All motorists sooner or later find themselves unable to start their own car because of the low battery: but why is it happening and, above all, what is this indispensable part of our car and how does it work?
The batteries of the cars are devices for the accumulation of electrical energy (which occurs through a chemical process) and work in every way like a normal battery. The main part consists of two electrodes or Battery Capacity Electrolyte, one positive and one negative, immersed in an electrolyte (a substance that is divided into ions in solution).
Their purpose is to accumulate electricity and release it in the form of direct current: in our cars the function of the battery is to allow the starter to be started via a small discharge, and to keep the electrical system active.
These batteries, usually constituted by lead Battery Capacity Electrolyte immersed in sulfuric acid diluted in water, are called secondary, that is to say they can be recharged once the charge is exhausted.
When the battery is in operation, a current develops between the electrodes, which over time changes its chemical composition, converting lead into lead sulfate: the latter will eventually cover the negative electrode with a white patina. This phenomenon, called sulfation, can make them unusable in the long run
Fortunately, the car batteries deliver a brief discharge of a few seconds to allow the starter to start, and then they are automatically recharged, while the machine is running, by the dynamo to which they are connected. In theory, therefore, the sulphation process could be avoided, except that we often adopt wrong behaviors, such as keeping the electrical system on for a long time, while the car is not in motion.
Batteries are often damaged as a result of another phenomenon, the so-called self-discharge: in particular, the level of the electrolyte is lowered too much (often due to evaporation), favoring the oxidation and deterioration of the conductors due to a greater concentration of acid. Often in these cases there are short circuits which make them unusable.
As said before, most of the times, fortunately, we can recharge the battery: it will be enough to let it cross by an electric current coming from an external source, a process that will trigger a reverse chemical reaction, bringing back the lead sulfate to its original state.
During the charging process, however, the electricity breaks down the water contained in the electrolyte into hydrogen and oxygen, which will be released in the form of gas: for this reason it is important to often check the level of the liquid in the battery, to avoid the process of self-discharge.