Battery Replacement

Is your car battery dead and you need to replace it? Want to save a considerable amount of money by changing it yourself? We have created this guide and video for you to read and watch so you can do it yourself and get the job done correctly while using everyday tools.

When car batteries go bad they can expel acid around the mounting box and cables which you don't want to get on your clothes or skin so it's a good idea to wear rubber work gloves like you would use to clean your house oven. By sprinkling baking soda over the battery and then rinsing it with water will help clean the area before you begin working.

If you are not sure if the battery is the problem then you will need to do some testing which can be done easily without a load tester. Never touch a metal object between the two terminals.

See Also: Battery testing Here is a list of reasons this unit can fail
  • It has aged more than 3 years
  • Alternator is under or over charging
  • There is an electrical draw (parasitic) on the system
  • It has been dead for an extended amount of time

I will go over these problems is detail further down in the article and how to test the charging system once you have completed the job. But for now sit back and watch our video which gives you an idea on what you are in for when replacing the battery.

Though appearances may vary for each car the process is the same, the only differences is the location which can be in the trunk, under the back seat or hood. Locations under the hood include right rear, right front or left front. If you cannot find the unit refer to the owner’s manual for the exact location. A battery box is bolted to the frame, inner fender well or body and is used to hold the unit in place using a hold down clamp or J bolt with a strap across the top. There might also be a cover over it which shields the unit from outside temperatures which prolongs its life expectancy.

Battery cables are used to connect to the electrical system of the vehicle and the starter. The positive cable connects directly to the starter solenoid while the ground cable is connected to the engine block.

Tools and Supplies Needed

  • Baking Soda
  • Wire Brush or terminal cleaner
  • Replacement Battery
  • Tool Set
  • Protective gloves and eyewear

Step 1

Record the radio stations for re-entry as they will be lost once the electrical power is disconnected. Using a wrench loosen the bolt for the negative cable end, you might need to give a twisting motion to help remove the cable. Be careful not to touch the wrench to the positive side of the battery to avoid short circuits. Always undo the negative side first because the positive side is more prone to shorting to ground via the metal wrench or ratchet being used.

Then push the cable away to avoid it coming back and reconnecting to the terminal.

Step 2

Next, undo the positive side cable this will normally be a red color and identified by a positive sign near the terminal connection. Use a wrench or ratchet to loosen the cable end, at this point there is no chance of creating a short circuit because the circuit is no longer live with the disconnection of the negative cable.

Step 3

Some manufacturers have a cover which now can be removed to gain access to the hold down bolt. This cover should be cleaned before re-installation with water and soap to remove any acid residue that might be present.

Step 4

Locate the hold down bolt or J bolt nuts which are either at the top or bottom of the mounting box, if the hold down is at the bottom it with only require one bolt to be removed while J bolts will require two nuts to be removed. On a bottom bolt style of mount use a long ratchet and extension to help the removal. There will be a wedge style of plastic piece that will need to be removed as well.  Also, wash these parts with soap and water before reinstalling them. 

Step 5

After moving the bolts and hardware and while still using gloves, grasp the battery and wiggle it slightly to break it lose from its mount. Then hold tight as you lift the unit from the vehicle, brace your knees and back for this step due to the weight of the unit. Now is a good time to use a garden hose to wash the area free from acid for a fresh install of the new part. This will also prevent corrosion of metal pieces and wiring which could be routed below the box.

Step 6

Now that the old unit has been removed, compare it to the new battery while checking the size, terminal position, cold cranking and reserve amps which should be the same or similar. Recycle old unit at any an approved recycling center or auto parts store.

Step 7

While holding the new unit firmly, gently lower the new battery into position. Be mindful of the orientation and install it the right direction so the electrical cables will be connected the right way. Never attach the positive cable to the negative side and visa versa. This will cause major electrical problems such as shorting out the alternator, main computer or any other controller in the vehicle. 

Step 8

Once the new unit is in place wiggle it to ensure it's down into the box mount, then lower the mount wedge and bolt into place. This wedge should only be installed in one direction with the stepped part toward the batteries side wall while lower it onto the box bolt hole.

Step 9

After the hold down has been lowered into position, tighten the bolt securely at this point you will see and feel the unit get tight within the box.

Step 10

Next, remove both terminal covers which are used to prevent damaged and shorting while in shipping. They should be clean and ready for the positive and negative cable to be installed. Set the cover back into place before the cable installation.

