The battery terminal connector is the link between the battery of your car and the electrical system.
If you have a heavily corroded or broken terminal connector or post, you might be wondering if you can replace them.
And, if you can, if it’s a one-size-fits all problem or if different models need different sized terminals.
Battery terminal connectors come in different sizes that correspond to the size and shape of the battery terminal post. Some of them are narrow and tall, while others are shorter and wider. Battery posts with both tapered sides and straight sides are available. The cable connector that you choose must match the battery post, so they are not “universal.”
The first thing we need to do is to clear up some terminology.
Depending on the source, the word “terminal” is used interchangeably to mean the battery cable connector or the battery post itself.
In this article, “terminal” will refer to the battery post and the part that connects the battery cable to the post will be called the “terminal connector.”
Why Kind Of Battery Terminals Are There?
Most American cars use standard SAE lead posts, but not all of them do. Some cars use JIS posts, which are slightly smaller than SAE posts.
JIS posts are found in many Japanese cars.
General Motors and some other auto manufacturers have started using post terminals on the side of the battery.
On these types of batteries, both terminals are the same size, and it is possible to place the incorrect polarity battery post in the hole or switch the connectors. You cannot exchange posts designed for top-post batteries and side-post batteries, or the other way around.
The most common battery post size is 10mm, but some vehicles use 11mm, 12mm, or 13mm terminal posts.
The size of the post can differ according to the manufacturer and model of the vehicle.
Some battery terminal posts use US sizes, with a ½-inch or 9/16-inch being the most common size.
Another thing to consider when replacing battery terminal posts is their composition. Most battery terminal posts are lead, but you can also find them in copper and brass.
Specialty battery terminals are also available that have technology like a built-in digital voltmeter.
Which Battery Post Is Bigger?
On most cars, the positive terminal is slightly larger than the negative one. This is to prevent accidentally swapping the terminals.
If you accidentally put the terminal on the opposite polarity side from the one it was designed for, you run the risk of causing significant damage to your car.
In most cases, the difference in terminal size is significant enough that it would be obvious if you made a mistake and placed the wrong post on the incorrect side.
This is not always the case, which is why you need to be familiar with both your car and the individual battery before attempting to replace the terminal connectors or posts.
Make sure to read all directions to make sure you install them correctly.
Can You Change Car Battery Terminals?
If your car is slow to start when the car is not that cold, it can be a loose or badly corroded battery terminal connector or battery post.
Another sign that your terminals or connectors might be bad is that your lights might dim, or your audio and navigation might slow down.
Another sign that your battery terminals and connectors might not be making proper contact is that your dashboard lights are dim.
When your battery terminals are loose, corroded, or broken, it will not allow a proper electrical contact to be made.
Continuing to operate the car with bad battery terminals can stress the alternator and cause the battery not to charge properly. It can also cause the electrical system to fail.
If you suspect that your battery terminals are the problem, it is important to change them as soon as possible. You change them yourself using the following steps.
1. Safety First
The first thing to keep in mind is that working on a car battery is dangerous and carries the possibility of electrical shock. Make sure to turn off your car and remove the key.
Next, lift the hood and identify the positive and negative terminal. Make sure to wear protective gloves, because battery acid could cause burns to the skin. Also, make sure to wear safety glasses.
2. Remove the Connector
Locate the nut on the side of the terminal connector. Use an adjustable wrench to loosen the connector until it can be easily removed from the post.
Always remove the connector from the negative terminal first to prevent sparking.
3. Replacing the Battery Terminal Connector
Depending on the type of connector, the end that connects to the wire will be different. You need to use wire cutters to snip the wires from the old connectors.
Use a pair of wire strippers to remove just enough of the wire covering to allow the wire to fit inside the new connector end. Do not allow any wire to be left exposed.
Some terminal connectors use a clamp, and you must curve the wire around the screw posts.
For others, you must insert the wire into the sleeve and crimp it. There are other types available, too.
4. Replacing the Battery Post
Some of today’s batteries do not have posts that can be removed. If the posts can be removed, it is a simple process of using a pair of vice grips or channel locks and unscrewing the threads.
The new ones screw into place. Make sure they are hand tight, and then give them an extra quarter turn with your tools.
5. Replace the Terminal Connectors
Next, you can reconnect the battery terminal connectors to the proper posts, starting with the negative terminal first this time and the positive terminal last.
Now, you can put your key in the ignition and make sure everything works.
What Will Happen If You Interchange Battery Terminals?
Most battery terminals are two different diameters, with the positive terminal larger than the negative one. You cannot fit the positive terminal into the hole for the negative one.
You will not be able to tighten the terminal properly if you put the negative one in the hole for the positive terminal.
If you accidentally exchange the battery terminal posts in a car where they are the same size, the best that can happen is that you will not resolve your electrical problems. You might even develop a few more issues because they are not making a proper electrical connection.
This can cause your car to not be able to start, have dim lights, or it can cause critical engine electronic components and sensors not to work.
The worst that can happen is that you can cause a fire or at least cause significant damage to all the electrical components of your car.
This can get expensive and can cause permanent damage in some cases. You can blow fuses, ruin computer modules, and destroy things like starter components. This is why you should avoid accidentally switching the battery terminal posts when you are replacing them.
The same is true when connecting the battery terminal connectors or jumpstarting your car.
Now you know what you need to consider if you need to replace your battery posts. You can do it yourself, but if you make a mistake, you could cause significant damage to your vehicle.
If you are uncertain about anything regarding your battery terminal posts or connectors, it is best to take it to a professional mechanic.