MPPT vs PWM : Which Charge Controller is Better?

In this post, I’m going to put MPPT and PWM Charge Controller to the comparison.

So if you’re looking for a DEEP comparison of these two kinds of charge controllers/regulators, you’ve come to the right place.

Because in today’s post I’m going to compare MPPT vs. PWM in terms of:

• Working Principle
• Operation
• Performance
• Pricing and value
• Unique features
• Expert Recommendation
• And lots more

What a Solar Charge Controller do?

a Solar Charge Controller (aka solar panel voltage regulator) is a kind of controller that regulates the charge and discharge process in the solar power system. the main role of the charge controller is to control the charge current flowing from the PV panels to the battery, keep the current flowing not too large to prevent the battery pack from overcharging.

there are 2 types of charge controllers on the market:

1. MPPT Solar Charge Controller
2. PWM Solar Charge Controller

MPPT vs PWM Comparison Chart

MPPT vs PWM: Principle

MPPT and PWM are both energy control methods used by the charge controller to regulate the current flowing from the solar panel to the battery. PWM Charger is usually asks for a cheap price and has a 75% percent conversion rate, buying an mppt charger is a little pricey, but, the latest MPPT can get a massive conversion rate improvement which up to 99%.

What is MPPT

MPPT Stands for Maximum Power Point Tracking is a technique for tracking and regulate the output energy from the solar panel to the battery.

The MPPT detects the solar panel output voltage and current in real-time and continuously tracks the maximum power (P=U*I), regulates the output voltage correspondingly so that the system can always charge the battery with the maximum power.

What is PWM

PWM is short for Pulse Width Modulation, it’s a technique to modulate the width of pulse under certain rules, thus changing the voltage and frequency of output energy from the solar panel to charge the battery. The PWM controller can be considered as an electric switch between the solar panel and battery packs.

MPPT vs PWM: Charge Difference

Pulse Width Modulation charges the battery with fixed 3 stage Charging (bulk, float and absorb), while the MPPT is Maximum power point tracking and can be thought of as multi Stage charging. The conversion efficiency of MPPT is relatively 30% percent higher than PWM.

PMW 3 Stage Charging:

• Bulk Charge: the bulk generation stage indicates PV system proceeds the most power to the solar battery at the first stage, at that time, the battery voltage at low value, the system will power the battery with high current and voltage. It should state that there is a maintenance point (overcharge protection) and when the voltage at the battery end is higher than this maintenance value during generation, the series charging should be stopped.
• Absorbing Charge: After the first stage of charging, the battery will normally wait for a period of time to allow the voltage to fall spontaneously, and then it reaches the balanced charging stage. This stage is also called fixed voltage charging.
• Float Charge: Float charge is the last stage of 3 stage charging, as known as Trickle charging, A trickle is a small charge current to a battery at a low rate and in a fixed manner. Most rechargeable batteries lose power after being fully charged due to self-discharge. If the charge remains at the same small current as the self-discharge rate, the charge can be maintained.

MPPT Multi-Stage Charging:

MPPT also has a  3 stage charging process, unlike PWM, MPPT has the ability to auto-switch the charge method base on the PV condition. here is how:

• Bulk Charge: at the bulk charge stage, the mppt controller works at Vmpp mode and actively adjusts the output voltage to charge the battery, this enables the system harvests the most power from the PV array. Unlike PWM, at the bulk charge stage, the charging voltage is at a fixed value.
  When the sunlight is strong, the output power of photovoltaic cells increases greatly, and the charging current can soon reach the threshold, abort the MPPT charging and switch to the constant-current charging method.
  When the sunlight becomes weak and hard to hold constant current charge, then switch to the MPPT charging method, and so freely switch until the voltage at the battery side raises to the saturation voltage Ur, the battery reaches the constant voltage charging stage. By combining the MPPT charging method with the constant current charging and automated switching, it is possible to make full use of solar energy to charge the battery quickly.
• Balance Charge / Boost Charge: As the battery is charged to the boost voltage setpoint, the solar controller progressively adjusts the charging current to keep the battery in charging process without excess voltage.
• Absorb Charge: at the absorb charge stage, as the battery voltage increased, the charging current gradually decreases, when the charging current falls to about 0.01C, the constant voltage charging ended.
• Float Charge: The charge voltage (Uf) in the floating charge mode is a little lower than the constant charge. The main purpose of this charging stage is to compensate for voltage drop of the battery. In the process, the battery gets entirely charged.

MPPT Charging Advantages:

1. MPPT Charger Quickly scan the whole I-V curve and track the Panel PowerPoint in seconds.
2. Implemented Innovative maximum power point tracking technology, it has the ability to maximize solar system energy utilization rate, and makes conversion efficiency up to 97%..
3. Increase charging efficiency by at least 20% percent vs PWM charge controller
4. empower the solar energy systems to gaining larger amount of power.
5. With the same load, using the MPPT charging method can lower the power of PV modules and reduce module costs.

the MPPT Charge Curve is shown below:

MPPT vs PWM Solar Charge Controller: Application

PWM Solar Charge Controller is the most widespread, cost-efficient, and readily deployed charge controller solution for small off-grid systems. MPPT Regulators have many more electrical components inside and are constructed more complexly than PWM-type charge controllers.

