Car Battery Buying Guide
Car Battery Buying Tips
Below are tips for getting the best battery for your needs:
Be Proactive
Being attentive to your battery’s maintenance and mindful of when it’s time for a replacement will ensure that you can choose one on your own terms, including properly researching and conveniently scheduling.
Test Batteries Annually
Inspections should be part of an owner’s routine maintenance, but it’s especially important to check before taking a long road trip.
True maintenance is largely a thing of the past. Almost all of today’s car batteries are “maintenance-free.” But we recommend having your battery load-tested by a mechanic annually once it’s 2 years old if you live in a warmer climate or 4 years old if you live in a colder climate. Doing so tests its ability to hold voltage while being used, and the results will let you know when it’s time to start shopping.
In addition, check the terminals to make sure the connectors are tight and free from corrosion.
Car batteries typically last from three to five years, according to AAA, spanning from 58 months or more in the farthest northern regions of the U.S. down to less than 41 months in the most southern regions.
The battery’s age is also a strong indicator that it’s time to consider a replacement. The date can be found on a sticker on the top or side of the battery. A battery made in October 2024 will have a numeric code of 10/24 or an alphanumeric code of K-1. “A” is for January, “B” is for February, and so on. (The letter “I” is skipped.)
A Battery Should Fit Your Car and Driving Needs
Car batteries come in many sizes. Among those that we’ve tested, there’s significant variation in which is the top performer from year to year and from size to size. This makes it impossible to make simple recommendations by brand or model. It also means you shouldn’t assume that buying the same battery model you’re replacing will get you the same results.
Make sure you get the right size and terminal locations (or type) for your vehicle. Check your owner’s manual or an in-store fit guide before buying.
In some cases, owners can replace an AGM battery with a traditional flooded one to boost longevity in hot climates, but it’s best to consult a mechanic first. Many cars come with AGMs to support an increasing array of electrical components, and the charge system may be configured specifically for an AGM battery.
Make Sure It’s a Fresh Battery
Batteries lose strength over time, even when in storage. For optimum performance, purchase one that’s less than 6 months old—3 months is even better. As explained above, most have a shipping code on the case.
Recycle Your Old Battery
A battery’s toxic lead and acid can easily be recycled, and most retailers will dispose of the old one for you. When buying a new battery at a store, you’ll probably pay an extra charge that will be refunded when you return the old battery. This serves to motivate car owners to drop off their old batteries. About 90 percent of car batteries are truly recycled, making them a recycling success story.
Compare Warranties
It’s important to choose a battery with the longest free-replacement period you can get. A battery’s warranty is measured in two figures: the free replacement period and the prorated period—which allows only partial reimbursement. A code of 24/84, for example, indicates a free replacement period of 24 months and a prorated warranty of 84 months. But the amount you’ll be reimbursed usually drops off pretty quickly once you’re in the prorated period.
Be aware that signs of neglect—such as low water levels and improper installation—can void a warranty. Heavy-duty use, such as for high-end car audio and marine applications, can also void a warranty if the battery isn’t recommended for it.
Car Battery Types
Car batteries come in two basic varieties: the more traditional maintenance-free and the more advanced absorbed glass mat (AGM).
Lead-Acid (Regular)
Batteries once required drivers to periodically top off the water in the electrolyte solution, the liquid inside that’s the battery’s power source. Modern maintenance-free batteries consume far less water than traditional “flooded cell” ones. Low-maintenance batteries retain their fluid for the life of the battery, and the caps on these models aren’t meant to be removed. There are still some batteries that can be topped off with distilled water. Properly maintained, these may last longer in hot climates.
A lead-acid battery will generally cost significantly less than an absorbed glass mat battery. But it won’t hold a charge for as long and is less able to tolerate a deep discharge.
Absorbed Glass Mat (AGM)
AGMs are built to better stand up to repeated draining and recharging cycles than standard batteries. They’re becoming standard equipment in more cars because modern features such as fuel-saving stop/start systems, electronic safety and convenience features, and power outlets for mobile electronics increase the demand for power.
But AGMs can cost 40 to 100 percent more than highly rated conventional batteries. Consider buying one if you sometimes don’t use your vehicle for long periods and the battery loses its charge. An AGM battery can tolerate a deep discharge better, and it’s more likely to fully recover if it’s accidentally drained.
“If you live in an area with extreme temperatures and are looking for a maintenance-free battery, consider getting an AGM,” says Paolo Fu, who oversees car batteries testing at Consumer Reports. “High heat can affect the life of AGM batteries, much like flooded batteries, but they tend to perform better overall in our tests.” You should replace the battery in your car with the same size and type, but you can upgrade from a traditional battery to an AGM battery.
