See If A Completely Dead Battery Can Be Recharged

A completely dead battery can be recharged but the process demands extra work, unlike the default (alternator) charging process for a healthy battery. Most car batteries need about 12.2V to 12.8V to power their engine. 

When the voltage of a battery goes below these levels or at most (12V), such a battery is considered completely dead. In other words, the term “completely dead” does not mean the battery is totally hopeless.

To revive or recharge such a battery, you need to jump-start it and this process will require the help of another car’s (healthy) battery.

In this guide, I will be walking you through the 2 common ways to recharge a completely dead battery and how long each process takes. 

You will also be learning about the various scenarios that can quickly drain a car battery and indicators of a dead battery.

What Drains a Car Battery?

A car battery may become flat or completely down due to several reasons. Common ones include:

1. Parasitic drain

This occurs when the lights or other electrical components in your car are running despite switching off the ignition. Parasitic drain is a slow but effective killer of batteries.

2. Faulty alternator

A defective alternator can drain a battery quickly if the voltage it produces is insufficient or the diodes are faulty. 

3. Adverse weather 

Anything above 100°C or below 10°C is bad for car batteries. Exposing them to such conditions gives room for sulfation, which often reduces their lifespan. 

4. Age of battery 

Also, if your battery is old, it may have lost its power to retain a charge effectively. Hence, it drains rapidly. The ideal lifespan of a car battery is about 4-5 years.

How to Safely Recharge a Completely Dead Battery


A dead car battery can be recharged with the help of a battery charger or a jump-start cable.

Battery charger

Then the use of a battery charger is slower and usually requires up to 12 to 15 hours to fully charge your car. This option requires you to plug the battery charger into a socket and connect it to the battery terminals.

People rarely opt for battery chargers because they are not as fast as jump-start cables. They are most suitable for spare batteries or non-emergency situations.


A jump-starter, on the other hand, is a quicker (5 minutes) and safer way to recharge a completely dead car battery. However, the process requires the help of another car with a functional or healthy battery.

Here is how to jump-start a dead car battery:

1. Turn off the engine of the functional car

The first step to jump-starting a car battery is to ensure the functional car’s ignition is turned off. In fact, it is best to turn off both cars.

Failure to turn off the functional car’s engine may result in an electrical surge and damage to electrical components.

2. Connect the positive jumper cable appropriately

The color of a positive jumper cable is red and it has two ends. One end must first be connected to the positive terminal of the dead battery. The other end goes to the positive terminal of the functional battery.

3. Connect the negative jumper cable appropriately

The color of a negative jumper cable is black. After connecting the positive ends appropriately, you must connect the negative ends of the cable.

To do this, one end of the cable must connect with the negative terminal of the charged battery while the other end connects with the car’s grounded (pure or unpainted) metal component (not the negative terminal of the dead battery).

4. Turn the ignition for the functional car

After properly linking the dead and functional battery with a jumper cable, you must turn on the functional car and let it run for about 3 to 5 minutes. This will help the dead or flat battery to gain some juice.

5. Start the completely dead car

To confirm if your dead battery now has some juice, you must try to start the car. If it responds, it means the jumper cables have supplied enough power. If not, allow it to charge a bit longer.

6. Disconnect the jumper cables

Once the dead battery or car is now alive, all you need to do is disconnect the jumper cables from both cars. Ensure you start with the negative jumper cable before moving on to the positive end. 

7. Drive the car for at least 20 minutes

After a successful jump-starting operation and a proper disconnection of the jump cable, you must drive the car for at least 20 minutes. This practice allows the alternator to add extra juice to your car’s battery.

What are the Signs of a Dead Car Battery?

When a battery is dead or is becoming extremely weak, these are the signals to watch out for:

1. Dim headlights

This is the most common sign of a dead battery. When a battery is dead, it loses its charge and will fail to power headlights. Even if it does, the brightness of such a headlight will be very dim or dull.

2. Check Engine Light on

Check Engine Light is a warning signal for a variety of car issues – not just for a dead battery. Nevertheless, it should pop up on your dashboard if your car’s battery is dead.

3. Backfiring

When the battery in your car is weak or dead, your fuel cylinder will experience intermittent sparks, which often result in fuel accumulation. Hence, when you turn on your car’s ignition, fuel burns at a rapid rate and causes backfiring.

4. Slow-cranking engine

Dead car batteries do not have enough power to supply your car’s engine. This may result in a prolonged cranking sound within the engine.

5. Car starts but dies instantly 

When your car starts but dies a few seconds later, it means there is not enough charge in it to keep your car running for a long time. In other words, it is dead or extremely weak.

6. An odd smell

A healthy and functional battery does not smell. However, when it is dead you may sense a strange smell coming from such a battery. 

How Many Times Can a Car Battery be Recharged?

There is no limit to how long you can recharge a dead car battery. The only time a car battery cannot be recharged is when it is completely dead. 

This is why it is best to go for quality brands. They tend to have longer-lasting batteries than average manufacturers.


Can a battery be too dead to jump?

It is very rare to encounter a battery too dead to be jump-started.

When this happens, it may be because your car’s alternator is faulty or the battery is severely damaged.

Why would a car be completely dead?

A car can be completely dead due to a dead battery, loose or rusty cables, and a faulty starter or alternator.

Why don’t you connect the negative when jumping a car?

When you connect the negative end of a jump-start cable with the negative (–) terminal of a dead battery, you risk an explosion.

The right way is to link it to an unpainted metal component of the car or follow the instructions from the manufacturer.

Final Thoughts

A completely dead car battery can be recharged by jump-starting or a battery charger. Jump-starting is the quickest and most reliable option.

Battery chargers, on the other hand, are slower and best for people with spare batteries. As a car owner, you should be able to use both methods to recharge a dead battery.

In cases where your battery fails to be recharged by either a charger or a jump-start cable, I advise you to consult a battery specialist on the next course of action. Such a battery probably needs a replacement.

Also, the positive terminal of a battery is crucial to jump-starting any car and there are various ways you can identify the positive end of a battery.

I hope you found this guide insightful. Thanks for reading.