Virtual Mechanic

Batteries must be subjected to regular testing to ensure their starting capacity is maintained at an optimum performance level.  A battery must also be scrutinised for any physical condition which may reduce battery life and impede starting performance such as broken or damaged posts and leaks to the battery case or lid

The first step in evaluating starting capacity involves testing a battery’s state of charge using a hydrometer or voltmeter.  All non-sealed batteries should be checked using a hydrometer.  As a cheap and reliable method of determining state of charge, the hydrometer also reveals differences between cells and allows visual inspection of the electrolyte colour.  Where the hydrometer reading shows no significant difference between cells and produces a reading of 1230 or above (at 20-25C) the battery has sufficient charge for a load test.

Sealed batteries must produce a voltage of 12.5 or greater before a load test may be performed.  Since the loss/fail criteria varies depending on the make of load tester used, be sure to consult the instruction manual provided with the tester to ensure success.

Battery Testing

This article is found in the Virtual mechanic CD Rom
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By Darren Gow-Brown, Melbourne Australia

Batteries contain highly corrosive sulphuric acid and explosive hydrogen and oxygen gases.  Batteries must be handled with extreme care at all times.

Handling battery acid
When working with acid, such as filling batteries, use a face shield.  If many batteries are handles, wear protective clothing for extra safety.

Extreme care must be taken to avoid spilling or splashing electrolyte since it can destroy clothing and burn the skin.

Care should also be taken when lifting and carrying batteries.  If excessive pressure is placed on the end walls of a plastic cased battery, it could cause electrolyte to seep through the vents.  A battery carrier should always be used, otherwise batteries may be lifted with your hands carefully placed at opposite corners.  If electrolyte is spilled or splashed it must be neutralised immediately and then rinsed with clean water.  Baking soda or household ammonia mixed with water makes an effective neutraliser.

Electrolyte splashed into the eyes is extremely dangerous.  If this should happen, force the eye open and floor it with cool, clean water for approximately 15 minutes.  A doctor should be called to the scene for immediate medical attention. 

However, if this is not possible, follow the doctor’s instructions to take emergency action.  Do not add eye drops or other medication unless advised to do so by the doctor.

Be sure batteries and acid are placed well away from a child’s reach.  If acid is taken internally drink large quantities of water or milk.  Follow with milk of magnesia, beaten egg or vegetable oil.  Call a doctor immediately.

If electrolyte is spilled or splashed on any surface of the car, it should be neutralised and rinsed with clean water.

If it becomes necessary to prepare electrolyte of a desired specific gravity, always pour the concentrated acid slowly into the water – do not pour water into the acid.  Heat is generated when acid is mixed with water.  Add small amounts of acid slowly while stirring.  Allow to cool if noticeable heat develops.  Except for lead or lead lined containers, use non-metallic receptacles and/or funnels.  Do not store acid in excessively warm locations or in direct sunlight.

Danger of exploding battery
Batteries generate explosive gases.  It only takes a small spark, flame or burning cigarette to set off a dangerous explosion.  Therefore, these and other ignition sources must be kept well away at all times.
Hydrogen and oxygen gases are produced during normal battery operation and escape through the battery vents.  Make sure working areas are well ventilated to avoid creating an explosive atmosphere around the battery.

Ensure safety precautions continue to be observed after a battery has been charged as explosive gases may still be present for several hours.

An exploding battery may cause serious injuries including eye injury from flying pieces of the case or cover.  Always wear safety goggles and a face shield when working near batteries.

Never lean over the battery during charging, testing or “jump starting” operations.

Do not break “live” circuits at the terminals of batteries because a spark invariably occurs at the point where a “live” circuit is broken.

Make certain the charger cable clamps or booster leads are clean and making good connections.  A poor connection can cause an electrical arc which could ignite the gas mixture and explode the battery.

Take care to ensure tools or other metallic objects do not fall across the terminal or any adjacent metallic part of the vehicle.

Do not smoke when working under the hood of a car or near a battery.  Never strike a match or bring any other flame near a battery.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia

SAE Cranking Current
The Society of Automotive Engineers (SAE) defines starting power as the “SAE Cranking Current” or Cold Cranking Amps (CCA) which is the internationally recognised industry standard to determine battery starting capability.  The cold cranking test is conducted at – 18C to simulate very cold, difficult to start conditions.  The battery’s ability to perform is measured by the amount of current the battery can deliver over a short period of 30 seconds (referred to as the 30 second rate) while maintaining a voltage equivalent of 1.2 volts per cell or higher.  Therefore, a 12 volt battery must maintain a voltage equivalent of 7.2 and 3.6 for a 6 volt battery.

