Basics Equipment Charge Controllers
Charge Controllers
Charge controllers control the charging of batteries. They keep the battery from being over charged. Like inverters, most charge controllers have maximum peak power tracking (MPPT) which keeps the solar array operating at the maximum power point. The array voltage normally has to be higher than the battery bank voltage for charge controllers to work.
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Most charge controllers have what is called three-stage charging, which is a more efficient way of charging batteries. The battery can accept more current when it is discharge. The first stage is called bulk charging and the current is high, the maximum the battery can take or the maximum the solar array can provide. The second stage is called acceptance and is a gradual tapering off of the current as the battery becomes charged. The last stage is called float and is just enough voltage to top off the battery and keep the battery from discharging. Three-stage charging saves money because a smaller array is needed.
There are many variations of charge controllers and many available features. Ground fault protection devices protect the array from catching fire if there is a ground fault. Diversion charge controllers will divert excess energy to do useful work such as heating water. Multiple-source charge controllers will accept energy from different sources like a wind turbine or generator and can even start the generator if the battery voltage falls below a set point. Most charge controllers come with some sort of display to show the system status.
More about charge controllers is in the Solar Basics book and how to size a charge controller is in the Solar Design book.