Most car batteries need to be replaced every four to five years. In hot climates, the service life of a wet cell lead-acid battery may only last for two to three years.
It’s usually easy to determine when your battery is nearing the end of its service life. A failing car battery will begin to spin the starter noticeably slower if you’re paying attention. If you begin to notice slower starter operation, get the starting and charging system checked by a professional. A failing starter or a voltage-dropping connection can also cause the starter to spin slowly, and low voltage will eventually destroy a good starter.
To learn how to replace your car battery on your own, check out our guide below.
Car Battery Replacement: How-To
If your battery needs replacing, and you’d prefer to do it yourself, below is a step-by-step guide to help you through the process.
Replacing your car battery can be divided into three major steps: preparing what you need, removing your old battery, and installing a new one.
Note: The following are general guidelines for educational and entertainment purposes only. Consult a repair database or repair manual for specific repair instructions and recommended safety procedures.
Always wear eye protection while working on or around a vehicle battery. A lot of people get away with not wearing eye protection time and time again, but no matter what, protect your eyes. Batteries can explode, and sometimes do. Safety glasses don’t cost much. Eyes are irreplaceable.
First, make sure you have the right replacement battery and that the positive and negative posts are on the same ends of the new battery as they are on the old battery–that’s important. Note the + and – symbols next to each post and be aware that the positive post is slightly larger than the negative post.
Tools Needed to Replace a Car Battery
- Battery terminal grease or anti-corrosion washers (optional)
- Battery post cleaning tool (optional)
- Battery cable terminal cleaning tool (mandatory)
- Wrench (the right size)
- Ratchet, extension, and socket (the right size for the hold-down bolt(s).
- Latex or Nitrile moisture proof gloves (to protect your hands from any corrosive chemicals)
- Safety glasses (mandatory)
- Memory saver (optional)
You’ll need a wrench to loosen and tighten the battery clamp bolts and nuts, as well as a ratchet, extension, and a socket for the battery hold-down. You’ll also need latex or nitrile moisture proof gloves to protect you from leaked battery acid.
Some car manufacturers recommend the use of memory savers to prevent issues after installation, but those only work if you have the right one. The best ones are those that plug into the Data Link Connector port because pin 16 is always B+ and pins 4 and 5 are ground. Your radio presets and other operator preferences may be cleared out once you install a new battery. You may even be required to re-enter a security code to get your stereo working again.
Not all car manufacturers will require a memory saver. It is important to be aware of your car manufacturers specifications before proceeding with replacing your car battery.
Car Battery Replacement Instructions
Now that you’ve got all the materials you need, it’s time to get started on replacing your car battery. Here is a step-by-step guide on how to do this procedure safely:
Car Battery Removal:
- Put on your safety glasses and protective gloves.
- Locate the positive (+) battery terminal and take note of it. This will help you install your new battery correctly.
- Loosen the screws on the cable clamps to disconnect the battery terminals.
- Remove the negative (-) cable before the positive cable.
- After disconnecting the battery terminal cables, you may now unfasten the battery hold-down strap. If your battery uses a base clamp instead of a metal hold-down strap, loosen the bolt holding the clamp against the base of your car battery.
- Lift the battery out of its tray or compartment. Usually, the battery will have a strap on top to make removal easier. If it doesn’t come with one, you may use a battery carrying tool to hold the battery and lift it out. Typically, the battery also has a wedge-shaped indentation at the bottom on all four sides that matches a lip or lips in the battery box.
- Make sure to keep your battery in an upright position to prevent spilling battery acid out of the caps or vents. Of course, if you’re using an absorbent glass mat (AGM) battery, you won’t have this problem as it doesn’t hold liquid.
- Once you’re done removing the car battery, make sure to inspect the battery tray underneath. If it is damaged or corroded, clean or replace as required.
Warning: Battery acid can cause painful burns. If you accidentally touched leaked acid, wash your hands immediately with water and neutralize the acid with baking soda. If you get acid on any cotton clothing, it should never be worn again.
