What is a charge controller?

Charge controller is a device preventing batteries from overcharging and overdischarging. One of the most common problems of batteries is that they cannot be discharged excessively or recharged too often. A charge controller controls the charge by managing properly the battery voltage and current.

Charge controllers (like RENOGY 40 AMP MPPT CHARGE CONTROLLER ) are intended to protect the battery and to deliver it as longer life as possible, while keeping the photovoltaic system efficiency. It should be noted that charge controllers only control DC loads. AC loads are to be controlled (and disconnected, if needed) by an inverter.

The key functions of charge controllers are:
Protecting the battery from overcharging by limiting the charging voltage
Protecting the battery from deep and/or unwanted discharging. The charge controller automatically disconnects the loads from the battery when battery voltage falls below a certain depth of discharge value
Preventing the reverse current through PV modules at night
Providing information about battery state of charge


The main charge controller types available today are PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking) ones. MPPT charge controllers are more expensive but they can boost the performance of the solar array. PWM charge controllers are less expensive but they can extend battery bank’s lifecycle at the expense of solar panels performing lower than in case of MPPT controller. Similar to inverters, charge controllers have a lifespan of about 15 years.


A charge controller costs between $500 and $1,000. (However, you can find some low grade PWM charge controllers for about $30-$50).


This is not a fortune but not choosing the proper charge controller for your system might results in series of problems. Your solar system might either underperform or not work at all. The worst however is that other system components might get damaged.


Therefore selecting charge controller should not be underestimated.


What kind of charge controller to choose depends on the specific case and is a tradeoff between getting more power from solar panels and extending battery life.


To get an idea what controller you need for your system you need neither dig into heavy science nor be a solar guru.


You just have to know some basic info such as:


– Which type of charge controller is recommended for a given solar system type


– What maintenance a charge controller needs and how much are its annual maintenance costs


– When you need a couple of charge controllers rather than a single one


– Which charge controller type is recommended for hot climates


– What controller to select for a small solar system


– What controller you need to connect a 48V-solar array to a 24V-battery bank