Reserve Capacity
A battery’s reserve capacity must sustain a minimum electrical load for ignition, headlights, windshield wipers and defroster under cold winter conditions in the event of a charging system failure.

The reserve capacity rating represents the number of minutes at 25C a battery can supply a load of 25 Amps and maintain a voltage of 1.75 volts or higher per cell.  (10.5 volts for a 12 volt battery of 5.25 volts for a 6 volt battery).

Amp Hours
No longer in popular use as a standard for rating automotive batteries, the “Amp Hour” rating represents the current a battery can supply for 20 hours.  For example, a 50 Amp hour battery supplies 2.5 Amps for 20 hours.  2.5 Amps x 20 hours = 50 Amp hours.  The standard was abandoned because it fails to rate the starting capability of a battery and its ability to power a typical accessory load.

The Amp hour rating does have benefits with regard to cycling batteries.  A battery’s efficiency varies depending on the rate of discharge.  The rating for cycling batteries uses Amp hours at three separate rates of discharge (see table).

20 hr 50 Amp Hrs (2.5 amp x 20 hrs)
  5 hr 41 Amp Hrs (8.2 amp x 5 hrs)
  2 hr 34 Amp Hrs (17 amp x 2 hrs)

Plates per Cell
In the past, it was assumed that “The more plates the greater the power”.  Therefore, “An 11 plate battery is more powerful than a 7 plate battery”.  Plates per cell has been discarded as a measure of battery performance because the size of the plates is more relevant to performance than the number of plates.  The area of plates determines starting power and the weight of active material determines reserve capacity.

A large number of thin plates that are small in surface area are likely to have less cranking power and less reserve power than a small number of thick plates that are large in area.
This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia

Although the average life of car batteries has increased to 42 months under normal operating conditions, a battery’s life can be reduced by factors involving storage, vibration, temperature conditions, overcharging and cycling.

Storage
Batteries have a limited shelf life and when stored gradually lose their power to perform.  On average, a fully-charged battery takes about 13 weeks to gradually discharge to less than its optimum operating level.  The rate of charge loss depends on battery type (low maintenance or maintenance free) and temperature conditions.
Charge loss becomes more evident when temperatures increase.  At 20C low maintenance batteries lose approximately one half of one percent of charge per day (30 percent in 60 days).  At 30C charge loss is usually double the rate for 20C.

Under similar temperature conditions, maintenance free batteries lose their charge more slowly than low maintenance batteries.  Excessive humidity will also accelerate charge loss.  Batteries stored upright in cool and dry conditions is ideal.

Whilst in storage batteries have not been recharged and allowed to go flat, may be permanently damaged.  Recharging every four to eight weeks, depending on storage conditions, will restore batteries to “as new” condition.

Vibration
Vibration loosens active material from the battery plates which may cause shorting and can also damage the structural integrity of battery connections.

Overcharging
Overcharging permanently damages batteries, therefore overcharging corrodes the grid mesh and accelerates loss of active material from the positive plate.  It also deteriorates separators and increases water loss.

High temperature
A higher temperature requires higher charge rates which leads to an accelerated loss of active material from the positive plates, as well as separator deterioration, increased grid corrosion and water loss.

Cycling
Charging and recharging causes expansion and contraction of positive active material which leads to increased shedding.  The depth and frequency of discharge influences the amount of deterioration.

Sulphation
Sulphation occurs when a battery is stored over a long period of time in a state of low charge.  The crystalline structure of the discharged active material, (lead sulphate), is gradually transformed into a substance which resists recharge, causing permanent deterioration.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia

A battery is an efficient and compact energy storage centre created by a manufacturing process that combines chemicals, grids, plates and separators to produce electrical power.  Within each cell a battery houses a group of alternate positive and negative plates held apart by separators and bathed in electrolyte.
Since each cell supplies approximately 2.1 volts, a six volt battery would contain three cells connected in a series.  Six cells would prove a “12 volt” battery (actually 12.6 volts).  The size, thickness and number of plates in each cell determines a battery’s capacity.
Taking a look inside a typical battery you will find:

Chemicals
A lead acid battery contains four chemicals:
· Lead – Which is used to make the grids, straps, posts etc.  It is also used in a sponge form as the active material found on negative plates.
· Antimony – Only a small amount of antimony is necessary to harden the grids which would normally be soft and easy to bend.
· Lead Peroxide – Manufactured by oxidising pure lead electrochemically, lead peroxide is the active material found on positive plates.
· Sulphuric Acid – Diluted sulphuric acid forms the electrolyte acid solution which contains about 25% sulphuric acid and 75% water by volume.  This corresponds to a specific gravity of 1.260 at 25C.

