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After a few jumps it's become apparent that you need a new battery. The problem is that the label has rotted off and you can't read any of information on it. You're not sure about the difference between battery sizes and have no idea what to buy. Don't worry, batteries require a little bit of know-how, but everyone can understand what their car needs. It's easy to find the right size and learn what other features you should check before purchase. Here are the answers to your battery-buying questions: 

What Is a Car Battery Size?

The automobile battery size refers to the physical dimensions of the battery. While this seems straightforward, it’s important to remember that the size doesn’t necessarily mean anything more than the height, length, and width. A larger battery, for instance, isn’t automatically more powerful than a smaller battery. Much the same way a small leather hiking boot could be stronger than a large sandal, there are other factors involved.

The group sizes are standardized by the Battery Council International, who provide each battery’s dimensions in both inches and millimeters. The group numbers are generally two digits and may be followed by a letter. 24F, for instance, is a common battery size that fits many Honda, Toyota, Nissan, and Acura vehicles. 

If you have an old battery for your automobile, it should have the group size listed on it. You can also look it up by checking your service manual or searching for the information on the internet. Once you have the BCI group size, you can move on to the other details. 

What Other Information Do You Need To Know About Your Battery?

In addition to the size, your car uses a battery with a specific terminal type, terminal configuration, mounting system, polarity, number of cranking amps, and number of cold cranking amps. You could easily own two sedans that use radically different batteries, even if the style of the vehicles is relatively the same.

It’s essential to have this information when searching for the right product because BCI codes are used on many batteries. Utility vehicles, trucks, golf carts, and go karts also use batteries similar to cars. A unit with the same group size as your car’s might fit in the right spot but it won’t be able to start your engine unless it has the right specifications.  

Cold cranking amps, in particular, are critical to your battery’s operation. Cold weather puts more stress on both your vehicle and your battery. A minimum amperage is required for your car to start and your battery’s CCA has to meet or exceed this number. 

While this can be a little overwhelming, keep in mind that some of this is included in the BCI code. You should also be able to find the relevant information on an old battery, the service manual, or an informative website.  

Measuring Battery Power

Three traditional measures of battery power are listed right on the label.

Cranking Amps (CA) – Indicates the number of amps a new, fully charged battery can deliver continuously at 32° F for 30 seconds while maintaining a voltage of at least 7.2 volts.

Cold Cranking Amps (CCA) – Refers to how much power the battery can generate while “cold,” specifically when starting the engine. This measures the battery’s ability to go from not in use at all to providing a lot of power quickly. Modern vehicles start very quickly so cold cranking amps are not as important on later-model vehicles.

Reserve Capacity (RC) – Shows the number of minutes at 80° F a battery can be discharged at 25 amps and maintain at least 10.5 volts for a 12 volt battery.

How Long Does a Battery Last?

This can be a complicated question to answer because so much of it depends on your vehicle and your driving. While your alternator keeps your battery charged, it can’t hold a charge forever. Batteries have an amp hour rating that provides an approximate number for their longevity. It’s not always written on the label and may not even be in the product description, making it hard to know exactly.

Having said that the size of a battery doesn’t necessarily translate directly to its AH rating. Having said that, larger batteries generally last longer while smaller batteries have less staying power. If shopping online, contact the website directly to get manufacturer information on AH values. 

Regardless of the AH rating, there are some things you can do to increase the life of your battery. Ensure your battery is properly mounted and installed tightly to prevent internal damage. Safely cleaning your terminals from time to time can minimize the spread of corrosion. Practicing good repair and maintenance habits also helps your car run well, which puts less stress on the battery. 

How Does Weather Affect Batteries?

  • Heat is the number one cause of battery failure, and extreme heat can evaporate the water inside the battery. This can lead to corrosion of the internal components and battery failure
  • Cold temperatures dramatically reduce the effectiveness of a battery. Electrons flow more slowly, reducing the amount of energy that the battery provides. This results in a reduction of cranking power and sluggish starting. Batteries left in a discharged state are all susceptible to freezing, which damages internal components

What Are the Different Types of Batteries?

  • Lead-acid batteries are the most common kind. They consist of an outer casing that’s filled with battery acid. The terminals correspond to positively and negatively charged lead plates in the acid. They may not perform as well as more advanced batteries, but lead-acid models are more than adequate for most purposes. They also tend to cost the least.
  • Enhanced flooded batteries (EFB) are built in a similar style to lead-acids but give up to double the cyclical stability. Their construction makes them tougher for better resistance to discharging and vibration. They’re more expensive but also tend to last longer. If your vehicle has stop-start technology, it may have come with an EFB.
  • Absorbent glass mat (AGM) batteries are the most expensive models with the best power. This style became popular in the 1980s after proving its reliability on military vehicles. The name comes from a fine fiberglass mat that is soaked with acid. This makes the battery spill proof, which is excellent for off-road applications. Perfect for high-powered features, you find AGM batteries on sports cars and luxury automobiles.

Does AutoZone Take Old Batteries?

If you need to get rid of an old battery, take it to AutoZone. We recycle used batteries, and if you’re purchasing a new battery, we will give you a core credit to offset some of the new batteries price. Our stores recycle more than just batteries too: you can recycle your old parts and fluids at your local AutoZone.

If you’re having trouble with your battery or your battery is more than four years old, don’t buy a new one before you figure out the issue. Bring the battery by for a test, if it tests low, AutoZone stores can charge your battery for free.

While it’s tempting to buy a high-tech model, you should check your power needs first. Most cars only have basic power requirements that can be fulfilled by a lead-acid battery. Unless you do a lot of off-road driving or have complex systems on-board, you may not need an EFB or AGM battery. On the other hand, if you just had a custom sound system installed, you might need an AGM unit to create enough electricity. 

Now that you know how to choose a car battery size for your vehicle, you can save money by purchasing and installing it yourself. Swapping out a battery is one of the simplest things you can do on your car. Keep it cheap and convenient by ordering your new unit online. Find a reliable lead-acid model or get an advanced AGM battery for your high-performance machine. You can get it delivered right to your door, so you don’t even have to go to the local auto shop.  

Advice, how-to guides, and car care information featured on AutoZone.com and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

FREE Loan-A-Tool® program requires returnable deposit. Please note that the tool that you receive after placing an online order may be in a used but operable condition due to the nature of the Loan-A-Tool® program.

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