Hi guys, today we will learn the mystery in the vehicle battery box. We know the battery can store and discharge electric current.
The question is, how does the battery do that?
Evidently, there are chemical reactions that occurs when battery charge and discharge.
We will discuss it
Chemical reactions inside the car battery
For clarity, I will briefly discuss how the battery works from the start.
Battery consists of three main components. Cathodes, anodes, and solutions.
The cathode is a positive plate made of PbO2, while the anode is a negative plate made of Pb.
The two plates are placed in a reservoir that is close together but not attached. Then, the solutions are poured into the reservoir so that both plates are drowned by the solutions.
The solutions we use are H2SO4 solutions or commonly known as sulfuric acid.
Then how is the process going?
The chemical reaction in the battery will automatically run when the anode and cathode are connected. So the cathode will be connected to the positive terminal of the battery, while the anode will be connected to the negative terminal of the battery.
And if we make a series of lights, then the chemical reaction in the battery will run when the light switch is activated.
When the light circuit is connected, it will connect the positive terminal of the battery to the negative terminal of the battery, so that the chemical reaction can take place.
The reaction, sulfuric acid will break down into hydrogen and sulfur. Then, sulfur will stick to the anode, so that the anode plate becomes PbSO4.
H2SO4 + Pb ---- H2 + PbSO4 (Pb plate receives charge)
Then, hydrogen ions will absorb oxygen on the cathode plate made of PbO2 plate.
H2SO4 + PbO2 ---- H2O + Pb (Pb plate releases charge)
So, this reaction will convert the sulfuric acid into pure water, but this is only the effect of the reaction and not what causes an electric current to flow.
The thing that causes the electric current to flow is on both plates.
If you see the two reactions above, in the first reaction the Pb plate (anode) receives a charge while in the second reaction the Pb plate (cathode) releases the charge. This activity causes a potential difference between the anode and cathode. This potential difference makes electricity flow.
Then how is the reaction when the charging process is carried out?
As I said above, the discharging reaction will convert the sulfuric acid solution into pure water. And when that happens, chemical reactions can no longer run so that the battery does not generate electric current.
In this condition, it can be said that the battery is empty and needs to be recharge.
The recharge process will reverse the reaction. And the trigger, the anode and cathode plates must be connected to the current source.
So when the cathode plate gets an electric current, it breaks down water molecules into hydrogen and oxygen. Oxygen will be attracted to the cathode plate so that it returns to PbO2.
Pb + H2O ---- PbO2 + H
Then on the anode plate, the electric current on the anode plate will break down the sulfate molecules on the anode plate. So that the anode plate returns to Pb, and the sulfate that is released will immediately combine with the hydrogen ion. So that the sulfuric acid solution is formed again.
PbSO4 + H ---- Pb + H2SO4
The end result of this recharge process will return to normal condition. So that the discharging reaction can be carried out again.
That's an explanation of how the chemical reaction in a vehicle battery.