How to Open Locked Car Door with Dead Battery? [Guide]

One of the common mishaps regarding cars is getting locked out of one. It’s never a good feeling when you’re locked out of your car because of a dead battery.

It can be a very troubling situation. All that matters is regaining access to your car through the door. Luckily, we can help you out with solutions.

So, how to open locked car door with dead battery?

Locked car doors with a dead battery can be opened based on the situation. If the FOB battery’s dead, using the mechanical key’s the solution. The FOB battery can also be replaced. On the contrary, if the car battery’s dead, it needs to be jump-started. For that, you’ll need the aid of another car. 

Wait, there’s more. Don’t miss out on the more important details: hacking car locks and reviving dead batteries. Read this till the end-

Does A Dead Battery Affect Power Locks?

A ‘dead’ battery doesn’t convey a good message. And that is entirely true for the power locks inside a car. Your car may be powered by a combustion engine or an electrical engine. In both cases, the battery matters a lot.

There are cases where the manual key won’t unlock the car door because the battery is dead.

Speaking of batteries, there are 2 types. There is of course the car battery. Also, there is a FOB battery that is present in the remote key of the car. Both affect the power lock in different ways. I’ve explained them below, have a look.

Open Locked Car Door with Dead Battery
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If The FOB Battery is Dead

The FOB batteries reside in the key of a car. It’s more common in keyless cars than in regular cars. 

This battery basically powers the key so that it can connect to the central lock system. The Free On Board (FOB) key allows you to unlock car doors remotely. 

When the FOB battery is dead, the key cannot communicate with the car. That’s why the keyless feature stops working. 

Even if the car battery is charged and is good to go, it won’t help. A dead FOB battery basically stops you from remotely unlocking car doors. There are many advantages/disadvantages of manual vs auto lock systems. This is one of them.

If The Car Battery is Dead

There’s a 12-volt battery present in any type of car. The battery helps with the air conditioning of the car, sound system, dome lights, headlights, etc. 

It also provides the locking system with the power it needs. So when the battery is down, the locking system gets affected as well. In these cases, the battery is dead and the car doors won’t open

The car battery powers the whole locking system. As a result, when the car battery runs out, your locking system won’t work. Even the FOB battery won’t be of use in such cases. 

Many people ask, can you unlock your car with a dead battery

The answer is positive and short- yes. You can get access your car in a number of ways even if the battery is dead.

There are 2 situations regarding this. I have mentioned the situations and solutions in the next segment. Keep on reading to find out.

Opening a Locked Car Door with a Dead Battery: 2 Different Situations

There are 2 functional batteries in a car which is the most important. The first one is the battery of the car. It powers the electrical systems of a car. The FOB battery in the key is the second one. 

If either of these batteries is down, unlocking the car door won’t be possible. However, don’t stress because we will back you up! Have a look at the emergency solutions we’ve provided here.

Situation 1: What To Do If The Fob Battery Is Dead?

When the FOB battery runs out of charge, your keyless features will be disabled. But how to unlock a keyless car door without a key? Well, there are 2 possible fixes for it. 

Instant Solution: Use the Mechanical Key

Inside the key FOB, there’s a mechanical key for the car. Many keyless car owners are unaware of this. 

The mechanical key can come in handy in many situations. Quite conveniently, it can provide a solution when the car battery is dead.

Mechanical keys are attached inside the key FOB. Pulling on the tip of the FOB key will bring out the mechanical key. 

In most cases, the mechanical key only works for the driver’s door. So even if the FOB battery runs out of juice, you always have a backup option!

Long Term Solution: Replace the Fob Battery

Another solution for a dead FOB battery is replacing the dead battery with a new one. It is an easy process; here are the steps-

  • First, check for the battery housing in the key FOB. Taking apart the key FOB gently will give you access to it.
  • Secondly, know which type of battery your key FOB uses. Usually, watch batteries are used for FOB keys. A good FOB battery is the Energizer CR2032. The performance of this battery is outstanding!
  • Finally, match the negative and positive terminals and replace the battery. After that, put the key FOB back together and test it out. If the key FOB is not unlocking the car door, flip the battery and try again.

This is how to unlock a smart car with a dead battery. The above information is for the FOB battery. 

