BATTERIES

AbstractionRequirements of vehicle battery.

Choosing the correct battery.

Positioning the vehicle battery.

Lead acid batteries.

Battery Rating.

Maintenance.

Charging the lead acid battery.

Servicing the battery.

Safety.

Requirements of the vehicle batteryThe battery in a vehicle is used as the source of Energy for the vehicle when the

engine and the alternator are at rest position. The battery has a number of requirements, which are listed below broadly in order of importance.

To provide power storage and be able to supply it quick enough to ignite the vehicle’s engine.

To allow the use of parking lights for a reasonable time.

To allow operation of accessories when the engine is not running.

To act as a swamp to damp out Fluctuations of system voltage.

To allow dynamic memory and alarm systems to remain active when the vehicle is left for a period of time.

Choosing the correct batteryThe batteries for the vehicle is chosen under two major condition

The power in the battery must have ability to attain the minimal ignition speed of the Engine under cold condition.

It must have capability to run the electrical accessories when the Engine is at rest.

Hence the lead acid battery is mostly preferred for the vehicles.

Positioning the vehicle batterySeveral basic parameters should be considered while positioning the battery for

the vehicle.

Weight distribution of vehicle components.

Proximity to the starter to reduce cable length.

Accessibility.

Protection against contamination.

Ambient temperature.

Vibration protection.

Lead-acid batteriesEven after well over 100 years of development and much promising research into

other techniques of energy storage, the lead-acid battery is still the best choice for vehicles.

Incremental changes over the years have made the sealed and maintenance-free battery now in common use. Note that quality is often related to the price the customer pays. Many bottom-of-the-range cheap batteries, with a 12 month guarantee, will last for 13 months!

The basic construction of a nominal 12 V lead-acid battery consists of six cells connected in series. Each cell, producing about 2 V, is housed in an individual compartment within a polypropylene.

Cont… The active material is held in grids or baskets to form the positive and negative

plat`es. Separators made from a micro-porous plastic insulate these plates from each other.

The grids, connecting strips and the battery posts are made from a lead alloy.

Battery ratingThe rate at which a battery can produce current is determined by the speed of the

chemical reaction. This in turn is determined by a number of factors, they are.

• Surface area of the plates.

• Temperature.

• Electrolyte strength.

•Current demanded.

Reverse capacityReserve Capacity Minutes (RCM) also referred to as reserve capacity of the battery.

It is a ability of the battery to sustain a minimum stated electrical load.

It is defined as the time (in minutes) that a lead-acid battery at 80 °F (27 °C) will continuously deliver 25 amperes before its voltage drops below 10.5 volts.

It shows, how long will the battery work. If the charging system in the car is malfunctioned.

Typically, a 44 Ah battery should have the reverse capacity of 60 Minutes.

CCA• CCA stands for Cold Cracking Amp. Batteries are given a rating to indicate

performance at high current output and at low temperature. A typical value of 100 A means that the battery will supply this current for one minute at a temperature of 18 °C, at which point the cell voltage will fall to 1.4 V (BS – British Standards).

• The cold cranking amps (CCA) capacity rating methods do vary to some extent, they are. British standards, DIN standards and SAE standards are the three main examples.

STANDARD TIME(SECONDS)

BS 60

DN 30

SAE 30

MaintenanceBy far the majority of batteries now available are classed as ‘maintenance free’. This

implies that little attention is required during the life of the battery.

Earlier batteries and some heavier types do, however, still require the electrolyte level to be checked and topped up periodically.

Ensuring that the battery case and, in particular, the top remains clean, will help to reduce the rate of self-discharge.

The state of charge of a battery is still very important and, in general, it is not advisable to allow the state of charge to fall below 70%.

Charging the Lead acid batteryThere are three ways to charge the Lead acid batteries.

Constant-current charge.The constant-current charge applies the bulk of the charge and takes up roughly

half of the required charge time.

Topping charge.The topping charge continues at a lower charge current and provides saturation.

Float charge.The float charge compensates for the loss caused by self-discharge.

Servicing batteriesClean corrosion from terminals using

hot water.

Terminals should be smeared with petroleum jelly or Vaseline, not ordinary grease.

Battery tops should be clean and dry.

If not sealed, cells should be topped up with distilled water 3 mm above the plates.

The battery should be securely clamped in position.

SafetyThe following points must be observed when working with

batteries for safety

Good ventilation.

Protective clothing.

Supply of water available (running water preferable).

First aid equipment available, including eye-wash.

No smoking or naked lights permitted.