Charge Controller

A charge controller protects the batteries of a solar power backup system.  It prevents the batteries from being overcharged by the solar panels and limits how much current is drawn from the batteries. Batteries that are overcharged and discharged excessively tend to have short lifetimes.

There are two types of controllers:

  • Stand-alone controllers - this type of controller is usually a separate device or module that is used with solar and wind generators. Solar panel controllers can be used with off-the-grid home solar power backup systems.
  • Integrated controller - this type of controller is usually built into electrical circuitry for rechargeable devices such as cell phone chargers, and portable electronic devices. Integrated current regulators do pretty much the same as stand-alone controllers in that they protect the battery or batteries being charged.

Controllers work in a three stage cycle:

  1. The BULK stage - during this stage the controller allows the batteries to take in maximum current, usually close to 14.5 volts.
  2. The ABSORPTION stage - the absorption stage is where voltage is kept at about 14.5 volts for about an hour as the current slowly decreases.
  3. The FLOAT stage - the float stage is where the controller allows the voltage to decrease to about 13.5 volts with a very small current to keep the battery "topped off" until it is needed again.

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