1. Caring for and testing of batteries
G.KUMARAN
A.D.S.T.E/BPA

2. BATTERY
 Group of connected cells forms BATTERY.
 Classification of CELLS
 Primary Cells: The chemical materials are used up
as electric energy is produced. It is discarded when
its active material is depleted and it no longer
produces electrical energy.
 Secondary Cells: A reversible chemical reaction is
used to separate charges so that the cell can be
returned to its original chemical state many times

3. Railway Signalling Applications
 In Railway Signalling Applications Secondary Cells are
usually used for situation requiring larger amount of
energy at high currents.
 In Railway Signalling Application three types of lead
acid cells are used
 Flooded type Lead Acid Cells IS-1651 (not used)
 Flooded type low maintenance Lead Acid Cells IRS-S88/93.
 Sealed Lead Acid Cells S93/96(For signaling applications
these cells are not used)

4. Flooded type low maintenance
Lead Acid Cells IRS-S88/93.
 At present in Railway Signalling Applications Flooded
type low maintenance Lead Acid Cells are used.
 Advantage of LMLA over Lead Acid Cells.
 In Grid Alloy composition Low percentage 2% of
antimony is used. This reduces the need for adding
water since very little is boiled of during charging.
 Ampere-Hour efficiency more than 95%.
 High Watt-Hour efficiency more than 80%.

5. Construction details of LMLA
 In LMLA number of positive and negative plates
are interleaved and separated by porus rubber
sheet. This layering provides greater surface area
and current availability. All the positive plates are
electrically connected as are all the negative
plates. This connections yield a parallel (Higher
current) parallel arrangement for single cell
developing approximately two volts.

7. Principle of Cell working
 When two electrodes of dissimilar metals are placed in
an electrolyte there will be miserable potential
difference at their terminals. In the Lead Acid System
one electrode of lead peroxide and another of pure
sponge Lead or immersed in the electrolyte.
 Positive plate is made of Lead Peroxide, Negative plate
is made of Sponge Lead
 Electrolyte is H2SO4.
 This above combination in the cell produces about
two volts.

8. CHEMICAL REACTION
 Discharge.
In the discharged state both the positive and negative plates become
lead(II) sulfate (PbSO4) and the electrolyte loses much of its dissolved
sulfuric acid and becomes primarily water. The discharge process is
driven by the conduction of electrons from the positive plate back into
the cell at the negative plate.
 Charge.
In the charged state, each cell contains negative plates of elemental
lead (Pb) and positive plates of lead(IV) oxide (PbO2) in an electrolyte
of approximately 33.5% v/v (4.2 Molar) sulfuric acid (H2SO4). The
charging process is driven by the forcible removal of electrons from the
negative plate and the forcible introduction of them to the positive
plate.
DISCHARGE
Pb+PbO2+2H2SO4 2PbSO4 + 2H2O+ Electrical Energy
CHARGE

9. 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

10. Ampere-Hour Capacity.
 A batteries current rating is usually given in units of
Ampere-Hour Capacity, based on 10hour discharge
period. During that period, the cells output voltage
must not drop below 1.8V for example 80 AH battery
should deliver 8A current for 10Hours without any cell
dropping below 1.8V. It is unlikely, however, that the
battery could actually deliver 80 Amps per one hours-
cells are less efficient at higher discharge currents. In
signalling applications the various capacity of batteries
are used, 40 AH, 80AH, 120AH, 200AH, 300AH etc.,

11. Initial Charging.
 In the absence of manufacturer’s instructions the following
method shall be followed.
 Mix one par of 1.840 Specific Gravity acid with five parts of
distilled water. Never pour water into acid. The acid
explodes and spills over and causes injuries. Always add
acid to water for diluting.
 Allow the acid to cool down.
 Pour the cool acid into the cell up to the float mark.
 Allow the cells to cool down for not less than 12 hours and
not more than 24 hours.
 Before putting the cells on first charge top up the acid to
proper level if there is fall in the level.
 Charge the cell at 20-Hr. charge rate for 80 hours.

12.  During the charging the cell temperature shall not rise above 50
degree C. If it rises, discontinue charging until the temp. comes
down to about 40 degrees. If the temperature crosses 45 degree
C, reduce the charging rate to half.
 However, the total charge input should be equal to 80hrs X I,
where I=20 Hr. charging rate.
 While charging, there will be fall in the level of electrolyte due
to loss of water by gassing. Restore this at intervals at intervals
of say 24 hours by adding required quantity of distilled water.
 At the end of charging, the specific gravity of the electrolyte is to
be adjusted to 1,200±0.005 at 27 degree C. If the specific gravity
at the end of charging is above 1.200 add distilled water and if it
is below 1.200 and 1.400 specific gravity acid and charge for a
couple hours and check the gravity again.
 Allow the cells to cool down.
 Discharge the cells at one tenth of AH capacity to an end voltage
of 1.85V per cell.

