Handbook on Lead Acid Cell for Railway signaling

8/14/2019 Handbook on Lead Acid Cell for Railway signaling

1/32

CAMTECH/S/2005/LAC/2.0 1

LEAD ACID CELL

1. Introduction

Two different types of lead acid cells are

manufactured by the industry and depending on

the application, these are normally referred to as

mobile or stationary. These are also called

Accumulators or storage cells.

This document includes instructions, which are

applicable for the installation and maintenance

of stationary secondary lead acid cells or

batteries.

2. Parts of Lead Acid Cell

Parts of Lead acid cell are shown in figurebelow.

Figure - 1

Lead Acid Cell March2005

Ver 2.0

1. Level indicator

2. Vent plug

3. Terminal ports

4. Cover

5. Separator guard

6. Positive plate7. Separator

8. Negative plate

9. Container

10. Plate rest


2/32


Level indicator and Vent plug.

For all capacities of lead acid cell vent/float plug

shall be of threads M27x3 pitch is provided. The

dimension of vent cum float guide plug are shown in

figure below:

Red mark

Green mark

Plug

Threads(M27x3 Pitch)

Transparent

Indicator

Float at greenmark level

mark levelFloat at red

Figure - 2


Ver 2.0


3/32


Plastic Skirtingof suitablecolour fireretardant

Microporous body

Plug

Suitable anti splasharrangement for

eelctrolyte so thatgasses can pass

Threads M 27x3 pitch

Body

25x10 approx8 windows of size

Figure 3


Ver 2.0


4/32


6 or 8 holes 0 2

for releasing gas

Figure - 4


Ver 2.0


5/32


Plates

The plates, which are actual electrodes, are:

Spongy Lead

Lead Peroxide

The plates will usually be plante or faure types.

In the plante type the plates are solid type and of

wed construction. Where as, in faure type a plategrid of antimony alloy is used with the lead peroxide

or spongy lead in a powdered from secured inside a

bay made of this grid.

Separators

The separators act as insulating piecesbetween the different plates.

separators are made of either specially

treated wood, perforated rubber, celluloid or

rubber fabric made porous by thick cotton

threads or glass wool.

The common separator is wood, since it

is the cheapest of all separators.

Container

The container is made of vulcanised

rubber, pitch celluloid or glass.


Ver 2.0


6/32


Celluloid or glass containers are

normally used for light duty work and celluloid

container for portable work.

Plate rest

The plate rest or bottom blocks are raised

ribs either fitted in the bottom of the jar or made

in the jar itself so that the plates do not touch the

bottom and the tope portion is kept at the correctlevel.

These also form a receptacle to collect

the sludge formed during its period of active life.

Terminal ports

All the positive plates are welded to one

bar and all the negative plates to another

common bar.

There is always one more negative plate

then the positive to provide equal working area,

on all sides of the positive plates.

The outside plates are, therefore, always

negative plates.

The terminal posts are upward extensionsof connecting bars. This forms the terminal post

and passes through the cover to enable external

connections to be made.

Cover

The covers are generally of vulcanized

rubber or pitch.


Ver 2.0


7/32


A hole is provided for pouring the

electrolyte and this can be closed by a screwed

cap. The cap is provided with minute holes

for gases to escape.

This is also known as Vent Cap

3. Brief description and working

A lead acid battery consists of positive and

negative electrodes immersed in an electrolytekept in sealed container. The material of the

positive electrode is lead dioxide (PbO2) and

that the negative electrode is spongy lead (Pb).

These electrode are electrically insulated from

each other using separators. The electrolyte is a

suitable mixture of sulfuric acid and distilled

water.

When the battery is fully charged, the negativeelectrode remains as Lead, the positive electrode

as lead dioxide and the concentration of sulfuric

acid solution (specific gravity is between 1200-

1220).

As the battery discharges, the positive and

negative electrodes convert chemically in to lead

sulfate. The chemical reaction consumes the acidand finally releases water in the electrolyte

solution, thereby reducing the specific gravity.

Capacity V/S Discharge rate


Ver 2.0


8/32


The capacity of the battery is the amount of

electricity that can be obtained from it. It can be

rated in two ways.

Ampere-hour rating

Watt-hour rating.

