4-1
Chapter 4 Solar Battery Charging
4.1
PWM Battery Charging
PWM (Pulse Width Modulation) battery charging is the most efficient and effective method
for recharging a battery in a solar system.
Selecting the best method for charging your battery together with a good maintenance
program will ensure a healthy battery and long service life. Although the SunStar’s battery
charging is fully automatic, the following information is important to know for getting the
best performance from your SunStar controller and battery.
4.1.1
Four Stages of Solar Charging
VOLTAGE
TIME
NIGHT
NIGHT
4
FLOAT
3
EQUALIZE
2
PWM
ABSORPTION
1
BULK
CHARGING
Figure 4.1.1 Solar Charging Stages
1. Bulk Charging:
In this stage, the battery will accept all the current provided by the solar
system.
2. PWM Absorption:
When the battery reaches the regulation voltage, the PWM begins to
hold the voltage constant. This is to avoid over-heating and over-gassing the battery. The
current will taper down to safe levels as the battery becomes more fully charged.
3. Equalization:
Many batteries benefit from a periodic boost charge to stir the electrolyte,
level the cell voltages, and complete the chemical reactions.
4. Float:
When the battery is fully recharged, the charging voltage is reduced
to prevent further heating or gassing of the battery.
4.1.2 Battery Charging Notes
The SunStar manages many different charging conditions and system configurations.
