It happens more often than not especially after replacing a dead or damaged car battery that the battery terminals can disconnect as you drive.
What then happens should the terminals disconnect?
And what can you do to fix them? Read on to find out more.
What Happens if a Battery Disconnects While Driving
Battery Warning Light ON
Should one or both terminals of the car battery disconnect as you drive, expect to see the battery warning light ON.
Car Engine may Die
Additionally, the car engine may die if the alternator cannot supply enough power to the car’s electrical system in case of a failing alternator.
Or, if any appliances that have a heavy power draw are switched ON and the car battery would otherwise be expected to meet the power deficit.
Note, the car battery is only required to start the car. Once the engine is running, its job is to supplement the power needs of the car if case the alternator cannot meet the all power needs of the car.
Why the Car Battery Terminals May Disconnect as you Drive (+Fixes!)
If the battery terminals disconnect as you drive, it may be because:
1. There’s a build-up of corrosion between the battery terminals and battery posts which then interrupts the connection between the terminals and posts reducing or stopping the flow of battery from the battery.
Fix: Remove the corrosion by following the steps listed below
Safety: Important that you wear a face mask and safety goggles
The car engine should be switched off!
- Disconnect the battery terminals from the battery posts. Use a wire brush or an abrasive like light sandpaper to scrub the battery posts and terminals clear of corrosion
- Then firmly connect the battery terminals to the posts so that they make firm clean contact.
- Lastly, apply the grease over the battery post and clamp connection. The grease forms a protective shield to keep out the moisture and any electrolyte from getting into contact with the clamps that would otherwise trigger corrosion!
2. The battery terminals are loose. Check if the battery terminals are tight and firm by gently wiggling the terminals.
They should be tight. If they easily move from side to side or can be lifted off the battery posts then they need to tighten them.
Fix: Tighten the battery terminals. Make sure they do not wiggle from side to side.
You may have to install battery shims or battery sleeves over the loosely fitting battery terminals should they be oversized to make a firm connection.
3. The Battery cables may be cut, or frayed. Inspect both the positive and negative battery terminals along their length for damage.
Cables can be damaged by rodents, age, and prolonged exposure to heat and moisture.
Fix: Replace any damaged cables with others of the same type and gauge.
Related posts: 5 signs that the battery terminals are loose and how to fix them
What Shows a Car Battery is Disconnected (While Driving)
While this is not necessarily a confirmation that the car battery terminal(s) has been disconnected, expect to see the battery warning light ON.
If you’re wondering why it is not confirmation, it is because the light may also come ON in case:
- the battery is dead and not charging,
- the alternator is disconnected or faulty
- the car engine may also die in some cases in case the alternator is not able to supply enough power to the car’s electrical system
Note that in some cases you may still be able to continue driving (but with the battery light ON).
You may also be interested in this post: How long a car battery lasts when disconnected?
Why Disconnecting the Car Battery when the Engine is Running is a Bad Idea
Do not disconnect the car battery terminals while the car engine is running!
Doing so risks damaging the car alternator from the voltage spikes that may be generated when you do so.
Instead, switch off the engine first then disconnect the battery.
Related Posts
Why a Car Engine may Die when the Battery disconnected
If the car engine dies when the battery terminals are disconnected it’s probably because the alternator cannot supply enough power to meet the car’s electrical system requirements.
The alternator may be faulty or undersized for the electrical accessories that are switched on.
Closing Thoughts
Should the car battery terminals become disconnected as you drive, expect to see the battery warning light on the dashboard coming ON.
The car engine may also die if the alternator cannot meet the power needs of the electrical accessories!
