Modern multi-stage charge controllers Most quality charge
controller units have what is known as a 3-stage
During this phase of the charge cycle, the voltage gradually
rises to the bulk level (usually 14.4 to 14.6
volts for 12volts batteries) while the batteries draws maximum current. When Bulk level voltage is reached
the absorption stage begins.
During this phase the voltage is maintained at bulk voltage
level for a specified time (usually an hour)
while the current gradually tapers off as the batteries charge up.
After the absorption time passes, the voltage is lowered to
float level (usually 13.4 to 13.7 volts for 12volts
batteries) and the batteries draw a small maintenance current until the next cycle starts.
MPPT MAXIMUM POWER POINT TRACKING DESIGN
The new maximum power point tracking (MPPT) controllers
improve on past designs in many ways. They match
the output of the solar panels to the battery voltage to ensure maximum charge (amps). For example, even though
your solar panel is rated at 100 watts, you won't get the full 100 watts unless the battery is at optimum voltage.
The power/watts is always equal to volts * amps, or P=E*I (see Ohm's law for more info). With a regular
charge controller, if your batteries are low at say 12.4 volts, then your 100 watt solar panel rated at 6 amps at 16.5
volts (6 amps times 16.5 volts = 100 watts) will only charge at 6 amps times 12.4 volts - or just 75 watts, sacrificing
25% of total capacity. The MPPT controller compensates for the lower battery voltage by delivering closer to
8 amps into the 12.4 volt battery maintaining the full power of the 100 watt solar panel. (100 watts = 12.4 volts
times 8 amps = 100 (P=E*I)) This product comes with various system voltages from 12V/24V/48V/96V/120V.
the battery from overcharging and deep discharging in order to ensure a long battery life. Since the brighter the
sunlight,the more voltage the solar cells produce, excessive voltage could damage the batteries. A charge controller
is used to maintain the proper charging voltage on the batteries. As the input voltage from the solar array rises,
the charge controller regulates the charge to the batteries preventing overcharging.