phocos PWM and MPPT Charge Controllers Instruction Manual
- October 27, 2023
- phocos
Table of Contents
phocos PWM and MPPT Charge Controllers
Differences between PWM & MPPT
PWM: Pulse-Width Modulation
MPPT: Maximum Power Point Tracking
PWM and MPPT are the two different types of charging methods solar charge
controllers can use to charge batteries from a solar array/panel. Both
technologies are widely used in the off-grid solar industry and are both great
options for efficiently charging your battery. The decision to use PWM or MPPT
regulation is not purely based on which power charging method is “better” than
the other. Moreover, it involves determining which type of controller will
work best in your system’s design. To understand the difference between PWM
and MPPT charging, let’s first look at a typical power curve of a PV panel.
The power curve is important because it states the expected power generation
of the panel based on the combination voltage (“V”) and current (“I”)
generated by the panel. The optimal ratio of current to voltage to produce the
most power is known as the “Maximum Power Point” (MPPT). The MPPT will change
dynamically throughout the day depending on irradiation conditions.
- Most often you can find the power curve for your PV panel on the product’s datasheet.
PWM Charge Controllers
Pulse-Width Modulation (PWM) comes into play when the battery bank is full. During charging, the controller allows as much current as the PV panel/array can generate in order to reach the target voltage for the charge stage the controller is in. Once the battery approaches this target voltage, the charge controller quickly switches between connecting the battery bank to the panel array and disconnecting the battery bank, which regulates the battery voltage holding it constant. This quick switching is called PWM and it ensures your battery bank is efficiently charged while protecting it from being overcharged by the PV panel/array. PWM controllers will operate close to the maximum power point but often slightly “above” it. An example operating range is shown below.
MPPT Charge Controllers
Maximum Power Point Tracking features an indirect connection between the PV
array and the battery bank. The indirect connection includes a DC/DC voltage
converter that can take excess PV voltage and convert it into extra current at
a lower voltage without losing power.
MPPT controllers do this via an adaptive algorithm
that follows the maximum power point of the PV array and then adjusts the
incoming voltage to maintain the most efficient amount of power for the
system. Pros and Cons of Both Types of Controllers
| PWM| MPPT
---|---|---
Pros| 1/3 – 1/2 the cost of a MPPT controller.| Highest charging
efficiency (especially in cool climates).
| Longer expected lifespan due to fewer electronic components and less thermal
stress.| Can be used with 60-cell panels.
| Smaller size| Possibility to oversize array to ensure sufficient charging in
winter months.
Cons| PV arrays and battery banks must be sized more carefully and may
require more design experience.| 2-3 times more expensive than a comparable
PWM controller.
| Cannot be used efficiently with 60- cell panels.| Shorter expected lifespan
due to more electronic components and greater thermal stress.
How to choose the right controller for your system
On the next page you will find an infographic flow chart that will help you
determine which type of charge controller is optimal for your specific
project. While there are many more variables to consider when determining
which controller is the best fit for your system, the infographic on the next
page aims to take some of the mystery out of the decision by addressing the
most important factors that need to be considered when making your decision.
For further support, please feel free to contact our technical department at:
tech.na@phocos.com.