Fundamental Electronics

1. BACK UP SYSTEMS
CHAPTER 16.1
BATTERIES AND CELLS
By
Dinesh Kumar Sarda

2. WHO INVENETD BATTERY ??
Alessandro Volta was an Italian
physicist, chemist, and a pioneer of
electricity and power, who is
credited as the inventor of the
electrical battery
Mr.Volta demonstrated in 1791 that
when two metals and brine(salt
solution)-soaked cloth or cardboard
are arranged in a circuit they
produce an electric current.

3. WHAT IS A CELL??
A chemical cell is defined
as a device that generates
electricity by converting
chemical energy to
electrical energy.

4. A cell is a unit which includes
two different electrodes
1. Cathode
2. Anode
separated by separators
immersed in an electrolyte in
a suitable container having
terminals coming out of
electrodes for connecting to
external circuit.
DRY TYPE
WET TYPE

5. BATTERY VS CELL
Strictly, one
battery is a CELL,
and a group of
cells connected
together is
called a
BATTERY.
CELL
BATTERY

6. TYPES OF BATTERY
Primary Batteries
AND
Secondary Batteries

7. PRIMARY BATTERY
 CHEMICAL PROCESS NOT REVERSABLE
 CHEMICAL REACTION TOTALLY DESTROY ONE OF
THE METAL AFTER A PERIOD OF TIME .
 In simple terms it cannot be recharged and reused
again and again.
 Even if never taken out of the original package,
disposable (or "primary") batteries can lose 8 to 20
percent of their original charge every year at a
temperature of about 20°–30°C
 EX: ZINC CARBON (1.5V), ALKALINE (1.5V)

8. SECONDARY BATTERIES
 CAN BE RECHARGED
 CHEMICAL REACTION REVERSIBLE
 THE ELECTRODE & ACID MIXTURE CHANGE AS THE
BATTERY SUPPLIES .THIS IS CALLED DISCHARGING.BY
APPLYING CURRENT TO CELL IN OPPOSITE
DIRECTION,THE BATTERY MATERIAL RESTORED.THIS IS
CALLED CHARGING
 Rechargeable batteries self-discharge more rapidly
than disposable alkaline batteries, especially nickel-
based batteries; a freshly charged NiCd loses 10% of its
charge in the first 24 hours, and thereafter discharges at
a rate of about 10% a month
 EX: LEAD ACID(2.0V),NICKEL-CADMIUM(1.2V),NICKEL-
METAL HYDRIDE(1.2V), LITHIUM ION(3.3V)

9. DRY CELL VS WET CELL
The basic difference between the two is the nature of
electrolyte used.
DRY CELL: Has a moist paste rather than a conducting
liquid and is more easily transportable.
WET CELL: Has a conducting liquid rather than a paste
and is difficult to transport.

10. LEAD ACID BATTERY
Invented in 19th
Century.
Rechargeable Applications
Widely used in various industries,
generation plants, hotels ,hospitals,
,power backup in home.
Automobile
Industries
Best selling battery
and most frequently
used in automobiles.
Powers the wipers
headlight,radio,air
conditioning & most
importantly the engine
starter.
Electrochemistry.mp4

11. BATTERY CONSTRUCTION

12. 1. BATTERY CASE & COVER:- The battery case and cover ...
 form a sealed container
 Protects the internal parts
 Keep the internal parts in proper alignment
 Prevent the electrolyte leakage
 is made of polypropylene, hard rubber, and plastic base materials.

13. 2. PLATES:-Two plates:
1. POSITIVE PLATE- It is made of antimony covered with an
active layer of lead dioxide(brown coloured).
2. NEGATIVE PLATE- It is made of lead covered with an active
layer of spongy lead.

14. 3. SEPERATOR:- Plates are separated by thin porous separator (woven glass or
plastic envelope).They allow electrolyte to pass freely between
the plates but prevent the plates from touching each other.
4. CELLS:- A typical lead acid battery is organized into cells. Each cells....
 consist of multiple positive and negative plates immersed in their own
electrolyte reservoir.
 produce about 2.1 volt regardless of battery size.
 are connected in series with heavy internal straps.

15. 5. VENTING SYSTEM:- They allow controlled release of hydrogen gas which forms
normally during battery recharging. If removed ,they permit
checking electrolyte and if necessary adding water.
6. ELECTROLYTE:
 It is mixture of Sulphuric acid (36%) and Water (64%).
 It reacts chemically with the active material on the plate to produce voltage (electric
pressure).
 SPECIFIC GRAVITY OF ELECTROLYTE:-
 When fully charged specific gravity of battery
electrolyte is 1.270
 Specific gravity is measured by Hydrometer
or Refractometer.
 SULPHATION:
 Sulphation starts when specific gravity falls below 1.225 or voltage measure less
than 12 volt.
 Sulphation destroy the battery ability to generate volts and amps.

16. WORKING OF LEAD ACID BATTERY
There are four stages of working:
1. CHARGED: A fully charged battery contains....
• Negative plate of spongy lead
• Positive plate of lead oxide
• Electrolyte consisting of 36% acid & 64% water.
2. DISCHARGING: During discharging...
• Electrolyte becomes diluted and plates becomes sulphated.
• Electrolyte divides into hydrogen and sulphate.
• The hydrogen combines with oxygen from the
positive plate to form more water.
• The sulphate combines with the lead in both plates
to form lead sulphate.
3. DISCHARGED: In a fully discharged battery, both
plates are covered with lead sulphate and the
electrolyte is diluted to mostly water
4. CHARGING: During charging...
• Sulphate leaves the plates and combines with hydrogen to
become sulphuric acid.
• Free oxygen combines with lead on the positive plate to
form lead dioxide.

17. ELECTROCHEMICAL REACTION

18. Specific Gravity
 The State of Charge of Lead Acid Cell can be checked by
determining the specific gravity of the electrolyte.
 Specific gravity is a ratio of the weight of the given volume of the
Electrolyte to the same volume of the water at temperature 68
degree F, a fully charged cell should have specific gravity of 1.200,
a fully discharged cell 1.800 both figures are related to the specific
gravity of water which is 1.00 the specific gravity can be measured
with hydrometer.
 Why the Specific gravity of LMLA cells kept at 1200-1220?
 If the specific gravity of Acid less than 1200 there the
internal resistance is too high.
 If the specific gravity is too high the acid damages the
positive and negative plate materials and reduces the cell
life hence the specific gravity is in the range of 1200 to
1220. This is specified by different manufactures
How to check specific gravity sing hydrometer. ✔.mp4

19. BUTTON TYPE CELL
Button cells, also known as coin cells, offer
small size and ease of stacking but do not
allow fast charging. Most commercial button
cells are non-rechargeable

20. CELL CONNECTIVITY
Cells can be connected in either
series or parallel

21. SERIES CONNECTION
• Connect the positive terminal of one cell into
negative terminal of the other cell and so
on….
• V=E1+E2+E3
• I = I1=I2=I3 (Current flows in one direction)
• Total EMF = SUM of the EMF of each cells

22. PARALLEL CONNECTION
• Connect all the positive wires of the cells to a
single wire
• Connect all the negative wires of the cells to a
single wires.
• Then you will get a battery voltage of a single
cell. But the current will be total of all cells.
• I= I1+I2+I3 and V= V1=V2=V3