How to change your Car battery SAFELY (Which wire to disconnect first) – Plus don’t lose your car memory settings

Blog_Cars_How to change Car battery SAFELY - Which wire to disconnect first. Plus don't lose memory settings

Need to know how to change a car battery safely, the right way?  In this post I’ll go over how you can replace your car battery safely and not get hurt.  Installing a new battery in your vehicle is an easy maintenance DIY that doesn’t take too much time or need many tools.

Read this step-by-step guide or watch our video here and we’ll guide you all the way.

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The video also has an electrical short circuit demo to understand which wire terminal to remove first (Positive or Negative) because removing the wrong cable first will make it more dangerous and could result in an electrical shock, the battery exploding, a fire or you getting seriously hurt.

Before you get started…

If you’re not sure where the battery is located, check the owners manual.  Some cars have the battery located in the trunk and not in the front under the hood.

Vehicle owner's manual for car and maintenance care info
Vehicle owner's manual

You should consider using an OBD vehicle memory saver to keep all your vehicle settings saved.  Some cars have issues when the memory is lost due to power outage/battery change.  Also, use one if you are worried about keeping your radio station pre-sets and other vehicle settings that may be lost when you unplug the old battery.  Some vehicles also have a stereo system that needs a security code to be entered if the power is lost.  This is to prevent stolen stereo systems from being used without the code.


Vehicle OBD Memory Saver

In some cases, some vehicles may idle rough for the first few trips until it relearns the air fuel ratios.

Note too that some newer or luxury vehicles have so many sub-systems that when reset (due to battery change) will need to be re-initialized by expensive equipment at the dealership.  Investing in one of these OBD memory saver devices can save you a lot of time and headaches.

Disclosure:  Some of the links in this post are affiliate links.  As associates of Amazon, Ebay and others we may earn a small #CommissionsEarned, at no cost to you, if you click through to make a qualifying purchase.  This helps support our work and allows us to continue to provide great content to our viewers and followers.  We link to products we use, are similar or better based on their quality and usefulness.  We are not sponsored by anyone to endorse these products.  The decision to purchase is yours and using any of our links does not affect the price you pay.

Check the end of this post for a link to the products.

Safety check

Before you start, ALWAYS wear safety glasses and gloves for protection.

Check out the Bonus Tip at the end of the post.

Step 1

Positive or Negative (Red+ or Black-)?  Which wire do you remove first?  This is very important to ensure safety and prevent chances of you getting hurt.

You will need to determine if your car is negatively grounded or positively grounded.  Most cars are negatively grounded and so the negative wire is removed first.  Remove the positive wire first for positively grounded cars.

And here’s why…

When the car is negatively grounded, it means that the negative terminal of the battery is basically connected directly to the body and metal components of the car.  The car effectively becomes the negative terminal of the battery.  If you were to make a connection from the positive terminal of the battery to any metal part of the car you would create a short circuit which would create a big spark that could lead to a fire, the battery exploding and you getting hurt.

This could easily happen during removal of the positive wire without first removing the negative wire.  When using a metal wrench to unbolt the positive wire, it is in contact with the positive terminal of the battery and if you then accidentally touch any metal part of the wrench to any metal part in the engine bay, you would cause a short.

So check your car’s owner’s manual if you are not sure.  There will be a battery section!

For removing the terminal cables, typically, a 10 mm socket is usually the correct size to use.  Check your manual to be sure or just try out on your cable to get the correct size.

Once the correct cable is removed first (Usually, Negative-), the car body and any attached metal part is no longer connected to the battery and so no short circuits can happen.  Of course, you still need to make sure that you don’t accidentally touch the 2 poles of the battery with anything conductive, like a wrench.

Step 2

Remove the other cable (Positive+ cable in our case).  Make sure both cables are out of the way and have no way to accidentally flipping around and touching the terminals of the battery.

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Step 3

Remove the bracket holding the battery down.  On a battery bracket like this one, you will have to make sure to hold on to the bars so that they do not drop into the engine bay.  You could also leave them attached by just loosening enough until you can remove.  This may make it easier to install on the new battery.

Step 4

Remove the battery.  Be careful as you want to keep the battery upright and vertical and don’t tilt the battery accidentally while transporting it.  It is quite heavy so make sure to have proper footing and lift using your core muscles to avoid injuring yourself.

Step 5

Clean and dry the plastic battery cover and battery tray if you want and reinstall.

If you need to charge your car battery instead… find out 

What to use and How here!

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Click here to load the video to view the description

Step 6

Carefully install the new battery in the same orientation as the old battery (Polarity must be similar).  Make sure to keep the battery upright to prevent acid leaking out.

Step 7

Reinstall the battery bracket, making sure that the hook is installed correctly.  Loosely attach both ends and adjust as needed before final tightening.  Then tighten down and make sure the battery is solidly held in place without over tightening.  The battery should not be movable.

Step 8

Remove the protective plastic caps then clean both battery posts and cable terminals with a battery post terminal cleaner brush.  Clean the shavings off.  Make sure not to breathe in the particles scrapped off or let it get into your eyes.  There are metal shavings and corrosive particle in it.

Step 9

Apply di-electric grease to prevent corrosion.  This can be applied at the end too, after both connectors have been attached.

Step 10

Install the cables in the reverse order of removal.  In our case, Positive then Negative (In our case).  Don’t over tighten.  The cables should not be movable.

Step 11

Remove all tools, shop towels and objects from the engine bay that doesn’t belong there.

Remove your memory saver if one is used, then try to start your car.  Everything should work.

Bonus Tip below…

Purchase Tools

Bonus Tip

When you by a new battery you may be charged an environment fee.  This is to ensure that you bring back the old battery for recycling instead of throwing it out.  You can get the fee back by returning the old battery to the place where you purchased the new one.  Just make sure you kept your receipt and bring it with you.

Sometimes, you will encounter someone that doesn’t know about the environment fee and doesn’t want to refund that to you.  That’s what happened to us.  I just asked to speak with someone higher up like a manager and they will usually know what to do.

We hope you found this post useful.

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