solar charge controllers

A charge controller is also known as charge regulator or battery regulator. They are used to limit the rate at which electric current is drawn from batteries.

What are solar charge controllers?

Solar charge controllers are devices that regulate current from a solar panel to battery in order to charge it and also regulate current from battery to a light source such as LED to illuminate it. Solar charge controllers play an important role in solar light system installation.

Why are charge controllers required in a solar light system?

Controllers manage charging of batteries and when there is no power generated, they turn on the LED. At night when electricity is not produced anymore, there is a possibility for the stored electricity to flow backwards from the battery to the solar panels. This can drain the batteries and a solar charge controller can prevent this reverse power flow. Solar charge controllers disconnect the solar panels from batteries when they detect there is no power generation by the panels and thereby avoiding overcharging.

Overcharging can markedly cause reduced battery life and sometimes complete damage to the batteries. Modern solar charge controllers help in extending battery life by lowering the amount of power applied to the batteries when the batteries are almost fully charged and convert excess voltage into amperage.

Solar charge controllers are required because:

  • They give clear indication when the battery is charged
  • They stop the battery from overcharging and undercharging
  • They regulate the voltage of the battery
  • They block backflow of current

Types of solar charge controllers

Pulse Width Modulation (PWM) charge controllers:

These controllers use a technique that regulate the flow of current to the battery by reducing the current gradually which is known as pulse width modulation. When the battery is full and reaches a balanced charging stage, the controller continues to supply a small amount of power to keep the battery charge full. Most rechargeable batteries tend to self-discharge and lose power even after being fully charged. PWM controller maintains the charge by continuing to supply a same small current as of the self-discharge rate.


  • Less expensive
  • Older and time tested technology
  • Durable and performs well in warmer temperature
  • Available for a variety of applications in many sizes


  • Only 65% to 75% efficiency
  • Solar input voltage and nominal voltage of battery should match
  • Not compatible for higher voltage grid connect modules

Maximum power point tracking (MPPT) charge controllers:

These controllers use a technique to enable the solar panel to operate at its maximum power point. Solar panel receives varying degree of sunlight throughout the day and this can cause the panel voltage and current to continuously change. MPPT helps to track and adjust the voltage to generate maximum power irrespective of the weather conditions.


  • Charge faster and longer lifespan
  • More efficient than PWM
  • Latest technology
  • Conversion rate can go up to 99%
  • Works better in cold climates


  • Expensive
  • Larger in size compared to PWM

How to choose the right charge controller?

Based on the current capacity, a solar charge controller which is compatible with the system voltage should be selected. MPPT controllers are commonly used in solar street lights. Solar charge controllers are considered a protective device and bring out the best from your solar street light. The factors to keep in mind while choosing the appropriate controller are:

  • Lifespan of the controller
  • Temperature conditions where the solar system will be installed
  • Your energy needs
  • Number of solar panels and their efficiency
  • Size of your solar light system
  • Type of batteries used in the solar light system

Technical specifications such as components used, their efficiency and lifespan are given in detail with each solar light system. Based on your budget, features you require and location of installation, you may choose the controller that is right for your solar lights.