Charge Controller

What is a charge controller?

A charge controller is a device which limits the rate of charge or discharge of electrical energy from a battery. Also referred to as a charge regulator or battery regulator.

Key Takeaways:

  • Charge controllers are a critical part of solar power systems to prevent battery damage
  • There are three main types of solar charge controller systems
  • Charge controllers can be integrated with a battery or a stand alone device

Understanding charge controllers

A charge controller is the device which regulates the flow of power to and from a battery. In the context of a solar power system, a solar charge controller specifically manages the power going into the battery bank from the solar array to ensure that the batteries are not overcharged during the day and that they batteries do not drain at night when not in use. This is a particularly critical function as overcharging the batteries can reduce the battery life and pose a safety risk. 

Charge controllers can often also monitor battery temperature to prevent overheating, display data, transmit data to remote displays, and log data to track electric flow over time.

Charge controllers come in many shapes and sizes and may refer to either a stand-alone device or to an integrated system within a battery. However, when sold to consumers they are typically separate devices, often in conjunction with solar or wind power generators, for uses such as RV, boat, and off-the-grid home battery storage systems.

Simple charge controllers work by simply shutting off the battery charging when they exceed a set voltage level and then re-enables charging when the voltage drops back below that level. While, a shunt charge controller will divert the excess power generated to an alternate system such as an electric water heater when batteries are fully charged.

Charge controllers come in three main types:

1 or 2 Stage Controllers – These charge controllers rely on shunt controllers and are fairly simple in design.

3 Stage Controllers – These are the industry standard and typically use a technology called Pulse Width Modulation (PWM). These directly connect from the solar array to the battery bank and rely on correctly balancing the voltage generated by the panels and the capacity of the batteries to maximize efficiency.

Maximum Power Point Tracking (MPPT) – MPPT solar charge controllers measure the voltage generated by the solar array and will convert this as needed to match the battery bank voltage. Because this allows for more efficient charging, these systems are able to achieve up to 98% efficiency and provide up to 30% more power to the battery.

Related Terms

Battery – A storage device for electrical energy, typically in a chemical solution, that can be used as a source of power.

Battery Cycle Life – The typical number of charge and discharge cycles that a battery can undergo before it reaches the end of its useful life.

Battery Life – The length of time a device can continue to work before it needs its battery to be recharged.