 volts which makes it require less power from the batteries when you are microwaving hot pockets at night.
It’s win, win, win.
The reason that most people don’t do this is because they are misled by the Amp Hours labeling that comes along with battery marketing. We’re told that 2 batteries wired in parallel (12 volts) will give us double the amp hours of 2 batteries wired in series (24 volts).
Nobody wants to spend $300 on solar batteries and then only get “half the capacity”, so they wire them up in parallel (12 volts).
All they’re really doing is shutting off cylinders in their new corvette’s engine, and tossing out the gas tank.
The other side of this issue is…
Common Mistake Number 5:
Running Everything On the Inverter
Remember the only reason why homes on the grid are powered by AC is because there is no power loss over distance. AC allows one power plant to power millions of homes.
Your solar panels are only powering 1 home, and it’s 20 ft away. You don’t need to run every appliance, every light, and every outlet at 110 volts (AC). This is a waste of power. Even appliances with the Energy Star sticker are not designed to be “low power”. Just less power than the 1970’s model.
Wiring your lights, charging outlets, and smaller appliances like the refrigerator, phone charger, and fans on 12 volts will make your off-grid home super efficient. Keep your items that require a 110 plug (that standard house plug) near the inverter. Everything else should run on a 12 volt system.
This is where 12 Volt shines: Powering low power systems. This is why a Step Down Converter is essential to every off-grid solar system.
The Step Down Converter converts the 24 volts coming from the batteries wired in series, and steps it back down to 12 volts. This way you can power low power items with the least amount of power needed.
It also doubles your amp hours giving you “full capacity” from your $300 solar batteries.
Again with the win, win, win.
A 30 Amp / 350 Watt Step Down Converter is $20.
Again with the no brainer.
Setting up your system as a hybrid system is the best option for an off-grid home. Run your inverter and batteries at 24 volts, your panels at 48 volts or higher, and then step it all down to 12 volts to charge your phone. There are no sweet spots. Each part of the system has different needs to run correctly. Trying to mash them up into one gives you the rumbly bumbly of the generator in the morning.
Let’s Recap!
Wire Panels in Series / Avoid PWM Controllers
Lay Panels Flat in Summer / 40 Degrees for Winter
Don’t Take Advice from Grid-Tie Solar Engineers
Keep the Charge Controller Closer to the Batteries Than the Panels
24 Volt Inverter, 24 Volt Inverter, 24 Volt Inverter
But, Don’t Run the Entire House on the Inverter
Step Down Converter is a Must
There is No Sweet Spot!
Here’s a link to my recommended appliances, including 12 volt refrigerators.
LINK
To order a pre-wired solar system board click here:
LINK
To build your own solar system board click here:
LINK
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