The ampere-hour rating is always given with the

specified discharge rate, that is.

a) 100 AH at 10 A rate

b) 150 AH at 15 A rate.

In(a)the maximum discharge current should not

exceed 10 Amps, and the period of discharge at this

rate is 10 hours.

Similarly, for (b) maximum rate is 15 Amps and

period is 10 hours.

This is also sometimes expressed as hour rate for

example 100 Amps. @ 5 hours rate worked, mean

that the maximum discharge current is 20 Amps.

and the period of discharge is 5 hours. The capacity

always reduces with increase in discharge rate so

that the actual ampere-hour capacity obtained is

usually 80 to 90% of the rated value.

Efficiency of a secondary cell

The efficiency of a secondary cell is

defined as the ratio of output of a cell to the

input required to restore the initial state of


Ver 2.0


9/32


charge under specified conditions of

temperature, current rate and final voltage.

Generally the efficiency is expressed inthree ways:

Ampere-hour efficiency.

Volt efficiency.

Watt-hour efficiency.

Ampere-hour efficiency is the ratio of the

ampere hours output to the ampere hours of therecharge.

The ampere-hour loss, which determines

ampere hour efficiency during cycle of charge

and discharge is principally that due to gassing.

Local action is responsible of certain

amount, but unless the test is spread over a long

period of time or the battery is in a veryunhealthy condition this loss may be

disregarded. Since gassing is due to charging

current in excess of the utilised in charging the

active material, ampere hour efficiency can be

increased by controlling the charging current to

keep it below the value, which will produce

excessive gassing, but such careful control of the

charging rate, and especially if the cycle ofcharge and discharge did not involve bringing

the battery to an absolutely fully charged

condition, an ampere hour efficiency of nearly

100% can be obtained.

Under commercial service conditions

including frequent cycles of charge and

discharge involving nearly the full capacity of


Ver 2.0


10/32


the battery, an ampere hour efficiency between

85 to 90% may be obtained.

4. Unpacking and storing

Carefully unpack the cells received from trade

(rough handling could damage them) and check

all the components including the vent plugs, vent

cum float guide, inter cell connectors, nuts and

bolts.

Inspect the sides and the bottom of the batterypacking case for any wet spots, which indicate

broken jars/containers. These might have been

broken during handling and transportation.

Cracked and broken batteries may be rejected

and details may be brought to the notice of the

supplier for replacement.

The battery must be stored in clean, cool and dry

room protected from sun, rain and dust.

5. Location and Installation

Mount the batteries in well-ventilated, clean and

dry rooms.

For small battery installations, natural

ventilation through windows and doors maynormally be sufficient. However, for larger

battery installation (more than 12 cells). Forced

ventilation methods using exhaust fans must be

provided.

Separate battery room are necessary to avoid the

adverse effect of fumes on other interlocking

and power equipment as well as to provide free


Ver 2.0


11/32


access to the maintenance staff (battery rooms

are not double locked.).

The battery room shall be provided with acidproof flooring and acid proof tiles on walls up to

suitable height.

Wherever, batteries are kept in field inside the

location boxes, suitable openings/holes are

necessary for ventilation.

Where batteries are housed in location boxes,

these housings shall be painted with acidresistant paint.

In some applications, where a few cells are

required to be kept in offices, equipment rooms,

residence etc. they may be housed in wooden

boxes proved with enough holes for ventilation.

Locate the batteries away from direct Sunrays

and heat emitting system.

Place the batteries on rugged wooden racks of

sufficient height so that it is possible to inspect

and maintain them properly.

Two or more coats of acid resistant paint of

approved type shall protect the racks.

The racks shall be level and mounted on

approved type of insulators.

A typical arrangement is shown in figure below.


Ver 2.0


12/32


Connector

Insulator

Connector

Centre of cells

Connector

+ + -

SINGLE/DOUBLE ROW SINGLETIER WOOD ON RACK

Figure - 5

InsulatorConnector

Connector Connector

SINGLE/DOUBLE ROW DOUBLETIER WOOD ON RACK

Centre of Cells

+ - +

Figure - 6


Ver 2.0


13/32


Lead acid cells of an approved type shall be used

and shall conform to specification no. IRS: S

88/93 for low maintenance lead acid cells. The cells shall be installed as per approved

drawings.

