Samlex America SCC-30AB - Manuel (Page 8)

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General Description of solar system
The output current of the Solar Cell has a Positive Temperature Coefficient – the
output current increases with the rise of temperature. However, it is negligible – less
than 0.1 % / °C of the Short Circuit Current Isc.
The output Voltage of the Solar Cell has a Negative Temperature Coefficient – The
output Voltage increases with decrease in temperature. For example, a Silicon Cell has
a Temperature Coefficient of – 2.3 mV / °C / Cell. Hence, during cold winter days, the
voltage will rise.
As a Rule of Thumb, the voltage rating of the Charge Controller should be
sized as 1.25 times the Open Circuit Voltage rating Voc of the Solar Panel to ensure that the
Charge Controller is not damaged due to over voltage.
Battery Types
There are several different types of battery chemistries like Lead-Acid, Nickel-Iron
(Ni-Fe), Nickel-Cadmium (Ni-Cad) etc. Batteries consist of individual cells connected in
series to obtain the required Battery Voltage. Batteries are either sealed (also called
Valve Regulated Lead Acid - VRLA) or non-sealed / vented / flooded / wet cell.
Nickel-Iron (Ni-Fe) and Nickel-Cadmium (Ni-Cad) Battery
Nickel-Iron (Ni-Fe) and Nickel-Cadmium (Ni-Cad) (also called alkaline batteries) have a
nominal cell Voltage of 1.2V per cell. The nominalVoltage of a Ni-Cad / Ni-Fe battery
bank can be made the same as a lead acid bank just by juggling the number of cells
(10 cells for 12V, 20 cells for 24V and 40 cells for 48V systems). However, the Ni-Cad /
Ni-Fe battery bank must be charged to a higherVoltage to fully recharge and will drop
to a lower voltage during discharging compared to a similarly sized lead acid type
battery.
Lead Acid Battery
A Lead Acid battery consists of a number of 2V nominal cells (actual voltage of the
cell is 2.105V) that are connected in series e.g. a 12V nominal battery will have six, 2V
nominal cells in series (actual voltage of the 6 cells will be 2.105 x 6 = 12.63 ).
Each 2V nominal cell in this battery consists of an independent enclosed compartment
that has Positive and Negative Plates (also called Electrodes) dipped in electrolyte
that is composed of diluted Sulphuric Acid – solution of 33.5% v/v Sulphuric Acid and
water.
*The Positive and Negative electrodes may be made of flat plates, or may be made in a
spiral roll form to make cyclindrical/tubular cells. In a fully charged battery, the Positive Plate is in
the form of Lead Dioxide, the Negative Plate is in the form of Lead and the Sulphuric Acid in the
electrolyte has the maximum concentration of 33.5% v/v.
Construction of Battery Cell Plates -
Lead Antimony and Lead Calcium Batteries
During construction, both the Positive and the Negative plates are similar.
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GENERAL INFORMATION: BATTERIEs