Solar charge controllers, also known as solar regulators, convert the raw power delivered from a PV solar panel into a usable charge for the battery. Charge controllers sit between the panels and the batteries, acting as a converter for the mismatched voltages of the two components.
The voltage in a PV array varies with temperature, light intensity, and other factors. Batteries expect a specific voltage and cannot handle fluctuations in power on their own. To regulate these changes in voltage, you need to install a solar charge controller between your PV array and solar battery bank.
There is more than one type of solar charge controller—which one is suitable for your array?
The Two Types of Solar Charge Controllers
There are two main types of solar charge controllers: Maximum Power Point Tracking (MPPT) and Pulse Width Modulation (PWM). The two perform similar functions, but MPPT is typically the better choice for residential solar systems. Let’s take a look at the differences.
MPPT (Maximum Power Point Tracking) Solar Charge Controllers
MPPT (Maximum Power Point Tracking) charge controllers employ newer, more advanced technology than PWM controllers. MPPT controllers allow the solar array to perform at its “maximum power point,” which is the ideal current and voltage. Other charge controllers will waste excess energy generated by the solar panels, while MPPT controllers can convert this into more power for the batteries.
MPPT technology has been around for a few decades, but it has only recently become affordable enough for the average homeowner. Most advanced residential solar power systems utilize MPPT charge controllers. Some estimates claim that using an MPPT controller can increase the efficiency of a solar system by around 30%. MPPTs achieve higher efficiency by boosting the amperage provided to the battery by converting excess voltage.
MPPT controllers are always the better choice for residential solar setups. Any system that uses multiple panels will benefit significantly from the higher efficiency of an MPPT controller. This is true for all systems where the PV array operates at a higher voltage than the battery bank. Other types of controllers would waste this excess power.
MPPT charge controllers will generally cost more than PWM controllers. However, the higher initial purchase cost provides savings over time due to the controller’s ability to harvest more power from the same amount of solar panels.
When batteries are nearly depleted, they operate at a lower voltage and usually receive a charge at a lower rate. An MPPT is helpful in this situation, as it can convert the extra voltage into more amps for the depleted battery.
If crafting your own solar system piece by piece seems overwhelming, there are also all-in-one bundles that simplify the installation process. For example, EcoFlow Power Kits have everything you need to set up a high-quality off-grid solar system. It includes the battery, cables, distribution panels, and a power hub with a built-in MPPT solar charge controller. Just purchase your required solar panels, and you’re ready to start harvesting renewable electricity from the sun!
Let’s recap the pros and cons of MPPT charge controllers.
- Efficiency — MPPT Controllers can convert excess voltage into more usable current.
- Ideal for large systems that have varying voltages, such as a PV array with a higher voltage than the battery bank
- Performs well in both warm and cold climates
- Useful for both small and large applications, including RVs, cabins, and traditional homes
- More expensive than PWM controllers
PWM (Pulse Width Modulation) Solar Charge Controllers
Pulse width modulation controllers are an older, cheaper technology. They are less efficient than MPPT charge controllers. If all other factors are the same, a solar array will take longer to charge a battery bank when running through a PWM controller.
PWM controllers perform a similar function to MPPT controllers, as they still regulate the energy that flows to your battery bank. However, they accomplish this action in a different manner.
The “pulse width modulation” refers to how a PWM controller slowly reduces the current while charging the batteries. When the batteries reach maximum charge, PWM controllers will trickle charge the batteries — this means that they will continuously provide a small amount of power to keep the batteries topped up.
To use a PWM controller, your batteries and solar panels must operate on the same voltage. Large residential solar systems will not be well-served by this type of controller.
PWM controllers can only use the power you generate up to the voltage of your battery bank, which is usually around 12V. The extra power goes to waste if the solar panels provide more energy. The loss of solar energy from using a PWM is in contrast to the ability of MPPT controllers to step down the voltage and boost the current.
PWM controllers are best for warmer climates where the MPPT “boost” does not benefit a system as much. And since the controllers are cheaper, PWM may be suitable for small systems where investing in an MPPT controller isn’t cost-effective.
Let’s recap the pros and cons of PWM charge controllers.
- Great for warm, sunny weather
- Works well for small, single-panel systems
- Not designed for complex solar arrays that contain varying voltages
- Inefficient—excess power produced by your solar panels goes to waste
How to Determine Which Solar Charge Controller Is Right For You
For modern residential or large recreational solar systems, the only real choice is between MPPT and PWM charge controllers. You may see some mention of shunt or series controllers, but these are no longer used for residential applications.
MPPT charge controllers are always the right choice for a DIY home solar system. Their superiority extends to RVs, cabins, and other off-grid applications. Unless you are only using one or two panels — such as on a camping trip — the additional benefits of an MPPT charge controller are worth the slightly-higher investment.
In some cases, you won’t need to purchase a separate solar charge controller. EcoFlow Power Kits are a popular way to get started with solar quickly, and the MPPT charge controller comes built-in! It also makes for a safer solar system for inexperienced homeowners, as there is no chance of improper installation, compatibility issues, or choosing the wrong controller.
Now that you know the differences between the two types of charge controllers, you can go out and purchase your own. The only thing left to determine is what the amp rating of your controller needs to be. You can make this decision easy by buying a controller with a higher power rating than what your solar array will provide.
If creating your own DIY solar power system isn’t your style, look at all-in-one options. EcoFlow Solar Generators make solar power accessible for anyone — all you need is the generator and a solar panel to get started on your journey towards renewable energy independence.