The main function of a controller or regulator is to fully charge a battery without
permitting overcharge and at the same time preventing reverse current flow at night. Simple
controllers contain a transistor that shunts the PV charging circuit, terminating
the charge at a pre-set high voltage and, once a pre-set reconnect is reached, opens
the shunt, allowing charging to resume. More sophisticated controllers utilize pulse
width modulation (PWM) or maximum power point tracking (MPPT) to assure the battery
is being fully charged. The first 70% to 80% of battery capacity is easily replaced,
but the last 20% to 30% requires more attention and therefore more complexity.
How do solar regulators work?
The electronic circuitry in a controller monitors the voltage of the connected battery
and determines the state of charge of
the battery. As the battery nears full charge the amount of current flowing to
the battery is reduced until the battery reaches
its full state of charge.
Some solar controllers have advanced functions, these may include low battery disconnect,
timers and output control.
More expensive controllers have the ability to measure amps and battery state of
charge to give the user more control over
power usage and battery management.
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