At the time of installation, capacity test shall be

done and record shall be maintained.

Insulate the cells from the floor and from each

other using insulators. Place wooden planks

under the batteries wherever the cells are kept onmasonry racks and floors, metallic frames and

location boxes.

Keep the individual batteries properly aligned

and leveled to avoid stresses on the

connectors/cable. Keeping battery insulator

block under the battery is desirable.

Ensure proper clearance between adjacent cells

for connecting the battery terminal connectors

and between adjacent rows from the angle of

maintenance.

Wooden battery racks must be protected against

decay by painting them using acid resistance

paint (Type 2 of IS 158-68).

On receipt of charged secondary cells, the vent

plugs shall be removed and the height of theelectrolyte shall be noted, if it is below the

prescribed level, the loss may be due to spillage

during transit. The level of the electrolyte can be

restored by adding battery grade acid of

recommended specific gravity.

6. Initial Charging


Ver 2.0


14/32


Unless, good facilities are available in the Chief

Signal/Telecom Inspectors depot for chargingsecondary lead acid cells and their subsequent

handling and transportation to actual site of

installation it is advisable to do the initial

charging at site.

Initial charging of the batteries shall be done as

per instructions of the manufacturer and the date

of charging shall be suitable painted on thebatteries, or on a separate board kept near the

batteries.

The procedure given below, however, generally

applies for initial charging to all makes of lead

acid batteries.

Ensure that all the cells in the battery set are of

the same type and capacity. Charging individual

cells separately is not advisable.

Battery grade dilute sulfuric acid conforming to

IS 266 and distilled or de-mineralized water

conforming to IS 1069 shall only be used as

electrolyte

A glass, porcelain, rubber or any other acid

proof container shall only be used for mixing

acid and water. Always acid shall be added to water.

During mixing, the solution must be stirred

constantly so that its temperature does not

exceed 50 C.

Ratio in which sulfuric acid and distilled water

must be mixed is given in the table 1.


Ver 2.0


15/32


Specific

Gravityof the

original

Acid

Specific

Gravityof the

solution

required

Distillwater

Sulfuricacid

1825 1400 11 7

1825 1190 5 1

1400 1190 6 5

Table-1

While preparing electrolyte, the solution should

be continuously stirred using a glass or wooden

rod.

The temperature of the same should not be

allowed to exceeds the limit, then allow it to

cool.

Allow it to cool for at least 10 to 12 hours and

see that the specific gravity is between 1190 and

1200.

Since, specific gravity varies with the

temperature a correction must be applied to

arrive at the correct value.

For temperature > 27 C 0.0007 per CFor temperature < 27 C -0.0007 per C

Clean all the new cells for the battery set with

distilled water and fill all of them with this

electrolyte which will ensure uniform specific

gravity.


Ver 2.0


16/32


The level of the electrolyte should be about 12 to

15 mm above the plate.

Check either the red mark indicated on the ventfloat or use a glass tube to see the level.

The charger output terminals must be correctly

connected to the battery set i.e. + to + and to -.

Ensure that all electrical connections between

the charger and the battery are tight and offer

good conductivity.

Apply charge for 35 hours at the starting currentrate given by the empirical formula/ thumb rule,

where the starting charging current is taken as

4% of the ampere hours (AH) value of the cells.

Starting Current = 0.04 x AH value

(For initial charging)

Check specific gravity and voltage reading every

8 hours. Apply temperature correction on thespecific gravity readings.

Stop charging when the specific gravity becomes

12105.

If the specific gravity of the cell/cells after

charging does not improve to its normal value, a

small quantity of electrolyte is taken out and

replaced by solution of higher specific gravity

(1400). A fresh charging cycle must then begiven for two hours to ensure mixing.

Discharge the battery through a suitable load

(lamps) till the specific gravity reduces to

between 1180 and 1190 and the voltage of cells

to 1.85 V.


Ver 2.0


17/32


Repeat the cycle of charge and discharge once

again and then charge finally for use.

Ensure that the battery is charged optimally andno over charging, over gassing or heating takes

place.

Apply a coat of petroleum jelly or non-oxidizing

grease on the battery connectors to avoid

corrosion.

Close all the vent caps and ensure that the floats

are in position. If after charging, the battery are not put up in use

for 15 days they should be given as equalizing

charge to bring specific gravity of all the cells to

12105.


