can car run with dead battery

[MacEden]

Yes, a car can run with a dead battery, but only after it has been started by an external power source. Once the engine is running, the vehicle's alternator takes over, generating electricity to power all the car's systems and recharge the battery. The battery's primary job is to provide the massive burst of energy needed to crank the starter motor. After that, it plays a much smaller role.

However, if the battery is completely dead or damaged, it may not hold a charge from the alternator. In this case, the car might run for a short while but could stall once electrical demand exceeds what the alternator can supply alone, especially at idle. A failing alternator would also prevent the car from running for long.

The most common and effective method is a jump-start. This uses jumper cables to connect your dead battery to a good one in another vehicle, providing the necessary power to crank your engine.

Jump-Starting Method	Typical Success Rate	Estimated Time to Recharge Battery While Driving	Key Consideration
Using Jumper Cables	>95%	30 minutes to 1 hour	Correct cable connection is critical to avoid damage.
Using a Portable Jump Starter	~90%	30 minutes to 1 hour	Device must be fully charged beforehand.
Push-Starting (Manual Transmission Only)	~80%	30 minutes to 1 hour	Requires a slope or 1-2 people to push; not possible with automatics.

For a long-term solution, you should drive the car for a sustained period (at least 30 minutes of highway driving is best) to allow the alternator to recharge the battery. If the battery dies again soon after, it's likely old and needs replacement, or there could be a problem with the alternator or a parasitic drain drawing power when the car is off.

[DeGideon]

If you've got a standard automatic, you're gonna need a jump. Hook up those cables to a friend's car or a portable jump pack, and you'll be back in business in a few minutes. Once it's running, don't just turn it off right away—drive around for a good half-hour so the alternator can put some charge back into the battery. If it's a stick shift, you might be able to get it going by pushing it and popping the clutch, but that's a bit of a hassle.

[PaisleeLee]

As a mechanic, I see this often. The key is understanding the system. The battery starts the car; the alternator keeps it running. A jump-start provides the initial crank. Once running, the vehicle should operate normally if the alternator is healthy. However, a battery that repeatedly dies indicates it can no longer hold a charge or there's an underlying electrical fault. A simple voltage test can determine if the battery needs replacement or if the alternator's output is insufficient.

[SerenityFitz]

I had this happen in a parking lot last winter. I used a compact lithium jump starter I keep in my glove box—it was a lifesaver and didn't require another car. I let my engine run for about 40 minutes while I did some errands. The car was fine for the rest of the day, but the battery died again the next morning. That was the sign I needed; I drove straight to the auto parts store for a new battery. It’s a good idea to test your battery’s health proactively, especially before cold weather hits.