Power-Sonic Sealed Lead Acid Batteries - Technical Manual - Manual (Page 5)

POWER-SONIC Rechargeable Batteries 
Discharge
During the discharge portion of the reaction, lead dioxide (PbO
2
) is converted into lead sulfate (PbSO
4
) at the positive
plate. At the negative plate sponge lead (Pb) is converted to lead sulfate (PbSO
4
). This causes the sulfuric acid (2H
2
SO
4
)
in the electrolyte to be consumed.
Figure : Chemical reaction when a battery is being discharged
Charge
During the recharge phase of the reaction, the cycle is reversed. The lead sulfate (PbSO
4
) and water are
electrochemically converted to lead (Pb), lead dioxide (PbO
4
) and sulfuric acid (2H
2
SO
4
) by an external electrical charging
source.
Figure : Chemical reaction when a battery is being charged
Theory of Operation
The basic electrochemical reaction equation in a lead acid battery can be written as: