Car batteries are an essential piece of equipment within a car. They provide the initial power for the car when you start it up. Before the car battery came about there used to be cranks that you would have to manually turn to kick start the engine and get it going. However modern times have brought new inventions such as the electronic start.
The majority of car batteries are 12v. This means that all their electrics have to be efficient to 12 volts i.e. all the bulbs must be a 12v rating so that they are compatible with the car. However with all of these different things being done by the battery it means that it has to recharge in some way otherwise it would only be good for a short while. This is where the alternator of the vehicle comes in because as the engine is running it maintains a charge on the battery. If a battery runs out of charge completely then it will need to be recharged. The most common ways o doing this is to either stick the battery on a mains charger or to jump start the car that the battery is in and leave it running for a while so that the engine charges the battery. Even though it is possible to recharge the batteries sometimes they are still to far gone to ever be good again and this is when you need to look into buying a new charged battery. For a new battery you can pay anywhere between £50 - £100 depending on the size and the vehicle it is going into.