Lamar Technologies BETA D-50 - Manual (Page 32)

APPENDIX A - BATTERY OVERVIEW
APPENDIX
APPENDIX A - BATTERY OVERVIEW
CLASSES OF BATTERIES
Batteries can be divided into two major classes: primary and secondary. The primary
batteries are not practically reusable once its useful energy has been discharged. The
secondary battery is rechargeable. In the following only secondary batteries will be covered.
SECONDARY BATTERIES
Secondary batteries differ from primary batteries in that they may be recharged. Some of the
materials in the cells of primary batteries are usually consumed in the process of changing
chemical energy into electrical energy. In the secondary system, the materials are transferred
from one electrode to the other as the cells discharge. The cells are restored to their original state
of charge by forcing an electric current through the cells in a direction opposite to that of the
discharge. These batteries are used in a multitude of applications ranging from
megawatt sizes in submarines to milliwatt sizes in portable radios.
LEAD-ACID BATTERIES, VENTED OR SEALED (SLAB)
The lead-acid battery is a rechargeable system using acid electrolyte (sulfuric acid and
water). Lead-acid batteries may be vented or sealed. The advantages of lead-acid batteries are
that they have a low initial cost, require low maintenance, and their discard cost is low. The
SLAB, on a per-weight basis, provides as much power as a nickel-cadmium battery. Lead-acid
batteries shed active material from the positive plate, proportional to the number of
charge/discharge cycles. This results in diminishing battery performance with age and loss of
active material on the positive plates due to the washing action of the gas bubbles
generated during charge. The open circuit voltage of a fully charged cell is about 2.1-2.2 volts.
The discharge voltage is about 2.0 volts and varies with temperature, discharge rate, charge
state, and age. The SLAB must be charged in a constant potential mode.
The lead-acid battery is the most widely used of the secondary battery types. Major
applications include automobiles, aircraft, aircraft support equipment, and various industrial
applications.
NICKEL-CADMIUM BATTERIES
The nickel-cadmium battery is a rechargeable system using alkaline electrolyte (a 31%
aqueous solution potassium hydroxide). Nickel-cadmium batteries, which may be vented or
sealed, have overcharge capability, high rate charge acceptance and nearly constant
discharge voltage. The disadvantages are the high initial and maintenance costs as well as the
cost to discard the battery at the end of life. The open circuit voltage of a fully charged cell is
about 1.35 volts. The discharge voltage is about 1.2 to 1.1 volts and varies with
temperature, discharge rate, charge state, and age.
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