Car Battery Installation:
Now that you’ve successfully removed your old battery, it’s time to install the new one.
1. But wait—before installing your new battery, make sure to test its charge level with a digital voltmeter. If you don’t know how to test a car battery, you may refer to online repair manuals and guides.
Ideally, a fully charged battery will yield a voltage reading of about 12.6 to 12.7 volts.
If you get a lower voltage reading, you’ll need to charge the battery before you can install it. Although car batteries usually come precharged, they may slowly lose their charge, especially if they remain unused or shelved for a prolonged period of time.
Note from Richard McCuistian, ASE Certified Master Automobile Technician: When you start the vehicle after the battery is installed while checking the voltage, you should see from 13.5-14.5 volts if the alternator is working properly, but no more than that.
2. Place your battery on the tray. You may now install the base clamp or strap.
Make sure to safely secure the battery by tightening the clamp or strap, as excessive vibration can damage your car battery.
3. Clean the battery posts with a battery post cleaning tool. Clean the inside surfaces of the clamps attached to your battery cables as well.
A clean surface will help ensure efficient electric contact.
4. Install the positive cable, then the negative cable.
5. Tighten the clamps—but be careful not to over-tighten as you may end up damaging them.
6. To prevent corrosion, apply a thin coating of battery terminal grease on the clamps and posts. You may opt to install anti-corrosion washers on each post as well to help prevent corrosion before installing your battery cables.
7. Make sure to double-check all connections, straps, and clamps. Your car battery should be safely installed at this point.
You may start your vehicle to make sure that everything is working as it should.
If your vehicle doesn’t start or crank, try cleaning and tightening the battery cables. Check for other loose cables including the one connected to the chassis ground and the power center.
Then, try starting your vehicle again. If it still won’t start, chances are your vehicle may have another underlying issue, such as a starter circuit problem. Have your vehicle inspected by a professional mechanic to get a proper diagnosis.
Helpful Tips on How to Replace a Car Battery
If you’re a visual learner, here’s a helpful video that should give you an idea of how the car battery replacement process should go:
A Closer Look at the Car Battery
A car battery is more or less like an electric gas tank. It begins with a certain number of cold cranking amps, but with every passing year, that battery’s actual CCA decreases until the battery can no longer supply the energy to spin the starter.
All batteries operate the same way: they lose their ability to store energy over time, and your battery will never choose a good time to fail. Sometimes batteries can fail suddenly and without warning. A battery is basically a collection of 2 volt cells, and there are multiple connections within a battery, any of which can fail by shorting out or becoming open circuits.
Premature Battery Failure
There are several factors that can cause premature battery failure. For just one example, a battery that has been completely drained repeatedly due to a parasitic drain will lose its CCA capacity very rapidly, unless it happens to be a “deep cycle” battery such as used in marine applications.
Not driving your vehicle long enough to fully charge your battery may cause it to remain chronically undercharged shortening its natural service life. However, that would be something like driving it 100 yards up the street and back every day, so short drives aren’t usually a factor in battery life as much as they are in building engine sludge due to an engine that routinely doesn’t get to operating temperature.
One thing that will discharge even a good battery on some vehicles is to spend too much time idling or driving very slow while using high-current accessories. The alternator needs to spin above idle speed for optimum output, but on most modern cars the alternator can keep up with accessory load.
The alternator on a vehicle does an amazing job of charging the battery even on short drives. Extreme engine compartment heat will cause battery damage as well by boiling the electrolyte out; that’s why so many batteries are surrounded by plastic boxes when the car is new. Some have bubble wrap around the sides of the battery for that same reason.
Mishandling and severe vibration due to an improperly mounted battery can ultimately loosen or short out internal cell plates if the vehicle is driven over rough terrain, which can cause sudden battery failure. Sometimes (not often) a battery can literally explode under the hood while you’re trying to start the vehicle. To avoid these potentially costly and harmful scenarios, make sure your battery is always in good condition.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.