can you jump a car witha bad battery

[OAustin]

Yes, you can jump-start a car with a bad battery, but it is strictly a temporary fix to get the vehicle to a repair shop. A "bad" battery typically means it cannot hold a charge. Jump-starting provides the necessary power from a donor car to crank the engine. Once running, the alternator takes over, powering the car's systems. However, if the battery is truly degraded, it will not recharge properly and the car will likely stall once you turn it off again. This procedure is for moving the car, not fixing the underlying problem.

The key is determining if the battery is just discharged or has failed internally. Extreme age (over 5 years), visible damage like a bulging case, or a sulfur (rotten egg) smell indicate a bad battery that needs replacement.

Step-by-Step Jump-Start Guide:

1. Position Vehicles: Park the donor car close to yours, engine off, without the cars touching.
2. Connect Red Clamps: Attach one red (positive) clamp to the dead battery's positive terminal (+). Connect the other red clamp to the donor battery's positive terminal.
3. Connect Black Clamps: Attach one black (negative) clamp to the donor battery's negative terminal (-). Crucially, attach the final black clamp to an unpainted metal surface on the dead car's engine block or chassis, not the negative battery terminal. This minimizes the risk of sparking near battery gases.
4. Start Donor Car: Start the engine of the donor car and let it run for a few minutes.
5. Attempt Start: Try to start the car with the dead battery. If it starts, let both cars run connected for a few more minutes.
6. Disconnect in Reverse Order: Carefully disconnect the cables in the exact reverse order: black clamp from the dead car's metal, black from donor battery, red from donor battery, red from once-dead battery.

Important Considerations:

• Safety First: Always wear safety glasses. A failed battery can leak explosive hydrogen gas. Any spark can cause an explosion.
• Modern Vehicles: Complex electronics in modern cars can be sensitive to voltage spikes. Using a modern car as a donor is generally safe if done correctly, but a portable jump starter pack is often a safer, recommended alternative.
• Drive Immediately: After a successful jump, drive the car for at least 20-30 minutes to allow the alternator to recharge the battery. If the battery is bad, this will not work, and the car will die again once stopped.

Common Battery Failure Indicators	Typical Symptom	Recommended Action
Age	Battery is over 4-5 years old	Preemptive testing or replacement
Slow Cranking	Engine turns over very slowly or makes a clicking sound	Jump-start possible, but battery likely needs replacement
Electrical Issues	Lights dim significantly when trying to start	Indicates battery cannot provide sufficient current
Visible Damage	Corroded terminals, bulging or cracked case	Do not jump-start; replace battery immediately
Swelling/Smell	Battery case is swollen or emits a rotten egg smell	Do not jump-start; battery is damaged and potentially hazardous

[DeMaria]

You can, but don't expect it to last. Think of it like giving a dead phone just enough juice to turn on for a minute. The goal is to get it to a mechanic, not to run errands. Hook up the cables correctly—positive to positive, and the last negative clamp to a bare metal spot on your car's frame, not the dead battery. Once it starts, drive straight to an auto parts store. They can test the battery for free and tell you if it's truly shot, which it probably is.

[DelRichard]

My dad, a mechanic for 40 years, always warned me about this. Jump-starting a bad battery is a band-aid, and a risky one. The main danger is the battery itself. If it's damaged, it can release hydrogen gas, which is highly flammable. A single spark from connecting the cables wrong could cause it to explode. That's why you always connect the final negative cable to the car's chassis, away from the battery. If you're not 100% confident, it's safer and cheaper in the long run to just call for a tow or roadside assistance.