Step 11

Before re-installing the cables use a cleaner tool with a twisting motion that will create a fresh metal surface within the cable end to aid in the transfer of amperage needed to crank the starter over. Take note this cleaner has a taper fit and will only work correctly in one direction, complete the operation by doing both negative and positive ends. 

Step 12

Then, install the positive cable and tighten while holding the end downward to help the connection. Once the bolt is tight, double check the installation by wiggling the end slightly to ensure a proper fit.

Step 13

Once tight, reinstall the positive cable protective cover. This cover helps prevent accidental short circuits when working in the engine bay.

Step 14

Next, install the negative cable end onto the terminal and tighten wile holding downward. Check the cable end for tightness by giving it a twisting motion. Do not connect the negative end before the positive because the circuit will be live while installing the positive cable which can lead to a system short. Wipe away any dirt or metal shavings from the cable end cleaner and double check your work, you are all set.

Step 15

Once the replacement is complete it's a good idea to check the alternator voltage output using a voltmeter, also observe the electrical system warning light or gauge, this will ensure the operation of the new unit.

Also see: Testing alternator voltage

A new battery can go dead and fail prematurely if there is a parasitic draw which will occur overnight, the system should be tested for this condition to ensure a long life.

Also see: Battery is dead in the morning - draw test


A vehicle battery stores electric energy to start the engine and operate accessories in the electrical system throughout the car when the engine is not running and is equipped with a positive and negative terminal from which a cable is attached. These cables route power from the terminals to the power distribution center or fuse panel and engine block.

Because most assemblies are filled with acid, use caution when working or testing by wearing protective eye wear, gloves and clothing.

Batteries work in two ways, first it supplies the voltage the car needs to operate, next it produces enough amperage to turn the starter motor. If it fails in either of these categories the engine will not crank over. Most repair shops have a amperage tester but you can perform your own amperage draw test using the vehicle as the tester. Learn more

The car battery is a rechargeable cell in the SLI (starting-lighting-ignition) variety which are lead acid based which are the oldest style of rechargeable electrical supplies and is divided into 6 separate cells, each cell produces about 2.1 volts which ads up too 12.6 volts. As the state of charge decreases the voltage and amperage it produces also decreases. Electrical power is created through a chemical reaction where positive and negative lead plates are immersed in an electrolyte solution (acid).

This solution is a combination of water and sulfuric acid. When this solution interacts with the lead plates, the chemical interaction creates voltage. This voltage is then released through the positive terminal (red) and returned to the negative terminal (black).

Voltage from the alternator maintains the batteries state of charge. This continuous cycle can produce electricity for three to four years.

The most common way to recharge this unit is by a process called trickle charging and is performed using an inexpensive charger. Most repair shops have a more powerful and more expensive battery charger that is capable of charging at a higher rate over a shorter time period. To jump start a car, a set of jumper cables is needed.


When the battery is overcharged or jump started, water in the electrolyte solution is transformed into hydrogen and oxygen. This can cause an explosion if a spark or another source of ignition is present. It also decreases the fluid level inside can expose the lead plates. Exposure to oxygen can damage these plates and reduces their ability to provide the chemical reaction needed.

Inspect batteries regularly, if acid is present replace it and check the charging system. Be extremely careful when handling it using gloves and eye protection which are recommended as the acid is highly corrosive. When re-charging use caution, always connect the charge leads while the charger is off, this will prevent a spark from being created. A battery is most prone to an explosion after a recharge.

There are deposits that can form on the positive an negative terminals. These deposits are corrosive by-products of a normal usage form charging and discharging. While wearing protective goggles and clothing, use a garden hose to rinse the battery completely also rinse the surrounding area, this will dilute the acid to a non-corrosive state. You can also apply baking soda to help neutralize the acid. Use a wire brush on the terminals to clean thoroughly and reassemble.


  • Fully charged
  • Store in a cool place
  • Check it every two months and recharge if needed
  • Remove all electrical connectors

Cable Replacement

If excessive corrosion on cables are observed they should be replaced. Corrosion can cause high resistance resulting in a failure of the starter because of overheated the internal winding. Avoid using after market cables as they may not be manufactured to proper specifications resulting in poor performance.


The old assembly is completely recyclable, contact your local recycling station, auto part store or repair garage, do not discard into landfills.

If you need more information please visit our forum where thousands of battery questions have already been answered by our online mechanics.

Article first published