Solar Charge Controller

Solar Controller

solar street light 15 watt

Solar charge controllers or regulators are devices used in solar-powered lights to regulate the electric current flowing from the solar panel to the battery.  Solar controllers are also responsible in limiting the current drawn from battery to the LED.  In a solar lighting system, controllers play an important role in managing charge and voltage.  When the solar panels stop generating power at sunset, controllers help turn the LED.

There is a possibility of electricity flowing backwards from the battery to the panels when no current is produced at night, which can harm the life of the batteries.  Charge controllers help in preventing this reverse power flow by detecting when there is no power generation and disconnecting the panels from batteries to avoid overcharging.  Overcharging can also reduce the life of batteries and modern charge controllers help in extending battery life by reducing the amount of current applied to the battery when it is fully charged and also assist in converting excess voltage into amperage.

Why are controllers required in solar lights?

  • To regulate battery voltage
  • To prevent reverse current flow
  • To avoid overcharging and undercharging of batteries
  • To indicate when battery is charged

Types of solar charge controllers 

Pulse Width Modulation (PWM) charge controllers

PWM is the most commonly used controller as it uses time-tested technology to regulate the flow of current.  Pulse width modulation happens when the battery reaches a balanced charging stage by reducing the current gradually.  Self-discharge is a common problem in most rechargeable batteries where they tend to lose power once they are fully charged.  PWM controller resumes to supply a small amount of power constantly in order to keep the battery charge full and maintains the charge, thereby avoiding self-discharge.

PWM controllers are considered to be very durable and perform well in warmer climates.  They are relatively less expensive and are available in many sizes for a variety of applications.  With PWM controllers, it is important to have solar panels and batteries with matching voltages.  PWM charge controller is the standard type charge controller used in solar street light and is also well suited for small solar systems with small panels and battery.

Maximum power point tracking (MPPT) charge controllers

MPPT controllers are a more expensive and complex option for solar systems; however, one of the biggest advantages of these controllers is unlike PWM controllers, MPPT controllers can match non-matching voltages from solar panels and batteries.  The technique used in MPPT controllers is new that enables the panels to operate at their maximum power point.  Because of the varying degree of solar radiation throughout the day, the panel voltage and current may vary.  MPPT controllers adjust the voltage in order to generate maximum power no matter what the weather conditions are.

MPPT controllers charge faster and have a longer lifespan.  They are able to adjust their input to initiate maximum power possible from the panels.  These controllers are capable of varying the output power to match the battery power.  They are observed to work better in cold climates and are considered to be more efficient than PWM controllers.

How to choose the right charge controller?

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Both PWM as well as MPPT charge controllers are used in a solar street light system.  Controllers serve as a protective device and bring out the best from your solar unit.  Based on the following factors, you must choose a controller that is compatible with your solar system voltage.

Total lifespan of the controller

Location of installation and its temperature conditions

Your energy requirements and budget

Efficiency of solar panels

Overall size of the solar light system

Battery type used in the solar light system