General Knowledge of Batteries
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Chemical Reaction During Charging and Discharge
Charging is a process where the electrolyte’s water turns back into thin sulfuric acid. The specific gravity of the electrolyte and voltage rise to the regulated level. When the battery is fully charged, the specific gravity of the electrolyte and voltage no longer rise. The electric separation of water accelerates, actively generating hydrogen and oxygen. There is active gas generation at the end of charging and when discharging. Hydrogen is explosive and oxygen is flammable, so the battery must be kept away from flame when charging.
When the battery is discharged, the electrolyte is in the form of thin sulfuric acid (H2SO4 + H2O) almost like water. Only sulfuric acid reacts during the chemical reaction and the specific gravity and voltage of the electrolyte decrease. If the discharge continues, the active material turns into lead sulfate (PbSO4), leading to a state of full discharge that can no longer generate electricity. If the battery is over-discharged below a certain voltage, it can cause shock to the battery and a subsequent life-shortening. This is why, in most cases, car batteries are only discharged to 10.5V (1.75V / Cell).