Solar Primer continued...
Panel Performance Specifications:
Panels are usually rated at 25 degrees Celsius (80 F) and 1,000
Watts per square meter of solar radiation. Specifications are always
given in Watts which is the panel's Amperage x Panel Voltage.
THE BASIC EQUATION: Watts = Volts x Amps
- Amperage indicates how fast the panel will charge a battery
(i.e. water flow).
- Voltage indicates the force behind the charge being applied to
the battery. (i.e. water pressure)
- Wiring in parallel (+ to + and - to -) will add current and keep
voltage constant
- Wiring in series (+ to -) will add voltage and keep current constant
Panel voltage is typically between 14.5 and 17 volts. Panels above
15.6 volts will require a charge regulator to properly apply the
panel's power to the batteries for optimal and efficient charging.
Panels with voltages below 15.6 are often called self regulating
panels and can only be used in cooler climates as all panels' voltage
will drop as the temperature rises above the rated 25 degrees and
these low voltage panels will not be able to properly bring a battery
up to full charge. Battery capacity & usage patterns are also
issues with "self-regulating" modules.
Charge Regulators (or charge controllers)
Charge regulators have the basic function of preventing solar panels
from overcharging the batteries. Two major types exist:
- Series: Opens a relay when batteries are full to prevent any
more current flow. Pulse width modulated regulators will send
a series of electronically controlled pulses to the batteries
to maintain a full state of charge.
- Shunt: Diverts current to a resistive load when batteries reach
full state of charge (wind generators)
The capacity of a regulator determines how many panels can be wired
to it, and the amount of loads which can be wired to it for load
control features. I.e. a 10 amp, 12 volt regulator may have up to
10 amps of panels (wired together for 12 volts) connected to it -
two SP75 4.4A panels = 8.8A at 12V.
Other standard features of regulators include:
- Reverse polarity protection - protects against damage caused
by incorrect wiring
- Blocking diode - prevents current from flowing backwards from
battery to panel to space at night.
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