No, you should not attempt to charge a car battery that has an internal short circuit. Doing so is ineffective and presents significant safety hazards, including the risk of fire, explosion, or the release of toxic gases. A shorted battery has a permanent internal fault, meaning it can no longer hold a charge or function properly. The electrical energy from a charger cannot fix the physical damage inside the battery and will instead generate excessive heat.
When a battery has an internal short, one or more of its six cells (each providing ~2.1 volts for a total of 12.6V) has failed. This creates a direct path for current to flow inside the battery, bypassing the normal chemical reactions needed for storage. A charger will continuously pump energy into this faulty system, leading to dangerous conditions.
Key Risks of Attempting to Charge a Shorted Battery:
- Thermal Runaway: The battery can overheat rapidly, causing the electrolyte solution (a mix of sulfuric acid and water) to boil. This buildup of pressure can warp the battery case and lead to a rupture.
- Hydrogen Gas Explosion: The charging process produces highly flammable hydrogen gas. A spark from the battery terminals or a nearby source can ignite this gas, causing an explosion.
- Toxic Fumes: An overheating battery can release corrosive sulfuric acid mist and other harmful gases into the air.
How to Identify a Shorted Battery:
The most definitive sign is a voltage reading that will not rise above 10.5 volts, even after attempting a charge. A healthy battery should read around 12.6V when fully charged. A shorted battery may also have a swollen or warped case, feel hot to the touch, or have a distinct rotten egg smell (from sulfur).
| Symptom | Healthy Battery Indicator | Shorted Battery Indicator |
|---|
| Resting Voltage | ~12.6 Volts | Below 10.5 Volts |
| Case Condition | Intact, no swelling | Swollen or warped |
| During Charging | Voltage steadily increases | Voltage remains very low, battery gets hot |
| Smell | No strong odor | Rotten egg smell (hydrogen sulfide) |
The only safe course of action is to discontinue use immediately. Disconnect the battery cables (negative terminal first) and take it to an auto parts store or a certified recycling center for proper disposal and replacement. They can test the battery to confirm the failure and ensure it is handled safely.