Ver 2.0


18/32


7. Maintenance and Inspection

Maintenance tests and repair work on the cell,which may interfere with safe operation of

trains, shall not be started until movements are

fully protected.

Temporary repairs or adjustments shall be made

in such a manner that safety of train operation is

not impaired when repairs and or adjustments

are made. After the maintenance and repair work

(Including temporary repair) are completed tests

shall be immediately carried out to ensure that

the connected apparatus functions satisfactorily.

Battery charger used shall be as per specification

no. IRS: S 86/2000 for battery charger self

regulating.

Float and boost mode shall be adjusted to 2.15Volt/cell and 2.4 Volt/cell

The battery room and location boxes shall be

kept well ventilated, free from water, oil or dust

surroundings and batteries shall be kept clean.

Connecting cables shall be flexible and

sufficiently long to prevent strain on the battery

terminals.

The electrical connection shall always be kept

tight.

The terminals and connections shall be coated

with pure Vaseline or petroleum jelly to prevent

corrosion.

Grease shall not be used.


Ver 2.0


19/32


The electrolyte shall be maintained at the correct

level by topping up as often as necessary with

distilled or demineralised water. Electrolyte lost due to spillage shall be replaced

with proper amount of electrolyte of the same

specific gravity as that of other cells of the

battery.

Electrolyte shall not be added in any other

circumstances.

Each cell shall be tested periodically and itscleaning and charging arranged so that its

voltage and specific gravity are within specified

limits.

Test results and dates of cleaning and charging

adjustments shall be recorded on the Battery

History Card.

A separate card shall be maintained for each

battery set. The voltage of individual cell shall not fall

below 1.85 Volts.

7.1 Precautions

Checks / tests on battery and general cleaning

normally do not affect the circuit it is feeding.

However, care must be taken to ensure that the

working circuits do not get affected.

For maintenance and repair works (including

temporary repairs) which may require

disconnecting or recharging or replacement of

the battery, disconnection notice must be issued

to the ASM on duty and work commenced after


Ver 2.0


20/32


the same is allowed and necessary precautions

have been taken. This will ensure safety in train

operation. Always use suitable goggles and rubber gloves

and wears an apron while working with battery

electrolyte.

7.2 General Cleaning

Check each cell of the battery set once everyfifteen days. Ensure that all connections are

tight. Remove dust or dirt from the battery top

and connections. Wipe the battery using a wet

cloth piece and allow it to dry.

At least once in three months, neutralize the acid

on the battery covers and terminals with either

ammonia or sodium bicarbonate solution in

water before cleaning. Keep terminals and metalparts free of corrosion.

7.3 Electrolyte

Distilled water (IS 1069) should be used to top

up the cells at regular intervals to maintain the

recommended electrolyte level. The level goesdown on account of evaporation, the electrolyte

level should never drop below the top of the

plates.

Do not let it spill out to avoid electrolyte loss

and corrosion. Add distilled water only when the

battery is charging or gassing.


Ver 2.0


21/32


Electrolyte lost due to spillage should be

replaced with proper amount of electrolyte of the

same specific gravity as that of other cells of the battery. Under no other circumstances should

electrolyte be added.

7.4 Voltage and Specific Gravity.

The specific gravity and the terminal voltage of

batteries should be checked.

Measurements must be taken after switchingOFF the charger of at least one hour.

It is a good practice to switch off the charger of

at least one or two battery sets for 4 hours or

based on the battery set condition during

inspection and maintenance trips to the station.

This helps in not only accessing the condition of

the battery but also provides a discharge cycle. Keep accurate records of the battery voltages

and sp. gravity as these are extremely important.

They provide a detail history of the performance

of each cell. Variations observed from normal

values pin point the degradation in battery

condition which can be promptly corrected.

In case, in a particular battery set, the specific

gravity of individual cells are observed to bevarying considerably, the electrolyte must be

exchanged / balanced between cells with higher

value of specific gravity for those having lower

value. This will also ensure uniform gravity in

all of them. Balancing of electrolyte has to be


Ver 2.0


22/32


done for individual cell after taking out from the

set.

Records must include in the following proforma.

