You turn your keys in the ignition, feel the starter motor engage, and hear the engine settle into its familiar hum. It’s all thanks to the battery, whose number one job is to supply the electrical power that starts your engine. But how do car batteries work to generate that electricity, when should you replace it, and how do you know what battery your car needs?
In this guide, we’ll cover everything you need to know, including how car batteries work, what the different types of batteries are, and how long they last, plus how to choose a car battery that’s right for your ride.
How Do Car Batteries Work?
Like all batteries, car batteries work by converting chemical energy into electricity. Most gas-powered vehicles use lead-acid batteries to create this chemical reaction. Unlike the alkaline battery you might find in a remote control or flashlight, lead-acid car batteries generate electricity from the exchange of ions between lead and lead dioxide plates submerged in an electrolyte solution made of sulfuric acid and water. Let’s break down how exactly this works, without getting too technical.
Inside your car battery are six individual cells, each housing its own lead and lead dioxide plates in the electrolyte solution. The lead dioxide plate acts as the cell’s positive electrode, while the lead plate acts as its negative electrode. When the battery is in use, the sulfuric acid solution reacts with the plates to exchange electrons between them. During this reaction, electrons traveling from the negative battery post through wire circuits to the positive battery post create the electrical current your car needs to kickstart your engine and power accessories like headlights and windows.
The electrons released during this reaction flow out the negative side of your car battery, through your car’s electrical system, and back to the positive side of the battery to complete the circuit. The genius thing about car batteries is that the electrical current is reversible, allowing the battery to recharge by having the alternator reverse the chemical reaction that previously took place in the battery cells.
Each battery cell produces approximately two volts of electricity, which is why most car batteries are rated as 12-volt batteries. For most cars, that’s enough of a jolt to get the engine started or power your car’s electronics for a few hours when the engine is off.
How Long Do Car Batteries Last?
On average, car batteries last about three to five years, but battery health is much more than just age. External factors such as harsh climates, frequent short trips, and parasitic draws will shorten battery life.
If you’re not sure how old your car battery is, pop your hood and take a look. Your battery will likely have a sticker with its manufacturing date either on top or on the side of the battery case. Once your battery turns three years old, it’s a good idea to have it checked yearly. Fortunately, peace of mind doesn’t have to be expensive. At Firestone Complete Auto Care, we offer a free battery check with every visit.
Car Battery Types Explained
The type of battery you put in your car can have a big impact on your vehicle’s performance, longevity, and most importantly, whether or not your car will start. If you're wondering "what are the different types of batteries," three common categories include: lead-acid batteries, AGM batteries, and lithium-ion batteries.
Lead-Acid Batteries
Lead-acid batteries are the most widely used automotive batteries and typically come in two varieties: flooded or sealed. Flooded lead-acid batteries are filled with a liquid electrolyte (sulfuric acid and water) necessary to generate electricity, whereas sealed lead-acid batteries use the same electrolyte but are built to be leak-proof.
Flooded lead-acid batteries are a reliable, cost-effective option for powering your car, but they do require some maintenance. Namely, topping up the electrolyte solution with distilled water to prevent the buildup of lead sulfate, which can lead to internal corrosion and reduced battery life.
Lead-acid batteries are best for budget-conscious drivers who need a dependable battery for everyday driving. They may not be the best choice for people who only drive occasionally or for high-tech modern vehicles with high electrical loads.
- Lifespan: 3-5 years
- Best Suited For: Budget-conscious drivers who drive daily and don’t mind some light maintenance.
Absorbent Glass Mat (AGM) Batteries
Absorbent glass mat (AGM) batteries get their name from the use of fiberglass mats that absorb the electrolyte solution in each battery cell. Though the internal chemistry of AGM batteries is similar to standard lead-acid batteries, AGM batteries offer some distinct advantages.
Because they are sealed and have the absorbent fiberglass mat inside, AGM batteries are virtually spill-proof. That also means drivers don’t have to worry about topping up battery fluid. Additionally, AGM batteries offer better resistance to road vibrations, faster recharging, and a longer life. The trade-off is that they come at a higher price point—as much as 40-100% higher than standard lead-acid batteries.
AGM batteries are best suited to keep up with the higher energy demands of modern vehicles, especially vehicles equipped with start-stop systems. They also deliver more reliable performance for drivers in hot or cold climates, those who make frequent short trips, and in off-road vehicles.
- Lifespan: 3-7 years
- Best Suited For: Drivers who want a higher-performing, maintenance-free battery and don’t mind the extra cost.
