PWMs Charge Controllers ensure efficient charging and discharging of system battery (or a bank of batteries). PWMs help to regulate the often inconsistent voltage put out by power sources (for example, solar panels) in order to protect the system batteries from overcharging. When a solar array has the PWM mode activated, the charge controller uniquely handles the job of battery charging by constantly checking the current battery state and self-adjusting accordingly to send only the right amount of charge to the battery.

In essence, this type of charge controller works by reducing the current from the power source according to the battery’s condition and recharging requirements, which is in contrast to on/off charge controllers which suddenly cut off power transfer to minimize battery overcharging. The PWM charge controller does this by checking the state of the battery to determine both how long (wide) the pulses should be as well as how fast they should come.

With that information, the PWM charge controller then self-adjusts and sends the appropriate pulse to charge the battery – it varies the length and speed of the pulses sent to the battery as needed (see Figure). This is essentially a rapid on and off switch. When the battery is nearly discharged, the pulses may be long and continuous, and as it becomes charged, the pulses become shorter or trickled off. This trickle or finish type charging mode is important for systems that can go days or weeks with excess energy during periods when very little of the solar energy is consumed.

This type of charge controller is ideal for solar arrays where excess energy is a regular occurrence, and provide several key benefits: higher charging efficiency, rapid recharging, and healthier batteries that operate at full capacity.