Charge Controllers
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A charge controller is an electronic voltage regulator, used in off-grid systems and grid-tie systems with battery backup. It controls the flow of power from the charging source (such as solar panels, hydro plant, windmill) to the battery. The charge controller automatically reduces, stops, or diverts the charge when batteries become fully charged. It prevents overcharging and may prevent against overvoltage, which can reduce battery performance or lifespan, and may pose a safety risk. Charge controller capacities range from 4 amps to 80 amps and multiple charge controllers can be used in parallel for larger systems.
There are two types of charge controllers, known as Pulse Width Modulated (PWM) and Maximum Power Point Tracking (MPPT) charge controllers. The PWM charge controllers turn on and off rapidly, holding the batteries at full charge. They are a cheaper type. |
The MPPT charge controllers take power from the charging source at a voltage where it can put out the most power and convert that to the correct voltage to charge battery. Maximum power tracking allows a PV array (solar panels) to deliver up to 30% more power to a battery bank than it would if it were connected directly to be battery bank or if the PWM charge controller was used.
Most MPPT and some PWM charge controllers can take an array voltage much higher that what is required by the battery bank and step down in voltage to meet the battery bank voltage. For example, you can wire your solar array to 48 volts and yet have your battery bank be wired to 24 volts. A charge controller with a built-in step down function will take 48 volt charge and modify it to 24 volt charge. This saves a lot on wire costs. |
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