CHARGE CONTROLLER

Charge controllers are used in photovoltaic, wind turbine and electric charging power systems that use batteries. The basic function of a charge controller is to monitor the charging and discharging of the battery. It prevents the battery from being completely overcharged or discharged. This is necessary because overcharging can result in the destruction of the battery and undercharging will ultimately result in short battery life. Also another important consideration in the use of charge controllers is their use help in preventing a reverse flow of current to the DC source.

There are different types of charge controllers and they are , ON/OF ,shunt, series, pulse width  modulation (PWM), maximum power point tracking (MPPT), DC -DC and smart controllers.

ON/OFF charge controllers use a simple voltage threshold to determine when to turn the charging process ON or OFF. Thus when the battery voltage is low (i.e. it needs charging) the switch turns on and energy flows from the solar or wind turbine power system to the battery. When the battery voltage is high (i.e. it is charged) the switch turns off and the charging process stops. . They are inexpensive, easy to install and maintain. On the other hand, they can overcharge or undercharge batteries and lack precision in voltage regulation. Thus they find application only in small solar, wind turbine and electric power charging systems

Shunt charge controllers diverts excess energy from the solar panel or wind turbine away from the battery when it is fully charged. The controller monitors the battery voltage and current and when the battery is fully charged the controller diverts or shorts the excess energy from the battery. Shunt charge controllers prevents overcharging as well as other types and in addition they are low cost, efficient and easy to install. On the other hand they waste excess energy rerouted if not used adequately and are not considered suitable for large scale solar , wind turbine or electric charging power systems.

Series charge controllers use a series switch typically a transistor or relay to connect and disconnect the solar, wind turbine or electric charging power system from the battery using a voltage sensor which monitors the battery voltage and provides the necessary feedback to the controller. They are considered to be efficient in their operation and are cost effective. On the other hand they have limited flexibility, no overcharging and short circuit protection. They find use in small solar, wind turbine and electric charging power system.

Pulse width modulation charge (PWM) controllers regulate the flow of energy from an energy source like a solar and wind turbine system to a battery by adjusting the width of the charging pulses. PWM controllers use a complex algorithm to adjust the width of the charging pulses based on the battery state of charge, temperature and other factors. Pulse width modulation (PWM) charge controllers simulates a lower current level by pulsing a higher current level on and off for short intervals. Pulse width modulation is the process of modifying the width of the pulses train in direct proportion to a small control signal. The greater the control voltage the wider the resulting pulses become, pulse width modulation charger is set to match the input power of the battery irrespective of the power generated by the solar panel or the electric charging power system because of this there is an inherent loss of power associated with these type of chargers.

They are more efficient than the simple ON and OFF, shunt and series charge controllers. They can also be programmed for a specific battery type and are relatively inexpensive. On the other hand they can still overcharge or undercharge batteries if they are not properly configured and may not be suitable for large scale systems. They find application in medium sized solar, wind turbine and  electric power charging systems.

Maximum power point tracking (MPPT) charge controllers regulate the flow of energy from a solar, wind turbine or DC electric charging power source by tracking the maximum power point of the energy source. The MPPT controllers use advanced algorithms and sensors to track the maximum power point of the energy source and adjust the charging process accordingly. They do this by applying the maximum power point theorem, which states that the output power of a circuit can be maximized by adjusting the source impedance equal to the load impedance, so the MPPT algorithm is equivalent to the problem of impedance matching. This is done by utilizing a boost converter whose duty cycle is varied by using a MPPT algorithm. Thus the MPPT charger helps to get the optimum charging power for any given point of time and offers a better efficiency than PWM chargers.

They have a very high efficiency of up to 98% in their operation. They can handle high power inputs and optimize greatly the batteries lifespan.

On the other hand they are more expensive than PWM controllers and they require complex installation and configuration. They find widespread use in large scale solar and wind turbine power system. They are also used as battery charging systems for electric vehicles.

Smart charge controllers integrate advanced features such as WI fi connectivity, Bluetooth connectivity and mobile apps control to monitor and control the charging process. Smart controllers use advanced algorithms and sensors to monitor the charging process and adjust accordingly. They also communicate with the user through mobile apps or web portals. Smart controller’s main advantages over other controllers are that they operate using in addition to the basic function, remote monitoring and control systems. They also incorporate advanced charging algorithms and integration with energy storage system and grid tie inverters. On the other hand they are more expensive than traditional charge controllers and they require complex installation and configuration. They have found widespread use as controllers for residential and commercial solar and wind power systems

DC-DC charge controllers regulate the flow of energy from a DC energy source like a solar panel or a wind turbine power system to a battery by converting the input voltage to a stable output voltage. DC –DC   controllers use switching regulators to convert the input voltage to a stable output voltage. They have efficiencies of up to 98% in their operation and they have a wide input voltage operating range.

On the other hand they are more expensive than traditional charge controllers and they require complex installation and configuration.

They find widespread use as charge controllers for solar and wind turbine power systems with large load or high input voltage requirements and as controllers for electric vehicle charging power systems.

Generally charge controllers find the most applications and use in the following; solar power systems, wind power systems, hydro power systems, off-grid and grid-tie power systems, electric charging power system and telecommunication systems.

The future of charge controllers is based on the following trends and developments in technology; the increased adoption of renewable energy, advancement in power electronics, energy storage systems, smart charging and grid management, electric I vehicle charging infrastructure and advanced materials, grid-tie and off-grid capabilities, artificial intelligence, IoT and remote monitoring.

These trends and development will shape the future use of charge controllers, enabling more efficient, robust, resilient and sustainable energy systems.

 

SOURCES;

• Solar electricity handbook by Michael Boxwell.
• The solar bible by Christopher Laughton.
• Solar charge controllers: A comprehensive guide by M.A, Elgendy.
• Renewable energy and power electronics by R. Belaidi and A.T Elsayed.
• Solar power system design and installation by Erik W. Gunther.