Form - S&T/BCP

______Railway______Division

Station_________

Signal and Telecommunication Department

SECONDARY BATTERY HISTORY CARDNo. of Cells: Installation date:

Capacity (AH): Circuit reference:

Battery Set no.: Charging current:

Battery set voltage: Charger make:

Battery make : Charger capacity:

Cell no.

Workdon

eand

remarks

Signature

Date

Param

eter

1 2 - 10 - 15

Specific

gravity

Cell

voltage

Specific

gravity1220

Cell volts


Ver 2.0


23/32


When the charge in the battery set has gone down

considerably, recharging must be done at a

current equal to 10% of the AH value until thespecific gravity of the cell came to 12105.

7.5 Cable and connections

Connectors and connecting cable should be

flexible and sufficiently long to prevent strain on

the battery terminals. The connecting cablesshould have lead coated eyelets/lugs for

connections.

Electrical connection should always be kept

tight. Loose connections get heated up leading to

failure.

Terminals and connections should be coated

with pure Vaseline or petroleum jelly or non

oxidizing grease to prevent corrosion. Ifcorrosion occurred, it should be removed by

wiping clean with a solution of washing soda

and water (or dilute ammonia) taking care that

the solution does not enter the cells.

Grease shall not be used.

7.6 Equalizing charge

The battery, which is continuously used in Float

Service should be given equlising charge to

compensate for low/ uneven specific gravity of

cells. Equilsing charge is given to cells once in a

three months at fixed current (normally 1/10 th of

AH capacity). The charging should be continued


Ver 2.0


24/32


till the voltage and specific gravity in all cell

have remains constant for three consecutive half

hourly readings.

7.7 Miscellaneous

The vent plugs should be kept in position and

tight. If a vent plug is lost, it should be replaced

early to prevent spillage of electrolyte.

Defective cells should be disconnected andreplaced. Batteries showing irregularities, which

can not be corrected, should be taken out of

service and report made to proper authority.

Only approved hydrometer and voltmeter should

be used for recording observations. It is

recommended that :

Voltmeter should be of an accuracy class

not inferior to 1.0 in accordance withIS:1248-68. The resistance of the voltmeter

must be at least 1000 Ohms per Volt.

7.8 Periodicity

The periodicity of maintenance, will generally

be as given below, except otherwise modified bythe concerned Railway.

Maintainer Period

ESM/WTM Weekly

JE/SE Monthly

SSE Every quarter


Ver 2.0


25/32


8. Trouble shooting

Sr. Cause Remedy

1. Battery does not charge.

1.1 Disconnection in the

charging circuit.

Check the circuit

and rectify.

1.2 Blowing OFF of charger fuse

AC or DC side

Check the fuse

and rectify

1.3 Loose connections or highresistance at terminals

Check theconnection, clean

and tighten them.

1.4 Defective charger not

feeding current

Replace the

charger

1.5 Wrong connections Check the

connections and

rectify

2. Battery takes more time to charge2.1 Loose connection or higher

resistance at terminals

Open the

connections and

clean and the

reconnect

2.2 Charger not able to feed

enough charging current

Replace the

charger

2.3 Excessive discharge Charge thebattery separately

2.4 Wrong connection Check the

connection and

rectify.

2.5 The charger out put Voltage Adjust the


Ver 2.0


26/32


Sr. Cause Remedy

may be less than 2.5 Volt percell.

charger outputvoltage.

2.6 Number of cells use may be

more than the charger

capacity.

Adjust number of

cells as per 2.15

volt per cell

3. Battery does not last for long

3.1 Low electrolyte level Maintain the

level properly3.2 Uneven specific gravity and

voltage of the cells

Equalize the

specific gravity

of each cell with

the electrolyte

3.3 Not properly or full charge Recharge again

3.4 Leakage in some cells Replace them

3.5 Reverse polarity on some

cells

Remove the

reverse polaritycell from the set.

3.6 Inadequate number of cells

or load current is more.

Installed the cells

as per the load

3.7 Low specific gravity Add the solution

of higher specific

gravity.

3.8 Charger output voltage orcharging current may not be

adequate

Adjust the outputvoltage and

charging current.

3.9 Batter charger may not be

adequate for charging battery

of given AH

Replace the

charger with

adequate capacity

4. Battery over heats during charge or discharge


Ver 2.0


27/32


Sr. Cause Remedy

4.1 Charging current very high,especially at the finish.

Make propercharging current

4.2 Charger voltage high. Check the voltage

and adjust

properly.

