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Equipment Tests > Batteries
Batteries
Issue: May 2006
Words by Glenn Torrens
Power and the Glory
There are more to batteries than 12 volts and two terminals. Let Overlander 4WD guide you through the basics before you buy.
Most people know that a vehicle's battery is where the electricity hides while it's waiting to start your 4WD's engine and, teamed with the charging system, looks after the electrical power while a vehicle is being driven. The battery also supplies the juice required to run alarms and radio memory back-ups when the vehicle is parked, and radios, interior lights and other bits and bobs when the engine is off.
So what else do you need to know?
First up, you need to be aware of size, height and terminal location differences. Most vehicles require a specific 'format' of battery to be an easy, secure fit in the battery's standard underbonnet location and line up with the vehicle's standard wiring harness and battery terminals.
An Australian standard exists for batteries (AS2149) and in it, provides for several different case/terminal layouts to suit different cars.
There are also different designs of batteries depending on the power delivery required. Consider this:
• Starting a vehicle's engine requires a relatively large amount of power for a short time with immediate battery recharge from the vehicle alternator.
• Camping requires relatively small amounts of power, often with long periods between charging of the battery.
• Winching requires lots of power for an extended period - from 30 seconds to an hour or more.
To cater for this, batteries are designed for different tasks. On the flipside, using a battery for a task for which it is not designed can lead to the early death of the battery. Batteries have different internals and other construction differences that affect not only their use, but also their cost, durability and longevity.
Battery types
Most of us are familiar with conventional automotive starting batteries. These factory-fit batteries are designed to start your vehicle and cater for the day-to-day electrical demands from the vehicle. They are usually constructed of a bank of cells in a plastic case, with each cell consisting of thin metal plates swimming in acid - each known as a 'flooded wet cell'.
When a regular automotive starting battery is 'run flat' (or deep cycled), it loses some of its ability to perform. Put simply, it is never the same again. Some batteries will suffer badly from this treatment, with only a handful of incidences of running 'flat' rendering the battery next to useless. And the thing is, the battery doesn't have to be 'dead flat'. Many starts, followed by only short vehicle running times (with little opportunity for the battery to recover) can dip deep into the battery's reserve capacity and do damage.
That's why 'deep cycle' batteries were invented. Without getting too technical, deep cycle batteries soak up more electricity and deliver it for longer, making them more suitable for 'house' batteries, for use in camping and caravanning. But, they like to do it slowly. They don't like punching out big current so usually aren't suitable for vehicle starting. In general, they also require longer to recharge. That counts against them for some situations, as most vehicles don't run continuously for the 24 hours or more that these batteries like to fully charge.
What do the numbers mean?
Although most 4WDs - like most cars - have '12V' systems, they actually operate at a higher voltage - into the 14s. Heavy transport trucks often have 24V systems. The energy available in a battery is related to its measurable voltage and 11.5V (when measured at the terminals under no load) is generally regarded as the level that will allow the battery to start the vehicle - just one last time.
'Cold Cranking Amps' (CCA) is the number of amperes (put simply, the amount of effort) that can be continuously delivered by the battery. Just like most other devices, a battery's performance is affected by environmental factors and in this case, this test finds current available at minus 18 degrees Celsius while keeping voltage above 7.2V for 30 seconds. Typically, a standard automotive battery will be rated
to 430CCA or higher. Most manufacturers - vehicle and battery - specify a minimum CCA rating for a vehicle's battery to reflect requirements in cold conditions although, as with many situations, you can't have too much of a good thing. There's no harm in up-sizing your battery if it is to be used constantly in cold conditions.
'Reserve Capacity' (RC) is the amount of 'fuel' in the battery. It's measured by discovering how many minutes a battery can provide 25A before its voltage drops below a level that will adequately operate the vehicle's engine (typically 10.5V). This test replicates available vehicle driving time with a dead alternator. The number '85RC' on a battery means 85 minutes Reserve Capacity at 25A. The bigger this number, the longer you can drive with a broken alternator or drive belt.
'Amp hours' (AH) is a rating given to deep cycle batteries often used as house batteries for camping/caravanning (or remote area solar-powered domestic housing). It's the measure of how much current is available for 20 hours (some rate at 100 hours; under standard test conditions of 25 degrees) before battery voltage drops to 10.5V.
Think of cold cranking amps as how hard the battery punches, the voltage as the speed at which it swings those punches and the reserve capacity or amp hour rating, its stamina...
read on below advertisement
Battery building blocks
There is also the matter of physical toughness - vibration and shock resistance is especially relevant to the 4WD scene. Conventional flooded wet cell batteries don't like too much rock and roll - the plates can break free of the battery chassis and the electrolyte (acid) can spill.
Sealed lead acid batteries, or gel cells, are chemically similar to conventional batteries, but as the name implies, the electrolyte is present in the battery in a gel form rather than as a liquid. Not only does this add toughness, but also the gel reduces characteristics such as sulfation that leads to early death. Absorbed glass mat (AGM) batteries are a step ahead again. In each AGM cell, the electrolyte - acid - is present in a fine fibreglass mat.
AGMs cannot only deliver a big-CCA punch for vehicle starting, but they happily tolerate being discharged to around 30 percent capacity without significant deterioration. They are ideal dual-purpose - starting and house - batteries because they hold more useable power and don't mind dishing it out.
For 4WD use, any sealed lead acid battery is worth considering, and not just for performance reasons. Thanks to the fact they don't drop their guts, they don't prevent a vehicle being started after a rollover but do prevent injury and vehicle damage from spilled acid. Batteries designed for marine use are often the toughest of the lot. They are rated for complete inversion, immersion and ruggedness in a very hostile environment.
Spending the money to do things right when it comes to vehicle batteries can be the difference between great trip and a disastrous one.
WIRING
Wiring is a whole other subject, but it's important that any and all extra wiring (including terminals and fuses) be adequately rated for the power requirement. For instance, many enthusiasts run into problems with relocated batteries not being able to 'crank' the engine adequately as there is too much power loss (due to internal resistance) in the extra length of the battery/starter cables. Sourcing accessory power from the starter terminal (for instance, the coil or engine computer) can further complicate problems - the voltage available when the vehicle is being cranked may be below the threshold voltage these devices need to operate to run the engine.
MAINTENANCE
Many batteries these days are 'maintenance free' but like many other parts of your truck or car, a bit of love goes a long way. Terminals should be inspected for secure fitting and corrosion as loose or high-resistance terminals can lead to a wide variety of vehicle problems - from hard starting to inadequate charging to high-rev misfires. Make sure you know your 4WD's radio security code, the vehicle is unlocked and the ignition is OFF - plus any other requirements mentioned in the owners manual - before removing battery terminals. If there are inspection ports (battery caps) present, electrolyte levels should be checked and maintained to the correct height - learn what it is for your brand of battery. What's wrong with checking your battery every time you check your oil?
WHY DID MY BATTERY DIE?
Most batteries don't die - they are killed. Under-sizing for the vehicle, inadequate charging capacity (caused by undersized alternator for the expected load, or a slipping fan belt) or faulty voltage regulation conspire to keep the battery permanently discharged and lead to internal destruction from sulfation. Over-charging (due to faulty voltage regulation) will boil a battery dry in use as quickly as a $20 charger will. A loose retaining mount can quickly allow a battery to vibrate or smash itself to death, too. Many batteries die due to improper charging procedures, especially when conventional starting and deep cycle batteries exist in the one vehicle. But that's a story for another day...
CHARGING
Good rule of thumb - if it's been discharged slowly, charge it slowly and if it's been discharged quickly then pump charge into it fast. Once a battery is fully charged - typically overnight for a 'flat' starting battery - take it off the charger straight away. Most general-purpose chargers (i.e. cheap ones) will keep pumping power into a full-charged battery, causing it to 'boil' and abbreviating its life. 'Float' chargers - there are many brands available - can remain connected to keep an occasional-use battery fully charged and ready for work without doing damage.
COLD CASE
Cold weather affects a battery's performance because a battery is a big box of chemicals and chemical reactions don't happen as quickly when it's cold and that makes power delivery sluggish. Cold engines with thick oils require more grunt to start, too. Although a warm battery might be happier to start your truck than a cold one, too much heat has a detrimental effect. The reason is simple - the liquid electrolyte evaporates quicker when things are warm.
FAIL-SAFE
Many boats have a permanently wired link switch that allows the house battery to be used for emergency starting in case of failure. This switch will isolate the starting battery - to prevent the dud starter battery from pulling power from the house battery - and allow emergency starting. It's worth considering for inclusion in a second battery system in a 4WD. Heavy-duty batteries designed for marine environments have their cells anchored properly to the case to prevent damage. It's a tough ride in a tinny...