PWM solar controllers primarily apply in a small 12V or 24V PV system. MPPT controller can also work with 12v, 24v smaller systems but some models can also handle 36v and 48v larger systems when needed. size the right amperage for the controller is simplified with sizing tool.

MPPT Charge controller asks for higher prices than PWM type but has greater applications and in a larger solar project, the mppt controller is the only option to work with.

MPPT vs. PWM: Pros and Cons

MPPT and PWM Charge Controllers perform the same tasks in the solar power system. We generate a list that contains all the advantages and disadvantages of both technologies for your reference.

MPPT Charge Controller Pros

• Maximum Power voltage Tracking Algorism Increase Power Conversion rate up to 99%
• 4 Stage Charging keep the battery in health condition
• Scalable for Large off-grid Power system
• Available for solar systems up to 100 Amps
• Available for solar array voltage up to 200 Volts
• Offer flexibility when system growth required
• Equipped with multiple protection
• Rich modes for load configuration
• Some MPPT controller is able to Charge Lithium (Lifepo4) Battery

MPPT Regulator Cons

• High Prices (usually cost twice of a PWM Charge Controller)
• Larger Size than a PWM regulator

PWM Solar Controller Pros:

• PWM Regulator has mature and proven techniques
• PWM Regulator is a Simple Structure and cost-effective
• Easy deployed in smaller systems
• Less budget for a small tiny homes project
• soma pwm charges can also charge lithium batteries

PWM Solar Charge Controller Cons:

• Low conversion rate
• Input voltage must match battery bank voltage
• Less scalability for system growth
• Inability to handle higher voltages
• Less Load Mode
• Less Protection

MPPT vs PWM Charge Controllers: MPPT Advantages

To charge the battery, the output voltage of the solar panel must be higher than the input voltage of the battery. If the solar panel output voltage is lower than the input voltage, then the charge current will be close to 0 (zero).

Moreover, the output of the solar panel is not a fixed value, the curve changes a lot during the working time, many factors like sunshine intensity, ambient temperature, even dampness can affect solar conversion.

When using a PWM Regulator, as the PWM system lacks flexibility, the setting parameters cannot be changed, which means during the charging process, the output voltage and current remain constant. even the solar input changed, nothing changed to the controller output.

as environmental factors like sunlight level, the surrounding temperature, and humidity are continuously changing. The energy transferred from the solar panels may have dissipated even if the sun is good.

A PWM controller works like a switch and links the solar array directly to the battery when charging. This demands solar array functions in a voltage range that is typically below Vmp.

In a 12V solar system, the battery voltage range is typically 11-15V, but the Vmp voltage of the solar array is typically around 16 or 17V.

Since PWM Controllers don’t always function at PV arrays Vmp, this will cause energy loss, The greater the difference between the battery voltage and the Vmp of the panel array, the more energy wasted.

Thanks to the invention of the MPPT controller, In favor of MPPT algorithm, The controller automatically monitors the high power points of the PV to secure maximal energy derived from the solar array.

In a solar power system, the cost of solar panels and batteries accounts for 80%-90% of the overall budget. and the controller only takes the other 5%-10%. but If you pick the right solar chargers, a 5% budget solar controller can optimize the system to its best performance. Taking an mppt type is highly recommended when you are looking for RV solar solutions. Check the guide here.

Here is an example for you to better recognize the mppt advantages, let’s say you have a 1000W panel system, if you upgrade the PWM controller with an MPPT type, you only need to deploy 700W solar panels to get the same power.

the solar panels’ price is about $2/W on the market, then the whole cost of solar panels can be lowered to $650. In such cases, in larger systems, the savings can be greater, including the cost of upgrading the panels, wiring cables, and more.

Besides, there are many amorphous solar silicon panels on the market. One feature of this panel type is that the open-circuit voltage is high and the discharge is small. This kind of solar panel works better with an MPPT Controller.

MPPT vs. PWM: Circuit Board Differences

Conclusion: Which Charge Controller Is Best For You?

There you have it-an MPPT vs PWM showdown on a feature-by-feature basis. The mppt type is the winner in my eyes, but the PWM charger still has space.

Based on everything you’ve seen, here’s my conclusion:

• MPPT Charge Controller is best for professional owners who seek one controller that accomplishes demanding tasks (Home Power Supply, RV Solar Power, Boat, Hybrid Solar Power, and off-grid power station). Because of its robust features, it can save you money by lowering other expenses and gains much power.
• PWM Charge Regulator is best for small off-grid power applications that don’t need any other features and has much money. If you just need the basic and economical charge controller for a small lighting system that doesn’t try to match the needs of others, the PWM controller is the way to go.

What do you think? Are you going with PWM or MPPT? Did I miss any major features? Let me know in the comments!

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