Yes, an internal short circuit in a lead-acid battery can absolutely damage a car. The primary risk isn't an explosion, but a persistent parasitic drain that can lead to a dead battery, strain the alternator, and potentially cause expensive damage to the vehicle's sensitive electronic control units (ECUs). An internal short occurs when the insulating separators between the positive and negative plates inside the battery degrade, allowing current to flow where it shouldn't. This creates a constant internal drain, even when the car is off.
The most immediate symptom is a battery that won't hold a charge. You might jump-start the car, but it will die again shortly after being turned off. This constant discharging and charging puts extreme stress on the vehicle's alternator, forcing it to work overtime to try and recharge a fundamentally faulty battery. Overworking the alternator can lead to premature failure, a costly repair.
The more significant and expensive risk is to the car's electronics. Modern vehicles rely on a stable voltage supply (typically around 12-14.5 volts). A failing battery with an internal short can cause voltage to fluctuate wildly or drop too low. Sensitive components like the Engine Control Module (ECU), infotainment system, and various sensors can be damaged by these irregular voltage spikes and drops. The cost of replacing an ECU can far exceed the cost of a new battery.
| Symptom/Observation | Potential Consequence | Recommended Action |
|---|
| Battery dies repeatedly overnight | Parasitic drain from internal short | Test battery; replace if faulty |
| Alternator becomes very hot, whines | Overworked from constant recharging | Inspect alternator and battery |
| Electronic glitches (flickering lights, error codes) | Unstable voltage damaging ECUs | Immediate battery testing/replacement |
| Battery case feels warm or bulges | Severe internal short generating heat | Disconnect battery immediately; replace |
| Rotten egg (sulfur) smell | Electrolyte boiling due to overcharging | Check charging system and battery |
If you suspect an internal short, the safest action is to stop driving the vehicle and have the battery professionally tested. Replacing a faulty battery is a relatively inexpensive preventative measure against much more severe electrical damage.
