There are Four stages in the discharging-charging cycle:
1. Fully Charged:
* Positive plate covered with lead oxide (PbO2).
* Negative plate covered with sponge lead (Pb).
* Electrolyte contains water (H2O) and sulfuric acid (H2SO4).
* Current flows in the cell from the negative to the positive plates.
* Electrolyte separate into hydrogen (H2) and Sulfate (SO4).
* The free sulfate combines with the lead (both lead oxide and sponge lead) and becomes lead sulfate (PbSO4).
* The free hydrogen and oxygen combine to form more water, diluting the electrolyte.
3. Fully Discharged:
* Both plates are fully sulfated.
* Electrolyte is diluted to mostly water.
* Reverses the chemical reaction that took place during discharging.
* Sulfate (SO4) leaves the positive and negative plates and combines with hydrogen (H2) to become sulfuric acid (H2SO4).
* Hydrogen bubbles form at the negative plates; oxygen appears at the positive plates.
* Free oxygen(O2) combines with lead (Pb) at the positive plate to become lead oxide (PbO2).
Precautions for Battery: Take the following precautions when working with automotive batteries:
# Wear gloves and safety glasses.
# Never use spark-producing tools near the battery.
# Never lay any tools on the battery.
# If it necessary to remove the battery cables, always remove the ground first.
# When connecting battery cables, always connect the ground cable last.
# Do not use the battery ground terminal when checking for ignition spark.
# Take care not to spill electrolyte into your eyes, onto your skin, and onto any part of the vehicle.
# If you mix electrolyte, pour the acid into the water (not the water into the acid).
# Always follow the recommended procedure for battery testing, charging, and for connecting jumper cables between two batteries.