Words by Glenn Torrens
Power and the Glory
There are more to batteries than 12 volts and two terminals. Let Overlander 4WD guide you through the basics before you buy.
Most people know that a vehicle's battery is where the electricity hides while it's waiting to start your 4WD's engine and, teamed with the charging system, looks after the electrical power while a vehicle is being driven. The battery also supplies the juice required to run alarms and radio memory back-ups when the vehicle is parked, and radios, interior lights and other bits and bobs when the engine is off.
So what else do you need to know?
First up, you need to be aware of size, height and terminal location differences. Most vehicles require a specific 'format' of battery to be an easy, secure fit in the battery's standard underbonnet location and line up with the vehicle's standard wiring harness and battery terminals.
An Australian standard exists for batteries (AS2149) and in it, provides for several different case/terminal layouts to suit different cars.
There are also different designs of batteries depending on the power delivery required. Consider this:
• Starting a vehicle's engine requires a relatively large amount of power for a short time with immediate battery recharge from the vehicle alternator.
• Camping requires relatively small amounts of power, often with long periods between charging of the battery.
• Winching requires lots of power for an extended period - from 30 seconds to an hour or more.
To cater for this, batteries are designed for different tasks. On the flipside, using a battery for a task for which it is not designed can lead to the early death of the battery. Batteries have different internals and other construction differences that affect not only their use, but also their cost, durability and longevity.
Battery types
Most of us are familiar with conventional automotive starting batteries. These factory-fit batteries are designed to start your vehicle and cater for the day-to-day electrical demands from the vehicle. They are usually constructed of a bank of cells in a plastic case, with each cell consisting of thin metal plates swimming in acid - each known as a 'flooded wet cell'.
When a regular automotive starting battery is 'run flat' (or deep cycled), it loses some of its ability to perform. Put simply, it is never the same again. Some batteries will suffer badly from this treatment, with only a handful of incidences of running 'flat' rendering the battery next to useless. And the thing is, the battery doesn't have to be 'dead flat'. Many starts, followed by only short vehicle running times (with little opportunity for the battery to recover) can dip deep into the battery's reserve capacity and do damage.
That's why 'deep cycle' batteries were invented. Without getting too technical, deep cycle batteries soak up more electricity and deliver it for longer, making them more suitable for 'house' batteries, for use in camping and caravanning. But, they like to do it slowly. They don't like punching out big current so usually aren't suitable for vehicle starting. In general, they also require longer to recharge. That counts against them for some situations, as most vehicles don't run continuously for the 24 hours or more that these batteries like to fully charge.
What do the numbers mean?
Although most 4WDs - like most cars - have '12V' systems, they actually operate at a higher voltage - into the 14s. Heavy transport trucks often have 24V systems. The energy available in a battery is related to its measurable voltage and 11.5V (when measured at the terminals under no load) is generally regarded as the level that will allow the battery to start the vehicle - just one last time.
'Cold Cranking Amps' (CCA) is the number of amperes (put simply, the amount of effort) that can be continuously delivered by the battery. Just like most other devices, a battery's performance is affected by environmental factors and in this case, this test finds current available at minus 18 degrees Celsius while keeping voltage above 7.2V for 30 seconds. Typically, a standard automotive battery will be rated
to 430CCA or higher. Most manufacturers - vehicle and battery - specify a minimum CCA rating for a vehicle's battery to reflect requirements in cold conditions although, as with many situations, you can't have too much of a good thing. There's no harm in up-sizing your battery if it is to be used constantly in cold conditions.
'Reserve Capacity' (RC) is the amount of 'fuel' in the battery. It's measured by discovering how many minutes a battery can provide 25A before its voltage drops below a level that will adequately operate the vehicle's engine (typically 10.5V). This test replicates available vehicle driving time with a dead alternator. The number '85RC' on a battery means 85 minutes Reserve Capacity at 25A. The bigger this number, the longer you can drive with a broken alternator or drive belt.
'Amp hours' (AH) is a rating given to deep cycle batteries often used as house batteries for camping/caravanning (or remote area solar-powered domestic housing). It's the measure of how much current is available for 20 hours (some rate at 100 hours; under standard test conditions of 25 degrees) before battery voltage drops to 10.5V.
