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What is a Solar Charge Controller?
Also, we have interactive solar wiring diagrams that are
Finally, for this blog post you’re reading right now, we have a calculator that will help you choose a charge controller. I HIGHLY recommend reading this post to truly learn how to use the calculator, but if the calculator is all you’re looking for, you can download that HERE.
How does the Charge Controller Work?
Solar panels typically put out a voltage that is too high for batteries to use. If you have your solar panels wired in series
MPPT vs PWM CHARGE CONTROLLERS
There are two main types of charge controllers. They are MPPT and PWM. This blog post is a crash course in solar design and getting into the specifics of the differences is out of the scope of this blog post. Here’s what you need to know regarding MPPT vs PWM charge controllers MPPT is the newer, more efficient technology. From here on out, any time I talk about charge controllers, I will only be talking about MPPT charge controllers as I want to guide you to build a high-end, expandable solar setup.
HOW TO MATCH SOLAR PANELS TO A CHARGE CONTROLLER
One of my favorite series of charge controllers is the Victron BlueSolar MPPT Charge Controller. If you’ll notice, there are MANY different sizes of charge controllers:
- Victron SmartSolar MPPT 75 | 10
- Victron SmartSolar MPPT 75 | 15
- Victron SmartSolar MPPT 100 | 15
- Victron SmartSolar MPPT 100 | 20
- Victron SmartSolar MPPT 100 | 30
- Victron SmartSolar MPPT 100 | 50
- Victron SmartSolar MPPT 150 | 35
- Victron SmartSolar MPPT 150 | 45
- Victron SmartSolar MPPT 150 | 60
- Victron SmartSolar MPPT 150 | 70
- Victron SmartSolar MPPT 150 | 85
- Victron SmartSolar MPPT 150 | 100
- Victron SmartSolar MPPT 250 | 85
- Victron SmartSolar MPPT 250 | 100
WHAT DO THOSE NUMBERS MEAN?!?
Let’s say, for example, you have 4 x
EACH 100w solar panel has an Open-Circuit Voltage (Voc) of 21.6 volts. and an Optimum Operating Current of 6.72 Amps. Those are the only two numbers we are concerned about for now. I generally recommend just wiring all of your solar panels in series for simplicity and efficiency sake. Which means: Those 4 x 100 watt solar panels get wired together like this:
Since they are wired in series, the voltages get ADDED together for a total of 86.4 volts. (Open-Circuit Voltage (Voc) of 21.6 x 4 panels) The amps on the “upstream” side of the 100w solar panels
So, the 86.4 volts is under the safe threshold of the 100 max volts of the Victron SmartSolar MPPT 100 | 30 solar controller.
100 is the first number. What about the 2nd number, 30?
The 30 in the Victron SmartSolar MPPT 100 | 30 is the MAX resulting amps AFTER the solar controller has worked
- We have 4×100 watts of solar panels totaling 400 watts of solar.
- Assume batteries are 12.6v
- Amps = Watts / Volts
This means, that at 400 watts and 12.6v we can expect up to 31.74 amps coming out of the solar controller.
Now, we are talking about that Victron SmartSolar MPPT 100 | 30, we have to compare that 2nd number, 30.
31.74 amps is a bit over the 30 amp threshold. BUT…
Solar panels rarely put out their full wattage. AND…
In the Victron SmartSolar MPPT 100 | 30 manual, they say their controller is good for solar arrays up to 440 watts:
AND… If you happen to go ‘over’ on your Amperage, it’s not that big of a deal in terms of damage. It’ll just be lost power that the controller won’t convert.
So, basically, the Victron SmartSolar MPPT 100 | 30 is pretty perfect for those 4 x 100 solar panels.
But what if you like playing it safe? What if you want some wiggle room? Great! Size up to the Victron SmartSolar MPPT 100 | 50. Sure, it’s a little more money, but if it’s worth your
Now, Why would you want wiggle room or safety margin? Let’s talk about temperature
Solar Controller vs Temperature
DID YOU KNOW… As temperatures drop, solar panels actually put out MORE power.
Totally honest though, the math gets messy, SO I made a calculator that you can input all of the values for your setup so YOU can see how temperature affects your solar panel setup AS WELL AS will give you a recommendation on what solar controller you need taking solar panel temperature into account.
Access that calculator (and it’s instructions) for free, here
Now that you’ve gone through the Charge Controller Wizard, you’ve gotten a very helpful piece of information:
Based on the inputs, you now have a recommended charge controller size that takes temperature into account.
Sure, it says “Solar Controller 100 | 40” which is formatted like the Victron charge controllers, but you can, ultimately use any charge controller brand you like. The premise is mostly the same.
Now… a Victron SmartSolar MPPT 100|40 doesn’t exist. All you have to do, is simply round up to the next nearest available size, which would be the Victron SmartSolar MPPT 100|50.
*This calculator will give you some wiggle room and a buffer for the panels you have input. If you feel you want to round down a size, ALWAYS listen to the minimum specs that the manufacturer has made.*
Confused? Don’t want to do math?
No problem. I’ve got you…
Here is a list of solar panel combinations with my recommended Victron solar controller size. I’ve picked these combinations assuming you’ll never be somewhere with a daytime high of colder than -10 degrees Fahrenheit.
- 100 Watt Solar Panel Options:
- 100 watts: Victron SmartSolar MPPT 75 | 10
- 200 watts: Victron SmartSolar MPPT 100 | 20
- 300 watts: Victron SmartSolar MPPT 100 | 30
- 400 watts: Victron SmartSolar MPPT 100 | 50
- 175 Watt Solar Panel Options:
- 175 watts: Victron SmartSolar MPPT 100 | 20
- 350 watts: Victron SmartSolar MPPT 100 | 50
- 525 watts: Victron SmartSolar MPPT 100 | 50
- 700 watts: Victron SmartSolar MPPT 150 | 70
- 875 watts: Victron SmartSolar MPPT 150 | 100
Now that you know what kind of charge controller is compatible with your solar panels, it’s time to learn how to choose an inverter for your DIY Camper setup. Check that out here:
Everything that you are learning here is put to use in our FREE Interactive Solar Wiring Diagrams. If you haven’t yet, check them out as they are a complete solution for a camper van electrical system. Check them out here: https://www.explorist.life/solarwiringdiagrams/
Remember, this is just one part of a full camper van electrical educational series. To see all of the individual guides, click here: https://www.explorist.life/diy-campervan-solar
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