How To Choose Car Battery Size

‍What Does A Car Battery Do?

The battery is the electrical heart of any vehicle. Inside the unit (usually a black box), lead metal plates or cells are awash in a chemical solution. As the ignition is engaged, the battery begins a reaction between the acid and the plates, sending an electrical current to the starter, creating an electrical charge so that the engine can begin running.

A battery produces cranking amps (CCA), the amount of electrical current a battery can sustain for 30 seconds. The greater the amps, the more power the battery can provide to start and keep the car running. If you have ever had trouble getting your car to start on a frigid morning, you know exactly how important it is for a battery to be strong enough to wake your car up.

In addition to starting the engine, every electrical system on your car draws a charge from the battery; computer systems, entertainment devices, and even fuel delivery. The electrical current runs through a series of fuses and switches. When your car needs a particular part to work, the system can tap into the battery's stored power, and the car can deliver the power needed at that precise moment.

Are there Different Types of Batteries?

Yes. The automotive industry uses either one of two different batteries, and it is vital to know the difference.

Absorb Glass Mat (AGM) Batteries

They are also billed as maintenance-free, sealed, dry cell, or VRLA (valve regulated lead acid) batteries. A series of thin lead plates alternate with fiberglass mats containing an electrolyte solution. This design allows more space inside the battery compartment (more plates create more stored power). Many newer vehicles require AGM batteries, and your owner’s manual can tell you if this is the case.

An AGM battery is generally easier to maintain, safer to handle, and holds a charge longer than a wet cell battery. Because dry cell batteries have no openings (sealed), there is no danger of acid spilling out of the battery and damaging vital components. The downside is that an AGM battery can overheat due to overcharging, although most have vents to help prevent it from happening. In addition, an AGM battery will not hold a charge if it has lost all of its stored reserves, meaning you have to shell out money to replace it.

Wet Cell Batteries

Also known as flooded batteries, many cars (particularly older units) require a wet-cell battery. Specific cells inside the battery's housing contain an electrolyte solution of sulfuric acid needed to power the car’s systems. Some wet cell batteries come with removable caps or lids so that a user can add water to the chemical solution inside.

While a wet cell battery may hold a charge longer than a maintenance-free battery, the downside is that it needs to be maintained periodically. In addition, a wet cell unit is more likely to freeze or fail in significantly colder temperatures.

How Do I Know What Size Battery My Car Needs?

As you might have surmised, one battery size doesn’t fit into every car. Just like there are different sizes of household batteries (AA vs. AAA or C), a large truck with a larger engine needs more cranking amps than a subcompact with a tiny four-cylinder engine.

Knowing the Battery Group Size

A battery group size is a system used by the automobile industry to indicate the size (height x width x length) and the location of the battery posts. The battery group size consists of two numbers followed by a letter, like 24F or 58R. (Be sure to inspect the battery you are buying to ensure that the terminal posts match the ones on the unit you are replacing (if the posts don’t look similar, you have probably made a mistake).

Most auto parts stores offer free services to help you select the correct size battery, but a great place to start is with your owner’s manual. The manufacturer will have printed the battery specs in multiple locations, and you can take the information to your parts store. Another way to determine the size of battery you need is to copy the information found on the top or the side of the battery you are replacing.

Consider the Cranking Amps Needed

Cold Cranking Amps (CCA) is an essential consideration if you live in a colder climate. Exposing your vehicle to the outer temps makes the moving parts of your vehicle harder to turn, so the battery has to sustain a constant charge over a more extended period. The higher the cranking amps, the more likely the battery will be able to handle the conditions around it. Smaller vehicles only need about 150 amps, while larger cars are trucks need 400 - 600 or more.

Consider Purchasing An Original Equipment Battery

Most vehicles manufactured today have tons of electrical gadgets that require a lot of stored energy. As vehicles become more sophisticated, there is a need to increase electrical storage capacity to meet the demands. Purchasing the least expensive battery will often mean that some electrical needs won’t have the power to operate or that the increased demand will wear out the battery sooner than you need. If you have to replace your new battery a few months after replacing it, the battery can’t handle the load. Consider spending the extra money for an OE (Orignal Equipment) battery, so you can have confidence about its ability to handle everything it should.