What is the different from PWM and MPPT Solar Controller Working Function?

 PWM and MPPT Solar Controller


  • How to Make Solar Controller Work A Solar controller, or solar regulator is similar to the voltage regulator in your car.
  • It regulates the voltage and current coming from the solar panels that go to the battery.
  • Most “12 volts” panels put out about 16 to 20 volts, so if there is no regulation the batteries will be damaged by overload. Most batteries need about 14-14.5 volts to fully charge.
  • Not always, but usually. Generally, there is no need for a solar controller with small maintenance, or slow load panels, such as solar panels from 1 to 5 Watts.
  • An approximate rule is that if the panel puts out about 2 watts or less for every 50 amp-hours, then you do not need one.

Different from PWM and MPPT Solar Controller?

PWM Solar:

  • Very few load controls have a “PWM” mode. PWM stands for Pulse Width Modulation.
  • PWM is often used as a method of loading the float.
  • Instead of a constant output from the controller, it sends a series of short charge pulses to the battery – a very fast on-off switch.
  • The controller constantly checks the battery status to determine how fast to send pulses, and how long (width) the pulses will be. On a fully charged, uncharged battery, you can just “flag” every few seconds and send a short pulse to the battery.
  • On a discharged battery, the pulses would be very long and almost continuous, or the controller could go into “full on” mode.
  • The controller checks the battery charge status between the pulses and adjusts each time.

MPPT Solar Controller:

  • MPPT Schematic Solar Controller
    A maximum power point tracker or (MPPT) is a high-efficiency DC to DC converter that functions as an ideal electrical charge for a PV cell, most commonly by a panel or solar panel and converts the power of a voltage level or which is more suitable for whatever the system load is designed to drive.
  • The most basic MPPT solar controller simply monitors the battery voltage and opens the circuit, preventing charging when the battery voltage rises to a certain level.
  • Older MPPT charge controllers used a mechanical relay to open or close the circuit, stop or power goes to the starting batteries.
  • More modern MPPT charge controllers use pulse width modulation (PWM) to slowly reduce the amount of power applied to the batteries as the batteries get closer and closer to fully charged.
  • This type of MPPT controller allows the batteries to be fully charged more with less stress on the battery, extending battery life.
  • It can also keep the batteries in a fully charged state (called “float”) indefinitely. PWM is more complex but does not have any mechanical links to break.
  • The latest and best type of  Solar Controller is called Maximum Power Trace or MPPT. Solar MPPT controllers are basically capable of converting the excess voltage into amperage.
  • This has advantages in a couple of different areas.
  • Most solar power systems use 12-volt batteries, as you find them in cars. (Some use other voltages and the same advantages apply to these systems as well.) Solar panels can provide much more voltage than is needed to charge the batteries.
  • By essentially converting the excess voltage into amperes the charge voltage can be maintained at an optimum level while the time required to fully charge the battery is reduced.
  • This allows the solar power system to function optimally at all times.
  • Low voltage on the wires that run from the solar panels to the load controller results in greater loss of power in the wires than a higher voltage.
  • Using an MPPT controller allows the much higher voltages in the panel wires to the Solar Controller.
  • The MPPT controller then converts the excess voltage into additional amplifiers.
  • MPPT load controllers are more expensive than PWM load controllers, but the advantages are worth the cost.
  • If you can afford it, you should definitely use a Solar MPPT controller.
  • The latest function of modern solar controllers is preventing the reverse flow of current.
  • At night, when solar panels are not generating electricity, electricity can actually flow back from the batteries through the solar panels, draining the batteries.
  • You’ve worked hard all day using solar power to charge the batteries; you do not want to waste all that power!
  • The charge controller can detect when no power is coming from the solar panels and open the circuit, turn off the solar panels from the batteries and stop the reverse current flow.