Grids
The grids within a battery compose a solid framework designed to hold the active material in place.  Cast of lead and antimony, the grids also conduct the electrical current produced by the active materials to the battery terminals.

Plates
Positive plates are grids covered in a lead peroxide past and are dark brown in colour.  Negative plates are pasted with grey sponge lead.  The negative sponge lead and the positive lead peroxide create the two different metals necessary to enable a lead acid storage battery to produce electricity.

Separators
Separators prevent positive and negative plates from making contact, which results in shorting causing the battery to self discharge.  Separators are thin sheets of non-conducting porous plastic material which are inserted between the plates or completely encasing a positive or negative plate.  A rib faces the positive plates and provides greater electrolyte volume in addition to minimising the area of contact with the positive plates.  Many batteries also feature glass fibre retaining mats placed between the positive plate and the separator to slow the loss of active material from the plate.

Electrolyte
The sulphuric acid in the electrolyte is absorbed within the positive and negative plates, producing a chemical reaction which is then released as electrical power.  The electrolyte also carries the electrical current within the battery between the positive and negative plates passing through the separators.

Container
The container houses the pates, separators and electrolyte.  Usually constructed of polypropylene, it must withstand extreme heat and cold as well as shock and vibration.  Bridges at the bottom allow a space for the active material to settle during battery life without the danger of shorting.

Element Construction
The desired number of positive and negative plates are interleaved with separators to form an element or group.  Like plates are welded together at the plate lugs.  Each element connects to the one adjacent to it in a series (positive to negative).  For greater performance there is always one more negative plate than positive.
Any number or size of plate may be used in an element, depending upon how much energy needs to be stored.  Of course, increasing the size and number of plates creates a higher ampere rate during discharge at low temperatures.  (ie: a high CCA rating)

Connecting elements together
Connectors are used to connect al the elements together to form a series within each cell.  They are designed to carry a much higher current than normally required to ensure melting does not occur when starting.

Three types of connectors are used including:

“Conventional old style” connectors which connect elements together on top of the battery.
“Loop-over” connectors which use straps to loop over the cell dividers and are welded and placed under the cover.

“Through the partition” connectors which are made directly through the cell wall and are sealed by crimping under high pressure and lead welding.  This is by far the most common method used.

Covers and vent caps
Covers and vent plugs prevent electrolyte spillage and keep out dirt and other impurities.  A cover may have three or six vent holes depending on the number of cells.  Generally, heat and pressure is used to seal them to the container.  A vent cap closes the vent holes and provides a convenient way to check the electrolyte level.  Vent caps also allow gas to escape when charging the battery.  Some are fitted with a porous disc to prevent externally induced explosions.

Terminals
Terminals are the battery’s external electrical connection points and are normally located on top of the battery.  They are moulded into the cover and connect internally to the post in the two end groups.  To minimise the danger of installing a battery in reverse, the positive terminal is slightly larger than the negative terminal.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia

Batteries produce their power through a chemical reaction which is released when a load, such as a light globe, starter motor or electric fan, is connected to the battery.  As was observed more than 100 years ago, when two different metals are placed in a liquid capable of conducting electricity, and the metals are connected together above the liquid, electrical current flows through the connection.

The different metals are referred to as electrodes.  Pure lead is used for the negative electrode or plate and a lead dioxide paste is used for the positive electrode.  When combined, they are referred to as a cell.  Two or more cells connected together are called a battery.  The liquid solution is called an electrolyte which consists of a diluted solution of sulphuric acid.  The battery becomes discharged or flat when no more current flows through the cell.  The cell can be recharged by forcing electrical current back through the cell in the reverse direction.

The chemical reaction that takes place during discharge converts both the positive electrode and the negative electrode to lead sulphate.  Water is produced and dilutes the strength of the acid.

The chemical reaction is written as follows:

During recharge the electrodes are converted back to lead dioxide and lead.  The water produced during discharge is consumed, returning the acid to its original strength.  In addition, some electrolysis of the water in the electrolyte occurs breaking it down into its component gases, hydrogen and oxygen.

The rate at which the gasses are produced is greatest when the battery reaches a fully charged state.  Also the higher the charging current, the more gas produced.

Batteries have a series of vent flues that allow the gas to escape the system.  Hydrogen gas is highly volatile and sparks or flame can easily ignite the gas and cause an explosion.  Therefore great care must be taken to adhere to established safety precautions, especially when recharging.

A battery’s electrical pressure or electromotive force is measured in volts.  The flow of electrical current is measured in amperes.  The mathematical relationship between electrical power and its components is as follows:

(Volts are represented by the symbol  ‘V’, amps  ‘I’ and power or watts  ‘P’.)
                      P      =    IV
                  Watts    =   Amps x Volts
         or      Amps    =   Watts
                                    Volts
         or      Volts     =   Watts
                                   Amps

Also, “Ohm’s Law” expresses a mathematical relationship between volts, amperes and resistance (Ohms) in an electrical circuit.

                  Ohms   =    Volts
                                   Amps
         or       Volts   =    Ohms x Amps
         or       Amps  =    Volts
                                   Ohms

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia

Today’s automotive battery has undergone an evolution of change since its humble beginnings more than 180 years ago.  But some of the most significant changes have occurred in only the last ten years.

Modern cars demand more powerful batteries to cope with advances such as electronic ignition systems, on-board computers, air conditioning, mobile phones and central locking.  Compared to 30 years ago when the average car produced a typical total load of 275-300 watts, today an average car can produce a total need of 1500-2000 watts, (with all electrical accessories turned on).

This significant increase in demand prompted a dramatic shift in the method of determining battery power.  In the past, a battery’s power was determined by the number of plates per cell which proved to be misleading.  As technology changed and times became more competitive, manufacturers started reducing the size of batteries.  Although the number of plates remained constant, the area of lead, the true determinant of a battery’s power, was reduced.

As a result, Cold Cranking Amps (CCA) ratings are now the internationally recognised industry standard for accurately determining true battery starting power.  The higher the CCA rating, the more powerful the battery producing higher starting voltages to meet the demands placed upon it.

CCA ratings required for powering the average Australian car have also steadily increased from 220-250 CCA in 1960, to 375-400 CCA in 1990.  A battery purchased below the original equipment specification set by the car manufacturer is considered undersized and will result in a shorter battery life, reduced cranking power and increased starter motor power draw.

Another Significant advancement has been the appearance of the maintenance free and low maintenance type battery.  The low maintenance battery was developed using grids of plates manufactured from a combination of lead and alloys.  As a result, it only requires the addition of electrolyte only once per year.  The maintenance free battery does not require the addition of electrolyte for the normal life of the battery due to an even more refined grid construction.
This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia

Most people are familiar with the conventional “SLI” ) Starting, Lighting and Ignition) lead-acid battery which delivers the high amp energy necessary to provide maximum starting power.  Once the engine has started, the alternator recharges the battery.  However, repeated cycling, as well as the continual process of discharging and recharging, eventually weakens the :SLI: battery which provides concentrated starting power, the deep cycle type battery supplies a constant but relatively low amount of current for a long period of time when an extended power supply is preferred.

Battery technology covers every automotive need from original equipment for Australian manufactured vehicles to batteries designed to suit specialised requirements.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia

In addition to providing the starting power required, the automotive battery also supplies power to accessories such as lights, fans and radio when the engine is not running.  Between low engine speeds and when accessory load is greater at high running speeds, a battery makes up the difference by stabilising the alternator output.

This stabilising effect also protects a vehicle’s electrical system by smoothing out sudden high voltages which can damage electrical components.

Ask the average battery purchaser this question and most would say that a battery is simply the source of power necessary to start the engine of every motor driven vehicle.  Since most purchases are unplanned for, consumers usually have little knowledge or understanding about one of the most vital components of an automobile – the very essence of its electrical power.

With the increased demand of today’s technologically advanced cars, a basic understanding of the automotive battery, how it works and how to maintain it to ensure maximum performance and safety has become more important than ever.

The automotive storage battery falls under the category of a secondary battery.  Secondary batteries are rechargeable, unlike a primary battery which is not rechargeable and used to power devices such as flashlights and transistor radios.

This article is found in the Virtual mechanic CD Rom

Batteries what are they ?