Charge controllers are one of the most critical components of a solar power system. With the main purpose of protecting the batteries from overcharging, they ensure the efficiency and safety of the system as well as optimizing the lifespan of the system. Charge controllers are at the heart of the solar power installations as they usually link the solar panels and the batteries. Aside from overcharging, they also prevent battery drainage by shutting down the system if stored power falls below a certain threshold and start charging the batteries to safe and correct voltage level. Charge controllers are also acting as a valve by blocking reverse currents naturally passing some when solar panels have no energy supply at night. This will discharge batteries when controllers are not around.
We may see some installations that do not have a charge controller when supply of charge is small, typically with 1 to 5 watt solar panels. A safe ratio would be 2 watt solar panels supplying 50 Ah batteries. Beyond that, a charge controller is recommended.
There are two main types of charge controllers depending on efficiency, cost, lifespan. Pulse width modulation (PWM) charge controllers are cheap and simpler while the Maximum Power Point Tracking (MPPT) are more efficient. Both typically have a lifespan of 15 years.
- Pulse Width Modulation (PWM) charge controllers are the first controllers in the industry and are comparably simpler and cheaper. PWM reduces the current gradually by regulating the flow of energy to the battery. PWM controllers will keep supplying the batteries with a small amount of power when batteries are full. As the system uses only two-stage of regulating, the little energy use is recommended for small scale applications.
- Maximum Power Point Tracking (MPPT) charge controllers are efficient in terms of optimizing the supply from the solar panels to charge the batteries. Maximum power voltage of the panel is the basis when charging, while also minding the output limit to protect batteries from overcharging. MPPT’s asset is its monitoring and adjustment of input to regulate the current from the panels.
| Pulse Width Modulation (PWM) | Maximum Power Point Tracking (MPPT) | |
| Simplicity | ✅✅✅ | ✅✅ |
| Efficiency | ✅ | ✅✅✅ |
| Cost | ✅✅✅ | ✅ |
| Energy Usage | ✅✅✅ | ✅✅ |
| Application | Small scale | Large scale and critical |
Proper sizing is important for charge controllers taking consideration of the amount of power and currents produced by the solar panels.