Lithium-Ion Batteries
Lithium-ion, or li-ion, batteries have made their way to the mainstream thanks to the rise of hybrid and electric vehicles (EVs). These are the same kind of rechargeable batteries found in things like cordless power tools and laptops, but on a much larger scale. Virtually all EVs run on lithium-ion batteries.
Li-ion batteries are known for their long life and high energy density, meaning they can store more power in a smaller space. Compared to lead-acid batteries, Li-ion batteries are lighter, more efficient, and maintenance-free.
Despite their long lifespan and more efficient performance, lithium-ion batteries are rarely seen in conventional cars due to design compatibility issues. What’s more, their higher price isn’t typically justified when lead-acid and AGM batteries offer more than enough reliability for gas engines.
- Lifespan: 8-10 years
- Best Suited For: Hybrid and electric vehicles
How to Know What Battery Your Car Needs
Choosing the right battery for your car comes down to understanding the specs for your specific make and model, and the driving conditions it needs to perform under.
Understanding Battery Specifications
Before purchasing a new battery, check your owner’s manual and make sure it meets the needs of your make and model according to the standard battery measurements listed below:
- Group Size: a measure of the battery’s size dimensions, voltage, and terminal locations necessary to correctly place the battery in your vehicle.
- Cranking Amps (CA): a measure of the battery’s ability to start the engine (or crank) at 32ºF.
- Cold Cranking Amps (CCA): a measure of the battery’s ability to start the engine in extreme cold (0ºF)
- Reserve Capacity: the amount of time, in minutes, that a battery can deliver consistent voltage (around 25 amps) before it can no longer power your vehicle and needs to be recharged.
How to Choose the Right Car Battery For You
To choose the best battery for your car, consider the type of vehicle you drive, the climate you drive in, and your own driving habits.
Vehicle Type
Newer cars, as well as high-end luxury vehicles, tend to require more battery power to run modern features such as start-stop systems, high-tech safety monitoring, and powerful infotainment displays. If you have all the bells and whistles and don't want to worry about your car not starting, a high-performing AGM battery may be the way to go. If you're rolling in a 15-year-old Honda Civic and just want something that works, a reliable lead-acid battery will work just fine.
Climate
If you've ever had trouble starting your car on a cold morning, you know climate affects battery performance. Living in areas with either extreme heat or cold will take a toll on your battery life, so you'll want to prepare with an AGM battery, or even a sealed lead-acid battery for a more cost-friendly option.
Both of these battery types are less susceptible to the outside environment, and AGM batteries in particular often deliver more power on ignition. For cold winters up north, make sure you get a battery with high cold cranking amps (CCA) to ensure your car always starts in frigid temperatures.
Driving Habits
Lastly, consider your day-to-day driving habits. Do you only use your car occasionally, or make frequent short stops? You’ll want a longer-lasting AGM battery that doesn’t discharge too quickly without use. For daily commutes and long hours in the car, or for drivers who simply don’t want to spend a lot of money, a standard lead-acid battery will likely get you where you need to go.
Car Battery FAQs
Can a Bad Battery Affect the Starter?
Yes. When your battery starts failing, your starter motor may have to work overtime to get your vehicle to start. On top of having to work longer, your starter can overheat if cranking for too long.
Pro Tip: Don’t leave your car’s power up to fate. Our Electrical System Check makes sure all the necessary parts are working properly. We’ll know right away if any weak parts may need immediate replacement.
Can a Bad Battery Affect the Alternator?
Yes. A battery that isn’t producing enough voltage may cause your alternator to continuously run at full output. Most alternators are not designed to do this and may overheat, thereby shortening their lifespan.
What Are the Symptoms of a Bad Car Battery?
These are some of the most common warning signs of a failing car battery:
- Slow engine turnover or clicking
- Dim headlights and electronic issues
- Check engine and other indicator lights
- Low battery fluid level
- Bloated battery case
- Sulfurous smell
Where Do I Take Old Car Batteries?
The best place to take your old car battery is your local Firestone Complete Auto Care. Our professional technicians will take care of handling, transporting, and recycling your old battery.
Get the Right Battery For Your Ride
Powering your ride is a complex affair. But here’s a straightforward fact: you need a functioning battery to make it go. Ensure that your battery is in top condition with Firestone Complete Auto Care. We offer free battery tests with every visit, and our skilled technicians can help you find the right battery for your vehicle if you need a new one. Schedule your appointment at your local Firestone Complete Auto Care today!
