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How Does A Solar Charge Controller Work? (PWM & MPPT)

Written by Eddie B. Robinson / Checked by Justin Tucker


how does a solar charge controller work

As people are becoming more cautious about climate change, many have begun to use environmentally-friendly products to limit their carbon footprint. If you have a solar panel at home, you need to understand a key component of this technology, the solar charge controller.

Why? Because knowing how does a solar charge controller work will let you choose a good fit for your solar panel array. Choosing the wrong one could render your solar panels useless.

How Do Charge Controllers Work


For you to understand this concept, you need to know first how electricity flows. Like diffusion, where particles move from a highly concentrated region to a lower concentrated one, electricity flows from a high voltage to a low voltage region.

So, for example, solar panels can produce energy in the daytime because of the presence of the sun, giving them a higher voltage than that of your battery. So whenever the solar panels produce excess electricity, it is sent directly to your battery.

But at night, there is no sun, so your battery now has a higher voltage than that of your solar panel, which means electricity can flow back to your solar panel. So what does your solar charge controller do about this?

Well, it manages and keeps the electricity in its rightful place, in your battery. Because solar charge controllers only allow a flow of electricity in one direction, it acts as a valve at night, so no discharge happens to your battery.

Also, charge controllers prevent your battery from over-discharging. When the voltage falls below a certain boundary in your battery, they will automatically disconnect the battery bank’s non-critical loads. We call this a low voltage disconnect or LVD.

And if you are worried about your battery overcharging, don’t, because your solar charge controller will only direct a small amount of energy to it whenever your battery is full.

PWM And MPPT – The Two Main Types Of Charge Controllers

So there are two types of solar charge controllers out there, the PWM or pulse width modulation and the MPPT or maximum power point tracking.

Regardless of what battery charge controllers you use, it will all boil down to the number of amps they can handle and give to your battery. So it is important to match the maximum power current (IMP) of your solar panel to the maximum amount of amperage your charge controller can handle.

Why? Because you can severely damage your charge controller if its maximum amperage is lower than that of your solar panels.

PWM solar charge controllers

A PWM solar charge controller is the simplest type because it only establishes a direct connection between your battery bank and solar panels. It is also why it is the cheapest.

You can only use PWM if its maximum allowance of voltage is the same as the maximum voltage of your solar panels.

MPPT Solar charge controllers

MPPTs, on the other hand, are more complex than PWMs, because they measure the maximum power (VPM) voltage of your solar panels and down-convert the solar panel voltage before it flows to your battery.

This means that you can harvest at a higher voltage than your battery without getting the latter overwhelmed. Just make sure the open-circuit voltage (VOC) of your solar panels is permitted by your charge controllers.

What Type Should You Choose

I would say that it depends on how you are using your system. If you are using a small system for your RV or an AGM battery, PWM would be best since it is cheaper and there is no necessity for efficiency.

But if you have a large system like that of a house or have a solar array that produces more voltage than your battery can handle, then your safest option would be an MPPT.


Knowing how does a solar charge controller work is important as it will guide you on what types you should buy for solar panel arrays. Different solar panel systems will require a specific type of solar charge controller to function properly. Plus, they can have different specifications, too.

Solar panels may be a great investment, but they are not cheap, and if you choose the wrong solar control charger, you might damage your solar panel array. So apply what you have learned from this article when you look for a solar charge controller.

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