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How to Replace Battery Terminals

Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.

Corrosion not only prevents proper electrical flow but will destroy your battery terminals.

Corrosion not only prevents proper electrical flow but will destroy your battery terminals.

You want to replace battery terminals whenever they oxidize, crack, wear out, or when you can't tighten them up any more. A car battery requires a tight and clean connection between each post and the cable it attaches to.

Potential symptoms of bad battery terminals include:

  • dim headlights and poor operation of other electrical systems
  • overheating of battery post and terminal
  • overheating of the starter motor
  • starter motor short service life
  • hard to start engine
  • poor charging of the battery
  • failed alternator
  • damage to electrical components
  • dead battery

In most vehicle models you can replace battery terminals in about an hour or less, using a few common tools.

Restoring a good battery connection will help restore proper operation of all electrical systems in your vehicle, and help extend your starter motor service life and other components.

This simple guide will help you replace one or both terminals at home.

Index

Tools and Materials

I. Saving Car Computer's and Accessories' Settings

II. Disconnect the Battery Terminals

III. Clean the Battery Cable Ends

IV. What Type of Battery Terminals Should You Use

V. Replace the Battery Terminals

VI. Connect the Cables to the Battery

VII. Protect Battery Terminals and Posts from Corrosion

Test Your Knowledge of Battery Clamps

Preserving Memory Settings

The computer in your car uses information from several systems' sensors to optimize engine operation...use a computer memory saver...to preserve memory settings....

Tools and Materials

Some useful tools you may need for this repair project

Wrench or socket set

Pliers

Diagonal cutting pliers or utility knife

Battery post wire brush

Baking soda and warm water, if necessary

New battery terminals

Heat shrink tubing, if necessary

Felt washers

Petroleum jelly

Use a computer memory saver to preserve your vehicle devices' settings.

Use a computer memory saver to preserve your vehicle devices' settings.

I. Saving Car Computer's and Accessories' Settings

The computer in your car uses information from several systems' sensors to optimize engine operation based on your driving patterns and other factors.

Disconnecting the battery will make your computer lose these settings. And it can take a few hundred miles of driving for the computer memory to relearn this strategy.

When you disconnect the battery, you also lose security and radio settings. On some models, rough idle and other driveability problems show up, or you simply can't start the engine.

To avoid this, you can use a computer memory saver. A memory saver is an inexpensive device that uses a 9V battery. The memory saver connects to the cigarette lighter or an auxiliary power outlet to preserve memory settings for the different devices in your vehicle like the computer, radio and alarm. It can save you from a lot of trouble.

Make sure to turn off all accessories, and keep them off while working on your battery.

Carefully disconnect the battery terminals.

Carefully disconnect the battery terminals.

II. Disconnect the Battery Terminals

To avoid the possibility of a short circuit while disconnecting your battery, always detach the negative cable first and then the positive cable.

  1. Loosen the terminal bolt holding the negative (black) battery cable to the post using a wrench. Then detach the terminal and cable from the battery post.
  2. Loosen the bolt and disconnect the terminal holding the positive (red) battery cable to the battery post.
  3. You may need to use a screwdriver to pry open the terminal in order to detach it from the battery post. If you still have difficulty detaching the terminal, use a battery terminal puller.
  4. Cut off the damaged terminal with a pair of wire cutter pliers or use a hacksaw. Cut at the wire as close to the terminal as possible. If the battery cable is still attached to the vehicle, you may want to use a small piece of wood or something similar as surface support while cutting the terminal off the cable.
  5. After cutting off the terminal, if the end of the cable is badly corroded or show signs of damage, trim back the cable, but make sure the cable will reach the battery; otherwise, you'll need to replace the cable as well.
  6. Strip back about 1/2-inch of insulation from the end of the cable using a pair of diagonal cutting pliers or a utility knife.
Battery clamps should be clean and tight.

Battery clamps should be clean and tight.

III. Clean the Battery Cable Ends

Whether the cable ends are free of corrosion or not, it's a good idea to clean them and get them ready for the new terminal you want to install. This will ensure a good contact and electrical flow.

Also, you may need to remove corrosion from the end of the battery cable or from one of the battery terminals. Cleaning a cable end or removing corrosion is a simple process:

  1. Clean up the wire strands on the cable end with a wire brush to restore their original shine.
  2. If there's some corrosion, soak the end of the cable for a minute or so in a solution of baking soda and warm water; and then brush off the corrosion using a wire brush.
  3. However, if there's too much corrosion along the cable strands, you may need to cut the cable back. But don't cut the cable too short that it won't reach the battery post; otherwise, replace that cable -- or cable set.
  4. Use the same solution of warm water and baking soda to remove corrosion from a terminal and battery posts. Use a soft brush to apply the solution and, if necessary, a wire brush to scrub the terminal free of corrosion.

