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How To Change A Car Battery: What You Need To Know

Car Battery
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How To Change A Car Battery: What You Need To Know

Eventually, every battery wears out. This can be painfully obvious with cars when things like this seem to happen at the worst time. While you shouldn’t assume that a vehicle’s starting problems are always due to a bad battery, understanding what’s involved in replacing a battery is an essential part of car ownership.

But, before you swap out batteries, you’ll want to make sure there are no problems with the electrical system, like a bad alternator. A qualified mechanic can usually identify the source of these problems.

That said, let’s dive into car battery replacement.

Why Do I Need To Replace My Car Battery?

There are many things used in your car that regularly need replacement. Engine oil, radiator fluid, and wiper blades are just a few examples. And of course tires and the battery, too. The mere operation of your car puts stress on these items. And every time you start the vehicle, turn on the audio system or air conditioning or use the headlights, you’re taxing a battery’s capabilities. It’s not much different than the battery in your smartphone. The more you use it, the more you have to charge it.

But eventually, a car’s internal charging system (the alternator) can no longer restore a battery that’s past its prime. Let’s explore the usual causes of a car battery’s deterioration.


Unfortunately, no one has yet to invent the permanent car battery. Over time, the internal chemical reaction (lead and acid, for example) that enables energy storage is no longer effective. A declining battery that was once able to hold a smaller amount of energy suddenly cannot store anything at all. Keep in mind that the typical battery will last from three to five years. But some cheap replacement batteries may be guaranteed for only six or twelve months. More expensive options may offer longer warranty periods.


In addition to age, extreme temperatures are also a car battery’s worst enemy. High summer temperatures and heat from the engine can cause a battery’s internal components to degrade. Additionally, the summer heat can stress the car’s alternator, impacting how well the battery is charged. Irregular charging can also speed up a battery’s death.

But, it’s not only summer that can affect a battery. The simple fact that below-freezing temperatures reduce battery capacity by up to 20 percent already puts things at a disadvantage. Toss in a failing battery to begin with, and the problems can kick in. Plus, cold temperatures also mean that an engine works harder to start (thanks to thickened motor oil). Add in the electrical drain of a heater, defroster, and other accessories. You can probably see where this is heading.

Lack Of Use

Constant regular use actually helps a battery’s condition. Think of it as exercise. When done correctly on a continuing basis, you build up strength. So, a car that only gets used for the occasional short trip will likely not have a well-conditioned battery.

How Frequently Should A Car Battery Be Replaced?

The short answer is when you need to. Yes, you can set an arbitrary period, every three years, for example. But this approach just involves spending more money than you have to. Instead, have the battery tested periodically. It’s simple to integrate this step into your regular maintenance schedule. A mechanic can do this in a few minutes or buy a multimeter (that can handle a car battery) and learn how to do it yourself.

How to Change a Car Battery?

Changing a battery involves a few tools and some simple precautions. The truth is that many auto supply stores will do this for you for free or at a nominal charge, but you have to get to the shop. Something impossible if you can’t start the car.

Here’s what you’ll need:

  • New car battery
  • Safety goggles
  • Work gloves
  • A wrench sized for the battery terminals
  • Shop towel
  • Wire brush
  • Anti-corrosive/cleaner solution
  • Memory saver: a battery-powered device that preserves your vehicle’s seat memory and radio settings. This connects via the cigarette lighter or onboard diagnostic port. A memory saver isn’t necessary if you don’t care about having to reset things. Follow the device’s instructions on how best to use it.

AN IMPORTANT NOTE: If you feel uncomfortable about performing any battery-changing task (including lifting a battery that can weigh 40 pounds or more) or are in an unsafe area (like along a busy road), skip the DIY route and seek professional assistance.

Getting The Car Ready

Ensure the car’s transmission is in “P” (park) and activate the parking brake. Then turn the car off and remove the key. The vehicle should be on a flat, level surface. Otherwise, use a wedge (like a woodblock) against the tire to prevent any rolling.

If the car is parked in a garage, open the door for proper ventilation (battery gases can be explosive).

Open the hood and allow enough time for the engine to cool off. This step ensures you won’t come into contact with any hot engine components.

Find The Battery

While most car batteries are located under the hood, it’s not uncommon to find them in the trunk or under a back seat. Check the owner’s manual if you’re unsure about the battery’s location.

After putting on the safety goggles and gloves, remove the battery cover (if your car has one).

Locate the two battery terminals: Positive (+) usually has a red marking or red cable. The second terminal, negative (-), will typically have a black marking or cable.

Disconnect the Cables

With the wrench, loosen the battery connector bolt for the negative (black) terminal and detach its cable.

Do the same thing for the positive (red) terminal. Both cables should now be detached from the battery.

IMPORTANT SAFETY NOTE: NEVER permit any metal object, like a wrench, to touch both battery terminals at the same time. This dangerous situation may create sparks that can cause an explosion.

Take Out The Battery

Loosen any components that secure the battery to the battery tray. Place these parts aside but keep them secure as you’ll need them for the new battery. You may find it handy to take a reference photo before disassembling anything.

Using caution (remember a car battery is heavy), lift the battery and place it away from the car. If you see any cracks or case separations, put the battery in a well-ventilated area (battery gas may be leaking)

Clean the Connectors

Cautiously use the cleaning fluid on the battery connectors (the doughnut-shaped part at the end of each cable). Let the solution sit for a few minutes.

Use the wire brush to clean the inside of each connector (and the outside, too, if needed). Carefully brush away any corrosion.

With the towel, wipe each connector (inside and out) clean.

Install The New Battery

Take off the protective red and black caps from the replacement battery.

Add an anti-corrosion washer to each battery post.

Apply a small amount of anti-corrosion solution to each battery post.

Carefully put the new battery onto the car’s battery tray, being sure to place the negative and positive terminals in the same position as with the old battery.

Gather the mounting hardware and secure the battery to the battery tray.

Again, MAKE SURE not to allow any metal items to touch the two terminals at the same time.

Reconnect The Battery

Connect the positive (+)/red cable to the positive (+)/red battery post and tighten the connector bolt.

Follow the same steps for the negative(-)/black post.

Make sure the battery is tightly secured to the battery tray and that the cable connectors are secure, too.

Replace any battery post covers or protective panels that you might have removed.

Close the hood or trunk and start the car.

How Much Is A Car Battery?

Expect to pay $125 to $300 for a new car battery. The greater the starting power and promised longevity, the higher the price. Keep in mind that a larger, more powerful engine or car with a sophisticated electrical system may require a more robust battery (which will have a higher price tag). For instance, a compact four-cylinder hatchback won’t need as capable a battery as a large SUV with a powerful eight-cylinder engine.

It’s important to remember that most retailers charge a core deposit (usually about $20) that is refunded when the old battery is returned.

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No matter if you’re coming from Columbia, Towson, Baltimore, or beyond, Trust Auto provides a can’t miss used car dealership experience. Call or visit us today.