Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Design and function: Discharge
The process during discharge
- Negative plate: Pure lead is converted to lead sulfate
- Electrolyte: The sulfuric acid is converted to water
- Positive plate: Lead oxide is converted to lead sulfate
- Power consuming components.
During discharge, the lead in the negative plate is converted to lead sulfate (PbSO4 ).
The lead dioxide (PbO2 ) in the positive plate is also converted to lead sulfate. During the discharge process, sulfuric acid (H2 SO4 ) is consumed while water (H2 O) is created. This reduces the density of the electrolyte.
The density drops throughout the discharge process and can be gauged to determine the condition of the battery. The electrolyte in a fully charged battery has a density of 1.28 g/cm3 . The density of the electrolyte in a fully discharged battery is 1.10 g/cm3 .
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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