In some situations, the car battery might be dead too. Don’t stress though; there are solutions to that as well. Keep reading to unveil the fixes! 

What To Do If The Car Battery Is Dead

Situation 2: What To Do If The Car Battery Is Dead?

A car battery being dead is a very annoying and bad situation. The features that are powered up in the car by batteries are interrupted when the battery is dead. 

This goes for the car door locks as well. The central lock of a car is powered by the car battery. Therefore, it’s unable to function with a dead battery. Though, there are fixes for this.

Solution: Jump Start the Car Battery

The solution for a dead car battery is to jumpstart the battery. Jumpstarting a battery is known to revive a depleted battery. For dead batteries, it can provide a temporary charge. Using that charge you can easily unlock the door.

Here is how you can jumpstart a battery-

  • Firstly, get another car to help you out. The helping car’s battery will help jumpstart the battery on your car. Alternatively, you can take from any vehicle with an engine and a car. Trucks and buses can work too. Park the vehicle against your car and bring the engines to close.
  • Secondly, turn off the power for both vehicles. For safety, you can also give some time to cool the engines off. Car batteries like the Optima OPT8040-218 D35 help the engine cool off even faster.
  • Thirdly, get a pair of jumper cables. Connect the positive cables to the positive terminals of your car’s battery. The second vehicle has to be set up the same way. Be sure you don’t confuse the terminals. Keep in mind, red means positive terminal, and black means negative terminal.

    Many think that you get shocked by car batteries. It actually depends on some factors. As long as you get them right, you don’t have to worry.
  • After that, start the second vehicle’s engine. That will send a short burst of electricity to your car’s battery. Hopefully, it’ll be enough to revive it for some time!
  • Finally, disconnect the positive and negative terminals of the jumper cables safely. That’s all.

How Long Do Batteries Last In Door Lock?

Many people think that car door batteries run out very quickly. However, contrary to popular belief, door lock batteries do last for a long time.

So for example, if you are to make 20 entries each day, the battery might last for 6-8 months. To ensure optimal battery usage, make sure there is no interference in the locking mechanism. The door should be properly aligned as well. 

When the car batteries run out, they need to be replaced. Car batteries do not recharge themselves, only the alternator does it. So if you want a smooth and functional locking system, keep your car door battery charged. 

Try to reduce the idle time you spend on your car to maximize battery life. Open doors can drain the battery pretty quickly. Try closing the door of your car as soon as possible.

Other than doors, many actions may drain the battery and kill battery cells. Dead cells in car batteries occur mainly because of unnecessary car battery usage. This consists of turning on headlights, dome lights, etc without any purpose. 

You can opt-in for heavy-duty batteries such as the Odyssey 34-PC1500T Automotive and LTV Battery. This can prolong the battery cycle so it’ll take much more time to run out!

Does a Dead Battery Affect Central Locking?

Yes, a dead battery does affect the central locking of a car. This is more common in the latest cars, and for a reason. Most of the cars you use and see nowadays have a central locking system. 

This system uses power from the car battery itself. So when the car battery is dead, the central locking system is disconnected from power. For that reason, the system sits idle with a dead car battery and does not work.

Car users have asked If the car battery is dead will keyless entry work. Well, no. The keyless entry only works when the central locking system of your car is up. 

Even if the FOB battery still has charge, it has no connection with the car battery. So if car batteries are bad or dead, the keyless system cannot control the central locking. 

When the car battery drains out, that’s when the central locking system fails. You may be locked outside or locked inside a car with a dead battery for it. In that case, you can utilize the solutions mentioned earlier in this article!


How to Open the Hood of a Car With a Dead Battery?

By accessing the release lever inside the car, you can easily open the hood. This works for any dead battery consisting car. This lever is located near the driver’s seat. The release lever needs to be pushed or pulled; depending on the car model you own. Then pulling on the hood itself will open it.

How to Open the Trunk of a Car With a Dead Battery?

You can easily open the trunk of a car battery by using the trunk release. It will work with dead or disconnected batteries, so don’t worry at all. Through the trunk pass-through, you can access the trunk release handle. It is generally at the rear seat section of a car, but it depends on the model.


Hopefully, we’ve been able to analyze how to open locked car door with dead battery

If you’re facing other problems, you can always hire a professional lockpicker. That way, you can unlock your car door in emergencies.

All the best.