Choosing the Right Size Car Battery
Batteries come in a variety of sizes: Group 24/24F, Group 35, Group 47 (H5), Group 48 (H6), Group 49 (H8), Group 51R, and Group 65. These numbers indicate size in the same way AA, AAA, C, and D indicate the size of batteries you’d use to power home electronics.
There are other sources to help you select the proper battery, including your owner’s manual, battery company websites, in-store guides, or your local mechanic. If you bought a used car, don’t assume it has the proper battery installed. Be sure to check with one of those other sources to identify the correct type.
Group 24F: Size 24/24F batteries fit many Acura, Honda, Infiniti, Lexus, Nissan, and Toyota vehicles.
Group 35: Size 35 batteries fit most Japanese nameplates, including many vehicles from Honda, Mazda, Nissan, Subaru, and Toyota.
Group 47: Size 47 (H5) batteries fit many vehicles from Buick, Chevrolet, Fiat, and Volkswagen.
Group 48: Size 48 (H6) batteries fit many vehicles from Audi, BMW, Buick, Cadillac, Chevrolet, GMC, Jeep, Mercedes-Benz, Mini, Volkswagen, and Volvo.
Group 49: Size 49 (H8) batteries fit many vehicles from Audi, BMW, Hyundai, and Mercedes-Benz.
Group 51R: Size 51R batteries fit many vehicles from Audi, BMW, Hyundai, and Mercedes-Benz.
Group 65: Size 65 batteries fit large cars, trucks, and sport/utility vehicles from Ford and Mercury.
How CR Tests Car Batteries
In our list of select car batteries, we show ratings for:
- Overall Score
- Cold Weather Performance: how well the battery starts an engine during extreme cold weather. We use a freezer to simulate winter conditions, cooling batteries to 0° F, and rate them based on their performance. We think that our cold weather performance test is based on more realistic charging voltages and amperage demands than typical manufacturers’ tests, and our results show each battery’s relative cranking power, regardless of a manufacturer’s claims.
- Life: how the battery performs through repeated draining and recharging. Battery life is measured by repeatedly discharging and recharging each battery about 180 times at a test temperature of about 167° F for 15 weeks or until performance drops to unacceptable levels. This simulates the hot underhood conditions a battery can face during the summer, the hardest time of year for batteries because of the heat. Frequent high temperatures are very tough on batteries, increasing plate corrosion and more quickly vaporizing the electrolyte needed for current. Long life is especially important if you make many short trips that don’t allow much time for recharging. The higher the score, the longer the battery will be reliable.
- Reserve Capacity: how long it can supply energy if the car’s charging system (the alternator, stator, and rotor) fails. It’s also a measure of how long you can accidentally leave the headlights on and still get the car started without needing a jump-start. To test reserve capacity, our engineers measure how long it takes a fully charged battery to be discharged down to 10.5 volts, which is considered to be fully discharged. At that level, the car will be unable to start without a jump-start. We consider 1½ hours of power to be average. Higher-scoring models can supply power well past 2 hours.
Car Battery Features and Accessories
These features and accessories help you get the most out of your car battery and keep it in top working order for longer.
Handle or Loop
A plastic handle or loop makes it easier to lift and carry batteries, which can weigh 25 to 60 pounds. Just as important, it aids in lowering the battery onto the tray in tightly packed engine compartments.
Float/Trickle Charger
If your vehicle is going to be idle for an extended period of time, consider having a float charger to keep it charged. Also known as trickle, storage, or maintenance chargers, these prevent excessive discharge during extended periods when your battery isn’t used. Most have built-in circuitry to prevent overcharging, although some models don’t and can damage a battery by overcharging it. Even though a float charger automatically monitors and charges the battery, it’s still best to periodically take a look to make sure that everything is still in good working order.
Jump Starter
Portable battery jump starters allow for convenient jump-starts without having to connect two cars. New, smaller models make it easier than ever to fit one in your car emergency kit. See our jump starter buying guide for more information.
Handle or Loop
A plastic handle or loop makes it easier to lift and carry batteries, which can weigh 25 to 60 pounds. Just as important, it aids in lowering the battery onto the tray in tightly packed engine compartments.
Car Battery Brands
Most aftermarket car batteries sold in the U.S. are made by three companies that build them for retailers—Clarios (formerly Johnson Controls), which supplies more than half of the market, Stryten, and East Penn. Car batteries are sold under various names and built to the specifications of retailers, so performance can vary. Most stores will test, install, and match a battery to your car’s needs. Here are the major car battery brands and where they’re sold:
