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Batteries
• Battery Principles
• Battery Types
• Battery System
1
Batteries
Batteries are
collections of cells
that produce
electricity through
electrochemical
reactions. Cells can
be configured into
batteries of many
different shapes and
sizes.
2
Battery Design
Many components are
common to various
battery designs.
3
Battery Capacity
Higher temperatures
and slower discharge
rates result in
increased battery
capacity.
4
Discharging Reaction
Electrochemical reactions
within a cell produce a flow
of electrons from the
negative terminal to the
positive terminal.
5
Discharge Rate
Slower discharge
rates remove more
energy from a battery
than faster discharge
rates.
6
State of Charge vs. Depth of Discharge
The state of charge and
depth of discharge of a
battery always add up to
100%.
7
Average Daily Depth of Discharge
When arrays are used
to charge batteries,
seasonal isolation
variations affect depth
of discharge values.
8
Self-Discharge Rates
Lead-antimony designs
are vulnerable to high
self-discharge rates at
higher temperature.
9
Charging Reaction
The charging reaction
within a cell is the
reverse of the discharge
reaction.
10
Multiple-Stage Charging
Bulk, absorption, and float charging control battery
voltage with the charging current during a multiple
stage charging cycle.
11
Electrolyte Freezing Points
The freezing point of electrolyte changes at
various states of charge because of changes
in specific gravity.
12
Sulfation
Sulfation reduces the
capacity of a cell by
locking away active
material as crystals.
13
Stratification
Stratification results
when the specific
gravity of the
electrolyte is higher
at the bottom of a
cell than at the top.
14
Characteristics of Lead-Acid Batteries
The characteristics of lead-acid batteries vary
between different designs.
15
Two Types of Ni-Cd Batteries
Two types of Ni-Cd batteries have characteristics
suitable for PV systems.
16
Battery Selection Criteria
System requirements
and characteristics of
battery types must be
considered when
choosing a battery.
17
Batteries in Series
Connecting batteries in series increases
system voltage.
18
Batteries in Parallel
Connecting batteries in parallel increases
system capacity.
19
Batteries in Series and Parallel
Series and parallel connections can be combined
to produce a desired system voltage level and
capacity.
20