Charge controllers are sold to consumers as separate devices, often in
conjunction with solar or wind power
generators, for uses such as RV, boat, and off-the-grid
home battery storage systems. In solar applications, charge controllers
may also be called solar regulators. Some
charge controllers / solar regulators have additional
features, such as a low voltage disconnect
(LVD), a separate circuit which powers down the load when the batteries become
overly discharged (some battery chemistries are such that over-discharge can
ruin the battery).
A series charge controller or series regulator disables
further current flow into batteries when they are full. A shunt charge
controller or shunt regulator diverts excess electricity to an
auxiliary or "shunt" load, such as an electric water heater, when
batteries are full.
Simple charge controllers stop charging a battery when they exceed a set
high voltage level, and re-enable charging when battery voltage drops back
below that level. Pulse width modulation (PWM) and maximum power point tracker (MPPT)
technologies are more electronically sophisticated, adjusting charging rates
depending on the battery's level, to allow charging closer to its maximum
capacity.
A charge controller with MPPT capability frees the system designer from
closely matching available PV voltage to battery voltage. Considerable
efficiency gains can be achieved, particularly when the PV array is located at
some distance from the battery. By way of example, a 150 volt PV array
connected to an MPPT charge controller can be used to charge a 24 or 48 volt
battery. Higher array voltage means lower array current, so the savings in
wiring costs can more than pay for the controller.
Charge controllers may also monitor battery temperature to prevent
overheating. Some charge controller systems also display data, transmit data to
remote displays, and data logging to track electric flow over time.
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