Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsBattery Diagnosis and ServiceEasy
A technician is performing a battery maintenance check. They notice a white, powdery substance accumulating around the battery terminals. What is this substance, and what does it indicate?
- ACorrosion (lead sulfate, copper sulfate), indicating poor terminal connections or acid leakage.
- BLead sulfate, indicating an undercharged battery.
- CElectrolyte residue, indicating normal battery operation.
- DSulfuric acid, indicating an overcharged battery.
Show answer & explanationAnswer & explanation
Correct answer: A. Corrosion (lead sulfate, copper sulfate), indicating poor terminal connections or acid leakage.
The white, powdery substance around battery terminals is corrosion, typically a mixture of lead sulfate and copper sulfate. This is commonly caused by acid fumes escaping the battery and reacting with the terminal metals, or by a small leak of electrolyte. It indicates poor connection, potential resistance, and a need for cleaning.
Why the other options are wrong
- B. Lead sulfate forms internally during discharge; external white powder is corrosion.
- C. Electrolyte residue is not a white powdery substance, and this accumulation is not normal operation.
- D. While sulfuric acid is in the battery, the white powder is the result of its reaction, not pure acid.
Battery Terminal Corrosion
The buildup of crystalline or powdery substances (typically sulfates) on battery terminals and cables, often caused by acid fumes or electrolyte leakage, leading to increased resistance.
- Often white or bluish-green
- Caused by acid fumes reacting with metal
- Increases electrical resistance
- Should be cleaned with a wire brush and baking soda solution
Memory trick: White powder means bad connection, time to clean and protect.