Why do batteries fail
Batteries have a finite life, determined by the application and the operating conditions. Battery failure can be attributed to various factors, however the causes of failure fall under two distinct categories: manufacturing and non manufacturing faults.
Internal Short Circuit / Dead Cell
This is when contact is made between the positive and negative plates causing a cell to discharge, resulting in a drop in voltage and battery failure.
Non manufacturing faults
Wear and Tear
As a battery ages, grid metal corrodes and active material is lost from the plate. Over time this leads to a point where the battery will no longer be able to start a vehicle. High temperature will accelerate degradation rates.
Incorrect fitment, handling and storage often leads to external damage and subsequent battery failure. Examples include over tightening the terminal leads or battery hold down bracket and dropping or knocking the battery casing.
Fitting a smaller, lower capacity battery or a battery designed for another application can lead to early failure.
Lack of Maintenance
Failing to regularly maintain the battery's state of charge, fluid levels or terminal connections will accelerate battery failure.
Lead acid batteries must be kept charged at all times. The leading cause of early battery failure comes from undercharging. Prolonged undercharging from short journeys and stop-start driving can cause plate sulphation and acid stratification which reduce battery life.
Excessive voltage and current is the primary cause of overcharging. This can happen due to a faulty charging system or if the charging output is not compatible with the battery. Temperature can also increase the chances of overcharging, especially when the battery is inadequately ventilated or under bonnet in a constant high temperature environment.
Over Discharge / Heavy Cyclic Use
The deeper a battery is discharged the shorter its life. Even deep cycle batteries should not be discharged below 50% of their capacity before recharging is required. A battery being discharged to 100% of its capacity regularly will cause permanent damage to the internals of the battery.
Batteries installed in applications that are exposed to high levels of vibration from moving equipment, uneven road conditions, unsecure fitment or engine harmonics can be detrimental to the life of the battery. It is important to install a battery that is designed to handle these conditions.
Exposure to High Temperatures
As the temperature increases, so does the chemical reaction inside the battery, leading to an increased rate of corrosion. High temperature increases gassing & water loss in the battery, leading to further self - discharge. Batteries in high temperature environments need to be well ventilated and have temperature compensation to reduce the output as the temperature rises, to avoid overcharging.
Factors affecting battery life
As batteries operate and age, they gradually lose their capacity. The constant charge and discharge process eventually leads to failure. Components corrode over time, electrical shorts occur and vibration causes damage; eventually causing failure. Overcharging and undercharging of a battery will also have a bearing on battery life.
Early Warning Signs
Batteries often fail when least expected and can be avoided with regular battery testing. Time plays a key indicator, too often motorists hold off replacing the battery and end up inconvenienced by a roadside breakdown. The average life of a car battery is 42 months, after this the battery is on borrowed time and should be replaced.
Typical warning signs include a slower than normal ability to crank the engine. Other less noticeable factors, such as changed driving patterns and colder/hotter weather will all have an effect on the life of a battery. Regular battery testing can identify suspect batteries before they fail and avoid the inconvenience of a roadside breakdown.
Check electrolyte levels of a maintainable battery – fluid below the tops of the separators indicate overcharging or poor maintenance. Overcharging conditions may be due to an incorrect voltage setting, low voltage caused by heat or internal defects, or old age deterioration.
Check the Charge Indicator on a sealed maintenance free battery - this gives you a snap shot of the batteries condition and whether the battery needs to be charged or replaced.
Is there electrolyte on the top of the battery?
This can indicate overcharging or overfilling.
Is the battery loose in the carrier?
This can cause failure from vibration.
Does the battery have signs of damage or mistreatment?
This can also cause failure. Discharged (flat) Batteries A flat battery should be checked using the Charge Indicator on top of the battery or with a voltmeter or hydrometer depending on the type of battery. A low specific gravity reading of 1.240 or less in all cells indicates a discharged battery and it must be charged before further examination and testing can occur. The discharged condition may be due to a problem in the electrical system (slipping alternator belt, faulty regulator or alternator, high resistance due to corrosion). Internal shorts may also be due to manufacturing defects, the ageing process or vibration damage.
Vibration can reduce a battery’s life. Always use an approved battery clamp to limit vibration. Yuasa batteries are built tough, using robust internal components to resist damage through abrasion and puncture from vehicle vibration.
Many alleged ‘dead batteries’ are merely flat batteries. Drivers simply leave lights on or can have faulty voltage regulators.
Ensure your battery is properly tested before replacing it.
It’s difficult to know exactly when a battery might fail. A slow starting engine is sometimes an indication.
Old batteries can give trouble in colder weather.
Equally, if an engine area becomes overheated in very hot temperatures and the battery is under strain from air conditioners it may fail. Regular battery checks are always advised.
Battery care & maintenance
Use the following as a guide when examining your battery:
Check the battery's state of charge. Most batteries have a Charge Indicator on top of the battery that will give you an on the spot diagnosis of the battery condition. However, a more reliable way to check is with a voltmeter to determine the stabilised voltage or if the vent caps are removable a hydrometer to determine the specific gravity (SG) of the electrolyte. A charged Century battery will have a stabilised voltage above 12.5 volts and an SG reading above 1.240
Ensure the battery top is clean, dry, free of dirt and grime. A dirty battery can discharge across the grime on top of the battery casing.