The following video will give you a visual reference for cleaning and protecting your battery terminals as well.

IV. What Type of Battery Terminals You Should Use

You can find replacement battery-cable terminals at most auto parts stores.

The most common, and cheap, are the bolt-on battery terminals. However, this type of terminal not always provide a good connection and is more prone to corrosion buildup.

If possible, choose the battery compression terminal type, which makes a complete contact all around the end of the cable, ensuring good current flow.

Some auto parts may sell OEM molded-type battery terminals, also a good choice, but you'll need a crimping tool for the installation.

Bolt-on type battery terminals are not as efficient as compression type terminals.

Bolt-on type battery terminals are not as efficient as compression type terminals.

V. Replace the Battery terminals

When making the installation, make sure to place the correct terminal for each battery cable. Usually, the positive battery cable uses a larger terminal to accommodate the larger positive battery post.

A) To install a bolt-on battery terminal type:

  1. Loosen the bolts on the new terminal, so the terminal opening is wide enough for the battery cable end to enter.
  2. Slide the stripped end of the battery cable into the terminal--and any additional wire grounds, if you are replacing the negative battery terminal.
  3. Tighten the terminal bolts using a six-point wrench or socket.
  4. Repeat the procedure to replace the other terminal, if necessary.

B) To install compression-type terminals:

  1. Slide a piece of heat shrink tubing over the battery cable. Use red for the positive connection and black for the negative connection.
  2. Push the end of the battery cable into the compression nut.
  3. Hold the compression nut with a wrench.
  4. Start threading the terminal on the compression nut and tighten the terminal using a wrench.
  5. Slide the piece of shrinking tubing back over the compression nut and terminal base.
  6. Shrink the tubing using a heat gun, hair dryer or lighter to protect the connection against corrosion.

C) To install OEM molded-type battery terminals:

  1. Slide a piece of heat shrink tubing over the battery cable.
  2. Position the stripped end of the battery cable inside the terminal cavity.
  3. Use a crimping tool to lock the cable and terminal together.
  4. Slide the heat shrink tubing over the terminal base and cable.
  5. Use a heat gun, hair dryer or lighter to shrink the tubing. This will protect the connection against rust and corrosion.
Check each battery cable for corrosion and damage.

Check each battery cable for corrosion and damage.

VI. Connect the Cables to the Battery

  1. Clean the battery post(s) using a battery post cleaning tool, if necessary.
  2. Before connecting the terminals to the battery, place a felt washer over each battery post and then, starting with the positive side, place the positive battery terminal over the battery post.
  3. Tighten the terminal bolt to secure the cable to the battery.
  4. Repeat steps 1 through 3 to install the negative battery terminal.
  5. Disconnect the memory saver, if you have one connected.
  6. After securing the terminals to the battery posts, apply a thin layer of petroleum jelly around the terminals and posts. Together, the felt washers and petroleum jelly will help prevent corrosion from creeping over the posts and terminals.
Apply a layer of petroleum jelly to the battery terminals for protection.

Apply a layer of petroleum jelly to the battery terminals for protection.

VII. Protect Battery Terminals and Posts from Corrosion

When you replace damaged battery terminals, you are providing a good and clean path for full battery power to feed your vehicle starting system during engine start up, and the rest of the electrical systems during vehicle operation. You also allow the alternator to properly charge the battery.

Corrosion attacks battery terminals whenever acid or hydrogen gas leaks through the base of a battery post. By installing a felt washer on each post and applying a layer of petroleum jelly around the post and terminals, you'll help prevent corrosion from building up.

However, if corrosion seems to turn into a serious problem, most likely you'll need to replace the battery.

Maintaining your new battery terminals and cables free of corrosion is not difficult. Examine the battery terminals and around the battery case twice a year, and clean up the terminals as necessary. This procedure only takes a few minutes and ensures that your car will have all the power necessary to operate properly.

Test Your Knowledge of Battery Clamps

For each question, choose the best answer. The answer key is below.

  1. A loose, corroded or damaged negative battery clamp may:
    • Damage the starter motor
    • Damage the radiator
    • Damage the engine block
    • All of the above
    • None of the above

Answer Key

  1. All of the above

© 2016 Dan Ferrell