The battery provides electricity which ignites the fuel/air mixture in the engine's combustion chamber, the starter motor kicks in and you are off. Once the engine is running, the alternator supplies the electricity the vehicle needs, although the battery may also provide additional electricity when excessive energy requirements put the alternator under pressure. This type of battery is often referred to as an SLI – Start -Lights-Ignition.
The Lead-Acid Battery
A lead-acid battery has 6 series-connected galvanised cells arranged in a circuit. Each cell delivers 2.1 volts, so a total of 12.6 volts in total. Each cell comprises alternate plates of lead and lead coated with lead dioxide and they sit in an electrolyte solution of sulphuric acid. It is the chemical reactions caused by these components that produce the electric charge and the ability the battery possesses to re-charge itself. 12 volts is usually all a standard car requires, although trucks and other very large vehicles may require the power that comes from a 24- volt battery. The fluid levels in a modern battery remain pretty stable for the lifetime of the battery, so they don't need topping up with electrolyte in the way old ones once did. However, if the battery is drained, this can result in damage to the electrode plates which shortens the lifespan of the battery.
As the name implies, these are batteries suited to racing. A primary consideration is whether you are racing on the track or whether you are also racing on the road. If you are racing solely on the track, a smaller, lighter racing battery should provide all the power you need to get you off to a flying start. However, with on the road driving the call on the battery is much greater and you need to factor this in when you purchase your battery. On ignition, a battery designed for racing will provide a much higher output than a normal battery although they have less capacity overall. They are also built to withstand the shock and excessive vibrations that occur when racing.
A Lightweight Car Battery
If you are racing, you want your car to carry as little weight as possible. Whilst the difference between the weight of a standard battery and a lightweight battery may seem inconsequential, to a racing driver seeking that edge, it is important. Even for ordinary non-racing users, lightweight versions have their advantages. Over time, the reduction in weight can lead to a reduction in fuel consumption. If you are buying one of these, it should match as closely as possible the specification of a standard battery for your car in terms of voltage, amp hours and expected lifespan. Most lightweights are maintenance-free and are unlikely to cost more than a normal battery. Used as recommended, a modern battery should last for about 5 years.
The Cold Cranking Amp Capabilities of Batteries
One very important feature of all batteries is their CCA or cold cranking amp ability, which enables the battery to supply enough voltage to the spark plugs or coil pack to start the engine, every time, even in cold weather.
A battery charger plugs into your electricity supply and has two terminals that attach to your battery. They are particularly useful if your car has been unused for some months, for example, during the winter. It is important that you make sure that you buy a battery that will perform the functions you want it to:
Trickle charging – the charger supplies a very small amount of charge while the vehicle is in storage and will not be used for some time. The charge just keep the battery topped-up;
Conventional charging – Used to charge depleted a fully drained battery for between 6-12 hours; and
Engine Start Function – This is akin to starting your car with jump leads and the charger must have sufficient power to be able to effect this.