Inspect the terminals, screws, clamps and cables for breakage, damage or loose connections. These should be clean, tight and free of corrosion.
Apply a thin coating of high temperature grease to posts and cable connections for added protection.
Inspect the battery case for obvious signs of physical damage or warpage. This usually indicates the battery has been overheated or has been overcharged.
If you have a maintainable battery, it is important to check if the battery has sufficient electrolyte covering the battery plates. If topping up is required, do not over fill as the fluid levels will rise when the battery is fully charged and may overflow. Top up using distilled or demineralised water and never fill with sulphuric acid.
When servicing a sealed maintenance free (SMF) battery, check the Charge Indicator. The Charge Indicator gives you a snap shot of the batteries condition and whether the battery needs to be charged or replaced. The vehicle may still start the engine although the indicator outlines to replace the battery.
If the charge indicator advises 'Replace Battery' it is important that the battery is replaced as the electrolyte levels may be below the plates which can lead to an internal explosion.
For batteries used in seasonal applications and stored long term, fully recharge the battery prior to storing. Check the state of charge or voltage regularly. Should the voltage drop below 12.5V, recharge the battery. It is important to check the battery completely before reconnecting to electrical devices.
^ Always follow manufacturers guideline
Battery health & safety
Battery acid can cause burns. Suitable hand, eye and face protection and protective clothing must be worn.
For advice, contact the poisons information centre or a doctor immediately. If in eyes, hold eyelids apart and flush the eye continuously with running water.
Continue flushing until advised to stop by poisons information centre or doctor, or at least 15 minutes. If skin or hair contact occurs, remove contaminated clothing and flush skin or hair with running water.
Acid Spill Response
Bund and neutralise spills with soda ash or other suitable alkali. Dispose of residue as chemical waste or as per local requirements.
If Electrolyte is Swallowed
Do NOT induce vomiting – give a glass of water. Seek immediate medical assistance.
Batteries generate explosive gases during vehicle operation and when charged separately. Flames, sparks, burning cigarettes or other ignition sources must be kept away at all times. Exercise caution when working with metallic tools or conductors to prevent short circuits and sparks.
Always Shield Eyes When Working Near Batteries
When charging batteries, work in a well ventilated area - never in a closed room & always turn battery charger or ignition off before disconnecting a battery.
Battery testing should be considered an integral part of any periodic vehicle maintenance routine and should be performed whether or not a starting problem has occurred.
Due to the increased electrical demands on the battery, little warning is given before failure. Pre-emptive battery replacement can help eliminate many of the costs and problems associated with a flat or end of life battery.
Before testing a battery, it is important that the battery is fully charged. Even a slightly discharged battery can give a false reading and deem the battery faulty when all that is required is a recharge.
There are many different types of testing equipment available. A digital battery tester is the preferred option as they are safe, easy to use and offer a quick diagnosis of the condition of the battery.
Fixed and adjustable load testers, voltmeters, hydrometers and discharge testers can also be used, however correct training is required prior to using any of these testers to prevent personal injury or damage to the vehicle.
Digital Battery Testers
Microprocessor controlled digital battery testers are easy to use, very safe and can help determine early battery failure. The tester works by transmitting a small signal through the battery that uses measurements of conductance or resistance (impedance) to indicate battery condition.
Most models provide battery, starting and charging tests. Printer options enable results to be given to the customer.
The state-of-charge of a lead acid battery can be determined by the specific gravity (SG) of the electrolyte (its density compared to a reference such as water). The SG can be measured directly with a hydrometer or indirectly by the stabilised voltage with a voltmeter. Please note the temperature of the acid affects the result.
Adjustable Load Testers
Adjustable load testers are a reliable method to determine the starting capacity of a battery, as the test applies a real load similar to when cranking the engine. This load however does create a spark risk if leads are connected to corroded or loose terminals. The standard test is to load the battery to 50% of its CCA rating (Cold Cranking Amperes) for 15 seconds. If the voltage reads above 9.6 volts the battery is ok.
For example a battery that has a CCA rating of 600 should be tested at 300CCA for 15 seconds. The standard interpretation of the result is that if, at the end of the 15 second test, the loaded voltage reading is between 9.6V and 10.6V then the battery is deemed to be good. If the result is under 9.6V the battery is not good and may not crank the engine.
It is always recommended that you check the individual manufacturer’s specifications.
Constant Rate Discharge Testers
Discharge testers are a simple method to check the capacity of a battery and are commonly carried out on deep cycle batteries. The tester works by discharging the battery at a pre-set current (Amps) until it drops to a pre- set disconnect voltage.
The biggest concern with this type of tester is the time it takes to perform the test.
As an example, if you were testing a 100 Ah (Ampere Hour) battery at 5 Amps, it could take up to 20 hours to complete the test.