charge control systems
When using PV panels as part of an off-the-grid or hybrid system it
is usually necessary to use an electrical devices called a charge controller.
A charge controller helps to manage the voltage of the system and to manage the charging of
the batteries. If a battery is routinely allowed to overcharge its
life expectancy will be greatly reduced. A modern Pulse Width
Modulated (PWM) controller can turn on and off the circuit that
connects to your batteries and PV units in order to keep the voltage
more stable. If the charge in the battery gets too high it can cut the
circuit to avoid overcharging.
Some charge control systems are designed so that they will run the
system at whatever voltage produces the most wattage. A good
controller can sometimes increase the amount of usable energy you get
out of your PV panels and batteries by as much as 15%.
In order to be effective a charge controller must be matched to the
type of batteries you are using. For example a charge controller designed for lead-acid batteries should not be used to control
Also the charge controller must be of the right capacity to handle the
maximum current produced by the PV array.
There are two types of controllers: series and shunt. Series controllers stop the flow of current by opening the circuit between the battery and the PV array. Shunt controllers divert the PV array current from the battery,
sometimes to an artificial load. Both types use solid state battery voltage measurement devices and shunt controllers are 100% solid state.
Several charge controllers on the market use a 3 stage charging
approach with bulk, absorption, and float modes to ensure that
voltage and current settings accurately match the batteries' actual
state of charge. This reduces the time needed to bring the battery to
full charge and can extend the life of the battery.