4.3 Charged for longer period. Discharge the

battery with

suitable load.4.4 Over discharged or excessive

load current

Adjust the load

current

4.5 Poor ventilation or

temperature is high

Make proper

ventilation

4.6 Internal short circuit Replace the

battery

4.7 More sediment material inthe cell, old/worn out cells

Replace the cell

4.8 Low level of electrolyte Add the distilled

water as per

requirement

5. Low electrolyte level

5.1 Broke/cracked container of

cell

Replace the cell.

5.2 Distilled water not recouped

regular.

Add the distilled

water as per

requirement

5.3 Excessive charging Adjust the

charger current

5.4 Excessive heat Provide


Ver 2.0


28/32


Sr. Cause Remedy

ventilation5.5 Vent caps missing Provide new vent

caps

6. Voltage and specific gravity of cells unequal

6.1 Internal short circuit or

leakage

Replaced the cell.

6.2 Leakage of electrolyte

through crack cell, sealingcompound and covers

Replaced the cell

6.3 Dirty terminals of cell top Clean the

terminals.

6.4 Used with low electrolyte

level

Use proper

electrolyte

6.5 Sedimentation high inside

the battery

Replace the

battery

6.6 Plates worn out Replace the

battery

6.7 Impure electrolyte Replace the

electrolyte and

recharge the

battery.

7. Specific gravity is higherthen normal during float

charging due to float voltage

is high.

Adjust floatvoltage.


Ver 2.0


29/32


9. Spare parts

The following spare parts and consumables willbe necessary.

Acid resistance paint IS158-68

Sulfuric acid IS-266

Distilled water IS-1069

Ammonia

Sodium bicarbonate (washing soda) Petroleum jelly or Vaseline or non-oxidizing

grease

Cloth for cleaning

Nuts and bolts

Connectors and cables

Cotton waste grade A

Vent cum float guide plugs Floats

Rubber gloves.

10. Tools and measuring equipment

Following tools and measuring equipment will

be necessary:

For measuring voltage, DC voltmeter ranges

0 volts to 200 volts

DC ammeter ranges 0 amps to 50 amps

Syringe type hydrometer

Crocodile clips

Wires or cables of adequate current capacity


Ver 2.0


30/32


Battery charger with controls for charging

current

Spanner set

Battery shunt meter

Thermometer C range 0-80C

Glass tube (20 to 30 cms long)

Glass or PVC or porcelain or rubber

container

Glass rod (30 to 40 cms long )

Nylon brush with tough bristles.

11. Dos and Donts

11.1 Dos

Ensure that the positive and negative wires are

connected to positive and negative terminalsrespectively, while connecting the charger to the

batteries.

If the batteries not in use, keep the battery in full

charge condition by given an equalizing charge

atleast once every month.

Ensure that the float indicator is available and in

working order.

Electrolyte is highly corrosive and should be

handled carefully to avoid injury to person or

damage to clothing or equipment. If the

electrolyte is accidentally spilled, it should be

flushed with plenty of water immediately, after

treating with washing soda solution.


Ver 2.0


31/32


After the failure of power supply battery should

be charged on boost mode i.e. load plus three

ampere, preventing the battery from buckling of battery due to rising temperature and

evaporation of distilled water.

Ensure that charger float and boost voltages has

been adjusted to 2.15 Volt per cell and 2.4 Volt

per cell respectively.

Ensure that charger is suitable for charging the

AH capacity of battery used.

11.2 Donts

Do not allow over charging, excessive gassing

and heating

Do not allow the batteries to get fully discharge.

Do not allow open flame smoking near the

batteries to eliminate danger from explosion or

fire.

Extreme care must be exercised to avoid a spark

or flash when changing connections or working

on or near the battery.

Battery lead should first be disconnected at a

point remote from the battery set.

Metal jugs should not be used for carrying waterrequired for topping up.

Do not miss handle the cells, specially during

transportation.

Do not hold the cells by the electrode terminals.


Ver 2.0


32/32


Handbook on Lead Acid Cell for Railway signaling

Documents

Transcript of Handbook on Lead Acid Cell for Railway signaling