Think of cold cranking amps as how hard the battery punches, the voltage as the speed at which it swings those punches and the reserve capacity or amp hour rating, its stamina...
read on below advertisement
Battery building blocks
There is also the matter of physical toughness - vibration and shock resistance is especially relevant to the 4WD scene. Conventional flooded wet cell batteries don't like too much rock and roll - the plates can break free of the battery chassis and the electrolyte (acid) can spill.
Sealed lead acid batteries, or gel cells, are chemically similar to conventional batteries, but as the name implies, the electrolyte is present in the battery in a gel form rather than as a liquid. Not only does this add toughness, but also the gel reduces characteristics such as sulfation that leads to early death. Absorbed glass mat (AGM) batteries are a step ahead again. In each AGM cell, the electrolyte - acid - is present in a fine fibreglass mat.
AGMs cannot only deliver a big-CCA punch for vehicle starting, but they happily tolerate being discharged to around 30 percent capacity without significant deterioration. They are ideal dual-purpose - starting and house - batteries because they hold more useable power and don't mind dishing it out.
For 4WD use, any sealed lead acid battery is worth considering, and not just for performance reasons. Thanks to the fact they don't drop their guts, they don't prevent a vehicle being started after a rollover but do prevent injury and vehicle damage from spilled acid. Batteries designed for marine use are often the toughest of the lot. They are rated for complete inversion, immersion and ruggedness in a very hostile environment.
Spending the money to do things right when it comes to vehicle batteries can be the difference between great trip and a disastrous one.
WIRING
Wiring is a whole other subject, but it's important that any and all extra wiring (including terminals and fuses) be adequately rated for the power requirement. For instance, many enthusiasts run into problems with relocated batteries not being able to 'crank' the engine adequately as there is too much power loss (due to internal resistance) in the extra length of the battery/starter cables. Sourcing accessory power from the starter terminal (for instance, the coil or engine computer) can further complicate problems - the voltage available when the vehicle is being cranked may be below the threshold voltage these devices need to operate to run the engine.
MAINTENANCE
Many batteries these days are 'maintenance free' but like many other parts of your truck or car, a bit of love goes a long way. Terminals should be inspected for secure fitting and corrosion as loose or high-resistance terminals can lead to a wide variety of vehicle problems - from hard starting to inadequate charging to high-rev misfires. Make sure you know your 4WD's radio security code, the vehicle is unlocked and the ignition is OFF - plus any other requirements mentioned in the owners manual - before removing battery terminals. If there are inspection ports (battery caps) present, electrolyte levels should be checked and maintained to the correct height - learn what it is for your brand of battery. What's wrong with checking your battery every time you check your oil?
WHY DID MY BATTERY DIE?
Most batteries don't die - they are killed. Under-sizing for the vehicle, inadequate charging capacity (caused by undersized alternator for the expected load, or a slipping fan belt) or faulty voltage regulation conspire to keep the battery permanently discharged and lead to internal destruction from sulfation. Over-charging (due to faulty voltage regulation) will boil a battery dry in use as quickly as a $20 charger will. A loose retaining mount can quickly allow a battery to vibrate or smash itself to death, too. Many batteries die due to improper charging procedures, especially when conventional starting and deep cycle batteries exist in the one vehicle. But that's a story for another day...
CHARGING
Good rule of thumb - if it's been discharged slowly, charge it slowly and if it's been discharged quickly then pump charge into it fast. Once a battery is fully charged - typically overnight for a 'flat' starting battery - take it off the charger straight away. Most general-purpose chargers (i.e. cheap ones) will keep pumping power into a full-charged battery, causing it to 'boil' and abbreviating its life. 'Float' chargers - there are many brands available - can remain connected to keep an occasional-use battery fully charged and ready for work without doing damage.
COLD CASE
Cold weather affects a battery's performance because a battery is a big box of chemicals and chemical reactions don't happen as quickly when it's cold and that makes power delivery sluggish. Cold engines with thick oils require more grunt to start, too. Although a warm battery might be happier to start your truck than a cold one, too much heat has a detrimental effect. The reason is simple - the liquid electrolyte evaporates quicker when things are warm.
FAIL-SAFE
Many boats have a permanently wired link switch that allows the house battery to be used for emergency starting in case of failure. This switch will isolate the starting battery - to prevent the dud starter battery from pulling power from the house battery - and allow emergency starting. It's worth considering for inclusion in a second battery system in a 4WD. Heavy-duty batteries designed for marine environments have their cells anchored properly to the case to prevent damage. It's a tough ride in a tinny...
