What Happens if Car Battery Disconnects While Driving?

While for the most part of your driving the car battery cables will stay connected to the battery, there can be that odd time when one or both of the terminals disconnect from the battery.

Should this happen, you’d probably want to know if it has affected the functioning of the car in any way and possibly, what you can do in the future to prevent a repeat of cables disconnecting.

Keep reading to learn what can happen should the battery cables disconnect while driving, how you may be able to tell that the battery cables are off as you drive, and also what happens when the car battery dies as you drive so that you are better prepared should it happen to you.

Signs the Car Battery is Not Connected (While Driving)

If the car battery disconnects while driving, you should expect to see the battery light ON (and staying on) on the car’s dashboard signaling there is a problem with the car’s charging system.

Unfortunately, this can point to several causes including loose connections, a dead battery, or a bad or disconnected alternator.

In addition, you encounter either of the two scenarios:

#1. You are able to continue driving as the car alternator is able to meet the power requirements of the car.

#2. The car engine stops. This happens when the alternator is not able to meet the power requirements of the car’s electrical system.

This may be because of a faulty alternator, weak cable connections, or even as a result of excess demand from the car accessories.

So, while the car can stop sometimes, know that in some cases you may be able to continue driving (but with the battery light on).

You may also be interested in this post: How long the car battery lasts when disconnected?

Common Causes of Loose Battery Cables (+Fixes!)

A weak, loose, or disconnected cable connection can interrupt the current flow to and from the car battery.

The car battery cables can disconnect while driving for several reasons.

Here are a few places you can check (listed in order of simplest to check).

#1. Conduct a visual inspection of the connections between the battery terminals and battery posts for any signs of corrosion.

This is the bluish-yellow powdery substance that forms around the battery posts.

As corrosion builds up, it interferes with the connection between the terminals and posts in effect weakening it.

Fix: Remove any corrosion buildup by following the steps below and then apply dielectric grease.

Steps to Remove Battery Corrosion

Safety: wear a face mask and safety goggles

  • Clean the battery posts and battery terminals with a wire brush or an abrasive like light sandpaper or other to remove rust or any traces of corrosion.

This is where the mask and safety goggles come in handy.

  • Firmly connect the battery clamps to the posts so that they make firm clean contact.
  • Lastly, apply the grease over the battery post and clamp connection, like a protective shield to keep out the moisture and any electrolyte from getting into contact with the clamps.

#2. Loose battery terminals. Check if the battery terminals are tight and firm.

Gently wiggle the terminals. They should be tight. If they can be moved easily then they are not be making the required firm contact for good current flow. Therefore tighten them.

Fix: Tighten any cable connections. Consider installing battery shims or battery sleeves on top of loosely fitting battery terminals to make a secure connection.

#3. Damaged battery cables. Check the battery cables including the ground cable along their length up to where they connect. Gently wiggling them while checking for fraying or other signs of damage. Cables can be damaged by rodents, age and prolonged exposure to heat and moisture.

Fix: If there any damaged cables, replace them with cables of the same type and gauge.

Related posts: 5 signs that the battery terminals are loose and how to fix them

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What Happens when a Car Battery Dies While Driving?

The car battery light will likely show. The engine will continue running provided the alternator is able to meet the electrical needs of the car – headlights, heater and what ever is switched on. Should the demands on the alternator exceed what it is able to supply, then the car engine will stop.

Note that the battery is only required when the car is starting and therefeafter supplements the power needs of the car if the alternator cannot meet the all power needs of the car.

Should You Disconnect the Car Battery while the Engine is Running?

No, you shouldn’t. Disconnecting the battery while the engine is running can lead to voltage spikes in the alternator that can damage it. To avoid risk of damage to the alternator, switch off the engine first before you disconnect the battery.

Final Word

The disconnection of battery cables as you drive does not necessarily result in the engine stopping. If the alternator is able to meet the power requirement of the car, then the engine will continue running until you switch it off or the power demands of the car cannot be meet by the alternator.

Do not disconnect the battery as the engine runs as this risks damage to the alternator. Always switch the engine off first.

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