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What
is a battery?
A battery is an electricity storage
device which can be found in any number of shapes, sizes,
voltages and capacities.
When two conducting materials (often dissimilar metals) are
immersed in a solution, an electrical potential will exist
between them If connected together through a closed circuit,
a current will flow. The value of this potential (or voltage)
is dependent on the materials used, giving rise to a whole
family of battery types each having benefits and restrictions
in use. Examples are:- lead acid, nickel cadmium (Nicad),
lithium, silver alkaline.
This manual is concerned only with one battery technology
- the most successful - lead acid (lead and lead oxide immersed
in sulphuric acid). Each cell has a 2 volt potential.
A battery is simply a number of cells connected together with
a given voltage and capacity. The more cells the higher the
voltage, the larger the plates the higher the capacity (in
general).
Purely for convenience, batteries
are made in 12 volt blocks with 6 cells but are also available
in 6 volt, 4 volt and even 2 volt, single cell blocks.
Batteries can be connected in series to achieve whatever voltage
is required (add the number of 2 volt cells) and in parallel
to achieve the capacity required (add the capacities of each
parallel battery or string of batteries) For larger systems,
a number of series connected strings maybe connected in parallel
with each other. This achieves both a higher voltage and capacity
(see Choosing the correct size of battery).
The
lead-acid battery
There are two concepts in lead-acid batteries
1. Sealed or Valve Regulated Lead Acid VRLA
2. Open - Vented
There are three basic applications
1. Industrial
2. Automotive (starter i.e. cars, commercial vehicles)
3. Traction (electric motor drive i.e. milkfloat)
ALWAYS USE A BATTERY BEST DESIGNED
FOR THE APPLICATION.
This guide is focused on Industrial Standby applications and
NOT Automotive and Traction use.
Industrial
batteries
Industrial batteries are available from two distinct groups
with the following features. Note: VRLA have superseded open-vented
in many applications.
| OPEN-VENTED |
SEALED/VRLA |
Older
technology
|
Environmentally
friendly |
|
Require separate battery room |
Use
directly in office environment |
|
Regular routine maintenance |
Low
maintenance - 'Maintenance free' |
| Separate
safety requirements |
Self-contained.
Safe |
| Store/use
in vertical position |
Store/use
in any orientation |
| Can
require extensive cabling |
Can
be used internal or adjacent to load |
| VRLA
has in many instances replaced the open-vented type. |
Note - the term sealed lead-acid SLA is an old acronym considered
misleading and is now replaced by Valve Regulated Lead Acid
VRLA
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