13.  After fully charged cells should not be kept
unused. If the cells are continued to keep in
ideal condition the cell capacity
automatically looses,
Due to the following reasons.
 Thin layer of Lead Sulphate formed on
plates makes the cell plates ineffective.
 Stratification of acid leads to higher
specific gravity acid reaching the bottom
of the cells.

14. Cells Connectivity
Series: Parallel:
Connect the positive terminal Connect all the positive wires
of one cell into negative of the cells to a single wire
terminal of the other cell and Connect all the negative wires
so on…. of the cells to a single wires.
Then you will get a battery
V=E1+E2+E3
voltage of a single cell. But the
I = Current flowing in one current will be total of all
direction cells.
Total EMF = some of the EMF I= I1+I2+I3 and V= V1=V2=V3
of each cells

15. Battery Maintenance
 Freshening Charge
 After Initial Charging of Cells if the batteries are not
connected to circuit, the freshening charge rate is 4% of
the full capacity to be done (1.6Amps for 40AH).
 During the maintenance of batteries if one of the cell
found low specific gravity/ low terminal voltage
compared to others, the particular sick cell to be
removed from bank and should be boost charged until
the cell regains its capacity. At any circumstances
adding of acid or higher specific gravity electrolyte
should not be added.

16.  Negative polarity :- During the course of battery
maintenance if the cell is accepting less charge than
other cell in the bank, over a period of time the cell
slowly loses its capacity and assumes negative voltage
if discharged. This negative polarity cell will
disconnect the battery voltage to load such cells
should be removed from the battery bank and it
should be charged separately.
 Why Acid cannot be added to working Cell?
The specific gravity of the cell is measure of state of
charge of cell. Addition of acid changes the specific
gravity without change in the state of charge of cell.
Addition of acid of higher specific gravity does not
remove the Lead sulphate layer on the cell plates.
Only the charging current breaks the sulphate layer.

17. Equalisation Charge
 A battery bank requires equilasation charge periodically.
Normally once in 3 months.
 Why and When Equalisation charge is required?
 The individual cells of battery are not identical some cells
may not be fully charged when the charging process is
completed. During the course of measuring the voltage of
each individual cell while the battery is at rest a variation of
0.05V between cells indicates imbalance same way if the
variation of 20 points in the specific gravity between cells also
indicates imbalance in battery bank.
 Both the conditions can be corrected by equalisation charge.
Equalising Charge rate 1/10th of AH Capacity of Cell.

18. Types of Charging
 Auto mode of Charging: Depending on the
condition of Cell the charger selects float or boost
charging in Auto mode when the maximum charging
current falls below 5% the charger goes to float mode.
 Float Charge : Charging the cell to reach ultimate
terminal voltage of 2.15V. Maximum charging current
is limited to 10 hours discharge rate
 Boost Charge : Charging the cell to reach ultimate
terminal voltage of 2.4V. Maximum charging current
is limited to 10 hours discharge rate.

19. Topping of Distilled Water
 During battery maintenance if the electrolyte level
found low distilled water should be topped, at any
circumstance normal drinking water should not be
added to the cell.
 If We Add?
Normal drinking water even though clear of gems
still have impurities like copper and iron etc., During
discharge the plates are covered by copper and iron
sulphate which cannot be broken by charging current.
It causes permanent damage to the cell and reduces its
capacity.

20. Over Charging/Discharging of Cells
 Over Charging:
 The cells start gassing and water is lost – distilled water is
required to be added more frequently
 The temperature raises some time may damage the cell and
also it leads to corrosion of positive grid.
 Over Discharge:
 If a cell is discharged at a higher current rate then
recommended the cell plates are likely to be damaged
permanently means if we discharge a cell beyond its capacity
the cell may not be revived by charging it again.
 Both the Cases the cell becomes useless.

21. Capacity Test
 During the maintenance, capacity test to be done on
battery bank once in a year.
 Capacity of Battery in AH= Load Current in Amps x No. of
Hours
for eg:- Load Current=5A, original capacity of cell 40AH
Time taken for voltage of any cell to fall to 1.8V=4 hrs
Capacity in AH= 5A x 4 hrs
= 20AH
when the capacity of the battery falls to 50% of the rated
capacity it should be planed for replacement. This type of
test is also call as Curative Discharge.

22. Maintenance Tips
 Clean the terminals of Sulphation, if required apply a
very thin layer of petroleum jelly.
 Maximum depth of discharge permitted is 80%.
However for the purpose of design 50% DOD is
considered.
 All the battery terminals should be tightened during
charger ON condition.
 Proper cross section cable should be used between
charger to battery. For example, 16sqmm copper cable
should be used for 200AH batteries.

23.  Battery connecting strap, bolts and nuts should be
used as per OEM.
 Connecting cable between cell and chargers should be
provided with proper size of copper lugs.