Are you considering installing solar panels on your motorhome’s rooftop to operate your RV appliances with clean, free, and efficient energy? You might also be confused about which PWM vs MPPT charge controller for RV you should pick.
Like many novice RV owners hoping to improve their RVing adventures, I know how challenging it is to set up a solar system in your vehicle. Understanding what an MPPT or PWM solar charge controller does will help you create the most efficient energy system for your motorhome.
In general, MPPT charge controllers are more expensive than PWM ones, though they’re also more efficient.
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What is a Charge Controller
A solar energy system for RVs and marine vessels has four essential components. These include solar panels, power inverter, charge controller, and deep cycle batteries.
The solar panels gather solar energy and convert this into DC electricity, which the deep cycle batteries store. Some RV appliances require AC power to run, requiring an inverter to transform battery-stored DC electricity into AC electricity.
Where does the charge controller come into the picture?
You can think of the charge controller as a traffic officer, directing and regulating the flow of electricity between the solar panels and the deep cycle batteries. It ensures the battery receives the correct amount of electricity to maintain its charge while also preventing overcharging.
At night when there is no sun to power the solar energy system, the charge controller also limits the backflow of current from the batteries to the solar panels. When you wake up the following morning, your battery will still have plenty of juice to run the different appliances in your RV.
Currently, there are two charge controller types: MPPT vs PWM charge controllers.
What is a PWM Charge Controller
Pulse Width Modulation or PWM is an old technology that remains relevant today because of its durability, proven performance, and affordability.
Without getting technical, a PWM charge controller is like an ordinary electric switch that controls the flow of electricity between the batteries and the solar panels.
If your batteries are near-empty, the charge controller allows the influx of energy at a rapid rate. As the battery reaches a certain charge level, the controller reduces the electricity’s flow and the amount going to the battery. It keeps the battery at its peak charge without overcharging.
What is an MPPT Charge Controller
A Maximum Power Point Tracking or MPPT solar charge controller works like a PWM controller, except that it tracks the solar panels’ output current and voltage in real-time. It also constantly monitors the solar energy system’s maximum power while regulating solar panels’ output voltage.
This unique attribute allows MPPT controllers to ensure battery charging using only maximum solar power.
You can look at an MPPT controller as a multistage battery charger. It has the PWM’s progressive charging characteristics. Additionally, an MPPT controller also allows for automatic switching of the charging method, depending on solar panel conditions and output.
PWM vs MPPT Charge Controller for RV: What Makes Them Different in Charging Batteries
Either PWM or MPPT charge controllers can recharge solar batteries safely. However, there are several substantial differences.
Both controllers charge batteries in three stages: bulk, absorb, and float. Unfortunately, PWM controllers bulk-charge batteries at a constant voltage value.
On the other hand, an MPPT controller automatically adjusts the solar panels’ output voltage to recharge the deep cycle batteries. As a result, the MPPT controller ensures more efficient solar energy utilization.
That is why the energy conversion rate of an MPPT charge controller can be 30 percent higher than a PWM controller. For example, high-end PWM charge controllers have an energy conversion rating of 75 to 80 percent. By comparison, an MPPT controller can provide up to 99% solar conversion to electricity.
A PWM controller typically waits for the system voltage to stabilize and fall naturally before initiating the absorb charging state. An MPPT charge controller does not wait for such an occurrence. It automatically decreases the charging current and ceases the constant voltage charging.
MPPT controllers also have an additional charging stage: boost or balance charge. It constantly monitors the solar array’s power output, using only the maximum power to charge the batteries.
Summing these solar charge controllers’ charging capabilities, you can say that the MPPT’s four-stage charging mechanism is better, safer, and healthier for your RV’s deep cycle batteries than a PWM’s three-stage design.
PWM and MPPT Charge Controller Applications
While MPPT controllers have the edge in battery charging efficiency, it would be unwise to count PWM out of the picture. This technology remains a favorite for small-scale solar system applications because it is more cost-efficient and is straightforward to deploy.
A PWM charge controller has a few electronic components; after all, it is more like a switch. On the other hand, an MPPT charge controller has a complex design, often involving more advanced electronics. If you are a greenhorn in electrical systems, I suggest sticking with PWM controllers.
In general, a PWM charge controller is ideal for small-scale solar projects, generating less than 2,000 watts. The controller can accommodate up to 60 amperes and run on 12 and 24-volt systems.
PWM charge controllers are suitable for RVs, marine vessels, motorhomes, campers, buses, and trucks.
If you are looking to expand your solar energy applications, there is no better charge controller to get than an MPPT. This device is perfect for solar power systems that generate more than 2,000 watts. It can handle up to 100 amperes and operate on 36 and 48 volt systems.
However, it is not uncommon to see some people using MPPT controllers with 12 and 24-volt batteries. While it is okay, I think it is a waste of the charge controller’s potential.
Which is a Better Charge Controller, MPPT or PWM
We now come to the most obvious question you may have. Which should you pick for your RV’s solar energy system: MPPT or PWM charge controller?
Honestly, it all boils down to your budget and solar energy requirements. If you need to run power-hungry RV appliances and devices, an MPPT charge controller is a better choice.
While it is more expensive than a PWM controller, you can enjoy savings from its robust features and exceptional solar-to-electricity energy conversion efficiency.
However, if you are working on a tight budget and will run only a few energy-saving devices and appliances in your motorhome, a PWM controller will suffice. It is also more effortless to maintain, saving you money from expensive repair and maintenance.
Based on their function alone, an MPPT charge controller will always come out on top. It is essential to understand that the solar array’s output voltage should always be higher than the battery’s input voltage.
Unfortunately, the output voltage is not constant. It fluctuates depending on the time of day, light intensity, dampness, and ambient temperature.
PWM controllers do not account for these environmental factors, operating only on the assumption that the solar arrays produce a constant voltage. That is why they tend to waste so much energy.
MPPT controllers solve this issue by tracking the maximum energy points in the solar array. It automatically adjusts the flow and frequency of energy movement between the solar panels and the battery, ensuring no solar energy goes to waste.
Deciding on PWM vs MPPT charge controller for RV is a matter of personal preferences, budgetary constraints, and technical know-how. If you have a power-hungry RV, do not mind paying more, and know advanced electronics, an MPPT charge controller is an excellent choice.
If you are like most of us who prefer to keep things low-key, a PWM charge controller can be as valuable as its more modern counterpart.