Today’s the day you learn to install a car battery

A step-by-step guide to removing the old one and installing the new one.
Car battery.
Let's break it down step by step. Deposit Photos

This article was originally featured on Car Bibles.

Time Needed: Less than 30 minutes, Difficulty: Beginner, Cost: Price of a new battery ($60-300)

Years ago when I still lived in a campus apartment at Ohio State University, I passed by two college kids cluelessly tinkering underneath the hood of a Hyundai Elantra. I had deduced that the car wouldn’t start, and somehow the two had skipped the jumper cables and instead gone straight to replacing the battery. After screwing around with all the controls, they figured out how to pop the hood, looked at the engine, and said, “oh crap, it’s a hybrid.”

There was no Elantra hybrid back then. The two college kids got confused by the cover with a red wire and black wire sticking out of it, shielding a standard 12-volt battery. When they finally got the cover off, they didn’t know what to do next. I don’t want that situation to ever happen again to anyone else, so we’ve gathered a helpful guide all about  how to remove and install a car battery. Let’s get started.

The safety brief

Car batteries are a pretty ubiquitous technology, and the risk of electric shock is generally low. But low risk doesn’t mean no risk. Car batteries should be handled with the utmost care. Before you do anything, consider these tips:

  • Wear long sleeves and long pants, if possible. Your car battery contains a mild acid that stores energy. It can cause acute to mild chemical burns if it contacts the skin. Keep the battery upright when lifting and try to keep it away from your skin. Be sure to inspect your battery, both new and old, for any cracks, bulging, or leaking electrolyte. These are all signs the battery should be immediately replaced.
  • Wear rubber gloves. Even a thin rubber glove will act as an insulator, both from any accidental acid spills, or any stray arcing of electricity. The risks are low, but remember, low risk does not equal no risk. 
  • Wear safety glasses. There are all sorts of fluids, dirt, and grime that build up in an engine bay, where your battery lives. Not only will glasses protect against any potential acid spills, it also keeps irritating particles out. Always wear glasses when working under the hood.
  • Lift with your legs when moving a car battery. Some car batteries can weigh up to 40 lbs. Don’t hurt yourself, lift with your legs, not your back. We’d hate for you to end up with permanent back damage over what should be a simple 10-minute repair.

The tools and parts you need

Generally speaking, car batteries aren’t super complicated to remove and install. A few manufacturers might put them in odd inaccessible places that require extra tools, but that’s unlikely. Here’s what you should need:

  • socket set and/or wrench set. Commonly, the bolts that hold the terminals to the battery in most cars will be held on with 10mm nuts or bolts. If you’re not sure of the size, an adjustable crescent wrench may work, but be careful not to round out those nuts.

The prep: How to remove the old battery

If you’re installing a new battery, that likely means there’s an old battery to remove. Don’t worry, it’s a simple job.

  1. Assure the car is secured and in a safe location. If it’s in a garage, make sure the door is open. Make sure the car is in park (or first gear, if it’s a manual transmission vehicle), with the rear wheels chocked, or the parking brake engaged.
  2. Open the hood or trunk, depending on the vehicle. Occasionally, the battery may be located in a less convenient place. If the location isn’t obvious, check the vehicle’s owner’s manual for the battery location.
  3. Find the negative and positive battery terminals. Remember, positive is red, negative is black. Typically, the positive terminal has a small plastic cover with a plus sign that can be easily pried back. The negative terminal may have a negative sign nearby, but not always. 
  4. Start by removing the negative battery terminal first. Take your wrench or ratchet and slowly crank or turn counter-clockwise. You likely don’t need to remove the nut or bolt entirely off, but just loosen it enough to get the terminals off. Wiggle the negative battery terminal off of the battery pos, and move it out of the way where it doesn’t touch anything. Make sure the battery terminal isn’t stretching or binding too much. 
  5. Repeat the steps for the positive battery terminal and take note of how the terminals are positioned. 
  6. Not every vehicle has this, but remove the battery bracket/brace if so equipped.
  7. Generally, most batteries have some sort of grab handle, but it may be broken or missing entirely. Be sure to take care when lifting the battery out of the vehicle. 
  8. As an optional step, this is a great  time to consider cleaning your battery terminals

The task: How to install a car battery step by step

Once the battery is out and the terminals are cleaned up, it’s time to install the fresh battery.

  1. Take your new matching battery and reinstall it in its home. Be sure to pay attention to what terminals go where and make sure the battery is securely in position. 
  2. If so equipped, reinstall the battery’s securing posts. 
  3. Reconnect and tighten the cable to the positive terminal first, then the negative terminal. The cables should be snug on the terminals, unable to move.
  4. Once it’s buttoned up, make sure everything is working by starting the vehicle. If all’s good, it should fire right up.
  5. Close the hood, make sure all of your tools are out of the engine bay, and you’re done!

FAQs about installing car batteries

We want to try to answer any questions you have. We’ve selected common points of confusion from our experience, as well as commonly asked questions from popular search results. We answered those questions below.

Q: Does it matter which way you install your battery?

A: Absolutely yes. Your battery (and car) is designed to take the battery’s energy in one direction. Positive to positive, negative to negative. Any reversal of this could cause serious damage to the vehicle’s electrical system or battery. Before you remove the old battery, take a photo for easy reference.

Q: How do I know what kind of battery my car takes?

A: That’s trickier, but the battery size and type are generally found in the vehicle’s owner’s manual. If not, the old battery will often have a sticker on the front or top that shows the battery’s size and type. If all of those tricks fail, the clerk at your local auto parts store should be able to ascertain the correct battery type. 

Q: What do I do with the old battery?

A: Most local municipalities, junkyards, and auto parts stores have battery recycling programs. Whatever you do, please dispose of it safely! The materials in car batteries can be very harmful to the environment if not disposed of properly. That “let’s throw our batteries in the ocean” joke is just a stupid meme. Please don’t do that.

Q: Uh, my clock shows 12:00 and my radio presets are gone. What happened?

A: This is normal. Depending on how long the battery was removed, the car’s computerized systems were completely de-energized, which means the car forgot all of its stored settings.

Learn more about car batteries from this helpful video

When written out, the steps probably look longer and more complicated than they really are. Here’s a simple, easy-to-follow video from parts store O’Reilly.