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If you do not want to lose the car memory settings such as (seat, mirror position, or radio station presets) when changing the car battery then you might be tempted to swap the old with the new while the engine is running.
After all, you may argue, the alternator can keep the car’s electricals powered while you change the battery, right?
The question is – Is it a safe way to do it? What are the dangers and how else can you keep the car memory settings – seats, mirrors, station presets safely and easily?
If you’re in this situation and do not know what to do then read on to find out why it is not advisable to swap batteries while the car engine runs and for tips to save the memory settings.
Why You Shouldn’t Swap a Car Battery with the Engine Still Running
Here’s why:
1. The Car Alternator and The ECU – Car Computer may be Damaged
Doing so risks damage to the car alternator and the ECU – car computer. The surge in the alternator voltage output when you disconnect the battery with the engine running has damaged many alternators and the car computer!
In the case of the alternator, it’s usually the rectifier diodes that blow and need to be replaced.
All in all, you will have to invest in a replacement alternator and possibly labor too unless you have the skills to replace the alternator safely!
2. There’s a higher likelihood of Shorts and Arcing
Swapping batteries while the car engine is running increases the likelihood of a short.
Now you have to deal with a hot alternator positive cable too.
Can you Change a Car Battery while the Engine is Running Though?
Yes, you can but it is not recommended. You can easily damage the car alternator or the car computer if you do this.
Will a Car Engine Run without a Battery Connected?
While a car engine can run when a battery is not connected provided the alternator is in good working condition and is powering the car’s electrical system, this is not recommended.
You can easily damage the car alternator or the car computer. Switch off the car engine first before removing the car battery or disconnecting the battery terminals.
How to Change a Car Battery Safely
Do not attempt to change a car battery or even disconnect the battery terminals while the car engine is running!
Swapping a car’s battery with another while the engine is running is dangerous.
Do this instead to remove and connect another battery.
Steps to Disconnect a Car Battery
1. First, switch off the car engine. Disconnect the negative battery terminal (black cable) from the battery post (marked with a – sign)
2. Next, disconnect the positive terminal (red cable) from the battery post (marked with a + sign)
Disconnecting them in this order lowers the likelihood that there’ll be an accidental short circuit!
Steps to Connect a Car Battery
1. With the car engine still off, first, connect the positive terminal (red cable) to the battery post (marked with a + sign).
2. Next, connect the negative terminal (black cable) to the battery post (marked with a + sign).
Start the engine. Some cars may run rough initially.
Or the idle RPMs can be as low as 500 for a few minutes as the car computer relearns the optimum settings for the car. This should stabilize shortly.
Tips to save Memory settings when Changing a Car Battery
If you do not want to lose the memory settings of the car (seat, mirror position, station presets) when the car battery is removed, try this.
1. Connect the Car Battery Terminals to a trickle charger
Connect the battery terminals to a car trickle charger (with the battery still connected).
Next, disconnect the old battery terminals from the battery posts. (The trickle charger will keep the car electronics powered and their memory settings intact).
Lastly, connect the new battery posts to the battery terminals securely (make sure you do not reverse the terminals).
With the battery terminals firmly connected, remove the trickle charger connections.
Hope this little trick saves you time that you’d otherwise spend programming your car radios stations and other settings. Thanks, @Selinger from RA4 World.
2. Use a car battery memory saver
Alternatively, you can also use a memory saver. It has a 12V battery with a cigarette lighter plug that can be plugged into the cigarette lighter socket or charging port to save the memory settings.
You may also be interested in this post: How long the car battery lasts with the radio on?
Related Topics
How to Change a Car Battery without Losing Settings
You can stop the car from losing its saved settings when changing the battery with a memory saver.
It has a 12V battery with a cigarette lighter plug that can be plugged into the cigarette lighter socket or charging port to save the memory settings.
Closing Thoughts
Avoid changing the car battery while the car engine is running. Doing so can damage the alternator and or other electrical components in the car.
If you are planning to do this because you want to avoid using the computer and car radio settings, use a memory saver to preserve the computer and radio settings instead.
