Can a Battery Drain with The Negative Cable Disconnected?

Hi, I'm Luis Johnson, an automobile technician, and power equipment professional. By profession, I'm a businessman and operate a car workshop. I have created this...Read more

One popular way to prevent battery drainage is to disconnect the negative cable. But, many car owners still notice battery drainage after doing that. And, that’s not even a rare case. So, what’s the reason behind it? Can a battery drain with the negative cable disconnected?

In general, No, battery drainage shouldn’t happen after you have disconnected the negative cable. But, there are some exceptions to this rule. If the battery is too old, contains a damaged electric system, or even due to a parasitic draw, you will notice battery drainage.

In this article, we have analyzed the issue in detail. Apart from that, we will also explain the consequences if you disconnect the negative cable and how to stop battery drainage in your car successfully.

Sounds useful? Then, keep reading.

Can a Battery Drain with The Negative Cable Disconnected?

A battery shouldn’t drain if you have disconnected the negative cable. Because both positive and negative terminals create a circuit for the electricity to flow smoothly.

Can a Battery Drain with The Negative Cable Disconnected

If you can break the circuit in any way, it would block the path. As a result, the battery stays on its own without any connection to the ground or any other system.

So, How Does the Negative Cable Work?

Suppose you want to jump-start the dead battery again. For that, you need to connect one end of the dead battery’s negative cable to the other one’s negative side. As for the other end, ground it properly. Now, disconnect the negative cable keeping everything else untouched.

You will notice that the battery isn’t starting anymore. That’s what we are trying to explain. Cutting the negative cable would stop any transfer of electricity.

You can disconnect the cable to avoid losing battery charge as well. Because there is no available path for transferring it.

Why Does the Battery Drain with The Negative Cable Disconnected?

If the battery was charged beforehand, it should remain like this until you run the vehicle again. But the battery might discharge itself even after the disconnection. Why does it happen? Here’s your answer.

Parasitic Draw

Your car’s parasites are the objects that draw electricity from the battery after the engine stops. Once your car’s engine is shut off, there are some objects like interior lights, radio, automatic seat adjustment, etc.

All these items remain in the sand-by mode and keep discharging the battery. It might occur even after you have removed the negative terminal.

Wear Out/ Damage

If your battery is not working as it should, it might’ve worn out. If you have not changed the battery for a long time, that could be the real issue. You have to replace the battery immediately to get rid of this problem.

Why Does My Battery Drain Even When Not in Use?

Batteries discharge in two ways: directly or indirectly. When you are using the car, the battery charge will keep draining. That makes sense. But, even when it’s not in use, the battery can self-drain. There are several factors that work here.

Unusual Temperature

Car batteries contain a liquid chemical (lead) inside. And, these substances are vulnerable to changes in temperature. When it’s too hot or too cold, the density of these chemicals can deteriorate. That’s why, even though your battery might drain even if it’s parked.

Car Settings

If your car has seat memory, a connected computer, an alarm system, etc., the battery will die sooner. Even if you are not using any of these features, the battery requires energy to keep the car in standby mode. So that, anytime you decide to drive, it can automatically run those features smoothly.


If you haven’t charged the battery 100%, it will start discharging itself. When you bring the car home for the first time, the alternator is at its highest charging capacity.

But, as it gets older, it becomes less efficient. That’s the reason, even when the reader says “fully charged or 100%” it still requires more time to be full. Since most people don’t know about this issue, their batteries stay half-charged in the garage.

Another big problem is that not every battery has the same chemicals. Some have Nickels, while some use lithium Ions. For the former ones, not charging the battery to its fullest won’t be an issue. However, it’s a grave mistake if your car has the latter battery type.

You May Also Read: Do You Have To Replace Battery When Replacing Alternator?

What Are Some Best Ways to Stop Battery Drain?

Now that you have understood the reasons behind battery drainage, let’s try to solve them. Here, we have listed some effective and easy hacks for you.

What Are Some Best Ways to Stop Battery Drain

Charge It Fully

We have already mentioned what happens to a half-charged battery. It dies. If you want to avoid that make sure the unit is 100% charged before leaving the garage.

But, how can you be sure about that? You can run a voltage test for that. If the result is anything below 12.6V, you need to charge more.

Here, we would like to address a common misconception. People assume 12.0V is the maximum limit. But, the truth is, if you level the battery at this level, it will be considered half-charged. So, make sure it reaches 12.6V.

Disconnect the Negative Cable

Even if it sounds a little tough, you should disconnect the negative cable. It’s a good practice if you want to avoid battery drainage. To be honest, disconnecting any terminal would do the trick.

However, experts consider the positive side of being quite risky. That’s why we will suggest you disconnect the negative cable only. It has a connection to the chassis or ground.

That’s why, even when the car is not in use, the battery power keeps draining. Cutting this connection will help the battery store more power.

Refill the Electrolytes

The electrolyte level inside the batteries doesn’t remain constant. The original density or ratio changes because of weather or age. As a result, your car’s battery remains weak even after a full charge. We have already mentioned the importance of a full charge to stop battery drainage.

In that case, you have to refill the electrolytes and make the battery power again. But here’s a catch. You must know the right solution for the battery along with the ratio. And, to check the level of the electrolytes, try using a hydrometer.

Regular Maintenance

Regular maintenance is the key here. If the weather is too cold, try to keep the car inside a shelter. Regularly clean the battery to avoid damage caused by the debris.


Got more queries regarding a draining battery? No worries. We have prepared this FAQ section specially to answer your most asked questions. Have a look.

What Happens if I Remove the Positive Terminal First?

If you remove the positive terminal first, there are chances of short-circuit or even a blast. That’s because the wrench you use for cutting the connection is made of metal. It has the potential to draw a lot of current during the process.

By chance, if you let the wrench touch any part of the car or even your ring, the output can be pretty dangerous. That’s why experts always recommend disconnecting the negative terminal first.

What Happens if You Connect Car Battery in Wrong Order?

If you connect the car battery in the wrong order, the unit won’t start. That’s all. If you end up joining the positive cables into the negative side, the current won’t be able to pass.

Since the electricity won’t reach the battery, there’s no way you can drive the vehicle. But it’s not dangerous at all. You can just change the order afterward.

What Happens if You Disconnect a Negative Terminal While a Car Is Running?

You can’t disconnect a negative terminal while the car is running. Because, if you manage to cut the negative cable, the vehicle will automatically come to a halt. It might use the remaining battery charge to run for a while. But soon your battery will be dead.

Why Should You Disconnect the Negative Terminal First?

You must disconnect the negative terminal first, because of your safety. As you know, one end of the negative cable goes into the chassis. When you are cutting the connection, your wrench has a high chance of touching that chassis.

For a negative cable, it’s perfectly safe. However, if you try the same thing with a positive cable first, be ready to face an explosion.


Battery drainage is really frustrating. Especially, when you have filled the battery with 100% charge. However, there are just certain factors that are out of our hands. For example, weather temperature, battery type, etc.

We should rather focus on the things that we can change. And, the first thing on this list is disconnecting the negative cable after charging the battery. This extra layer of precaution will save you a lot of time when you need an urgent ride.

Hopefully, you have found the information you were looking for.

Hi, I'm Luis Johnson, an automobile technician, and power equipment professional. By profession, I'm a businessman and operate a car workshop. I have created this site Batteryquery to help people purchase the right battery for their vehicles. The reason behind creating this site is to help my customers purchase the right car battery who often purchase the wrong one due to their lack of knowledge.

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