If you test your battery and find that it is not performing as it should be then you will need to replace your battery. This is not as big a job as it sounds and it is definitely possible to do it yourself, as long as you are very careful. Faulty batteries can be very dangerous for a number of different reasons. The acid inside them is extremely corrosive and if there are any leaks it can do a lot of damage. Electricity itself is very powerful and if you connect the wrong wires to the wrong connection points then you could end up seriously injuring yourself or seriously damaging your vehicle.