What is the difference between MPPT& PWM Charge controllers

What are solar charge controllers?

The solar charge controller sits between the energy source and storage and prevents overcharging of batteries by limiting the amount and rate of charge to your batteries. They also prevent battery drainage by shutting down the system if stored power falls below 50 percent capacity and charge the batteries at the correct voltage level. This helps preserve the life and health of the batteries.[1]

#1 MMPT solar charge Controller

MPPT solar charge controller It is a charge regulator used to regulate the incoming voltage from solar cells and has several advantages over the PWM charging system, as it invests the electrical energy out of the solar energy at full capacity in charging the batteries without the presence of wasted energy.

At the beginning, to understand the topic more, it is necessary to mention the difference between charging using the PWM method and charging using the method of MPPT:

  1. BWM solar charge controllers take only the voltage required to charge the battery from the solar module and leave the excess voltage without investment.
  2. PWM charge controllers are cheap compared to MPPT charge controllers.
  3. PWM are widely used in solar systems of less than 2 kilowatts due to the price difference between them and MPPT charging regulators.
  4. PWM uses Pulse Width Modulation technology, thus helping to increase battery life by breaking down sulfate deposits on lead sheets.

To understand why we recommend MPPT charge controllers, it is necessary to give a practical example:

Example 1️⃣:

If we connect a 30-volt solar panel to a PWM-type charg regulator to abattery of a 12-volt type, in this case the charger takes approximately 15 volts from the module and charges the battery with it and leaves the remaining 15 volts from the solar panel without investment.

Whereas, MPPT charg controllers take the necessary voltage to charge the battery and convert the excess voltage into current (via a voltage converter) in order to speed up the battery charging process and more efficiently (reduces the panel voltage at the expense of raising the charging ampere).

Example 2️⃣:

let’s Suppose we have a 30 volt /200-watt solar panel and we want to charge a 12-volt battery with it, since the panel is 30 volts and the power is 200 watts then the output current is 6.6 amps (200/30 = 6.6) because the current equals the power divided by the voltage.
In this case, if we connect the solar panel to the PWM charge controller, it will charge the battery with a voltage of approximately 15 volts and leave the remaining voltage which is also 15 volts.

The charging current in this case will be only 6.6 amps. Thus, the power used to charge the battery is equal to 6.6 * 15 = 99 watts only, while if we connect the same previous solar module to the same previous battery, but this time using an MPPT charger that charges the battery with a voltage of 15 volts and then transforms the remaining voltage of 15 volts into a current, the charging current becomes (200/15) 13.3 Ampere.

Example 3:

If I had a 150-watt solar panel and I have a 100-amp battery, and I used a PWM charge controller (the module is known to be 18 volts) and the voltage needed to charge the battery to the upper limit is 14.6 volts, of course, the PWM charge controller reduces the charging voltage from 18 volts to 14.6 or 14.4 volts and the ampere, of course, is the ampere of the module as it is 8.33 amps, That means I will have 3.4 volts of unused excess voltage.
(18-14.6 = 3.4v)
But if you use MPPT, this excess voltage will appear as amperes in charging the battery.
The charging amp will be in the case of the MPPT regulator:
150W / 14.6V = 10.27A

Compared with the PWM which gives only 8.33 amperes and thus the performance difference between the two types of solar regulators will be:

10.27 / 8.33 = 1.23

This means a 23% performance difference between the regulators
On the one hand, the panels are connected in series (series) in the MPPT regulator thus providing the cable size, unlike the PWM.

Related posts : what are the 3 types of charge controllers ?

How to convert voltage to current?

There is a general rule in the science of electronics and electricity that says it is impossible to raise the voltage except at the expense of the current and vice versa, so the current cannot be raised except at the expense of the voltage, and this is what MPPT type charging regulators do, as they raise the current at the expense of the voltage, but in both cases, the power ( Capacity) remains the same.
Voltage and current are two parts that do not separate, so by changing one of them, the other changes (considering the power is constant).
It is on this base that the voltage is converted to current in MPPT charging regulators

# When to use MPPT and when to use PWM?

# MPPT trucks are often used when:
1) There is a large voltage difference between the solar panel voltage and the battery voltage, thus there is large energy waste.
2) The system size is large (greater than 2000 or 3000 watts), so raising the current a little help dispense with purchasing additional solar panels.
3) MPPT is preferred in cold regions because in cold climates the voltage of the panels is increased, and this increase is exploited by the MPPT and turns it into an ampere that charges the batteries.

# PWM charge controllers are often used in the following situations:

  1. The voltage of the solar panel is close to the battery voltage, so there is no big waste of energy.
  2. The system size is small (less than 2000 watts).

[1] : Reongy

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