ASE G1 Auto Maintenance and Light RepairElectrical/Electronic SystemsEasy
A technician is diagnosing a vehicle with a completely discharged battery. After charging the battery, they perform a battery load test and the battery voltage drops to 9.0 volts while cranking, and the CCA rating is significantly below specifications. What is the MOST likely cause of this condition?
- ALoose or corroded battery cable connections.
- BAn internally shorted or sulfated battery.
- CExcessive resistance in the starter motor circuit.
- DA faulty voltage regulator in the charging system.
Show answer & explanationAnswer & explanation
Correct answer: B. An internally shorted or sulfated battery.
A battery that drops significantly below 9.6 volts during a load test, especially with a low CCA rating, indicates internal damage such as shorted cells or extensive sulfation, preventing it from holding an adequate charge or delivering sufficient current.
Why the other options are wrong
- A. Loose or corroded connections would cause high resistance and voltage drop, but the problem description points to the battery's internal capacity (low CCA, low voltage under load) rather than just connection issues.
- C. Excessive resistance in the starter circuit would primarily affect cranking speed, not necessarily cause a severely low battery voltage reading during a load test if the battery itself were good.
- D. A faulty voltage regulator would primarily affect the charging system's ability to maintain battery charge while the engine is running, not the battery's ability to hold a charge or perform under a load test.
Battery Load Test Interpretation
A battery load test assesses a battery's ability to deliver current under a simulated starting condition.
- Healthy batteries should maintain at least 9.6 volts for 15 seconds during a load test.
- Voltage dropping below 9.6V or significantly reduced CCA indicates internal battery issues.
- Load tests are performed on fully charged batteries.
Memory trick: Voltage drops, CCA flops, battery stops.