Vehicle battery types. How the Battery Provides Power

Car Batteries Guide: Components, Types, and Functions

The batteries are an essential component of any vehicle; they are the power storage components of the car. Whether a fuel engine or an electric vehicle, you can only start the car if the battery is functioning. The batteries are more than a regular box, they store energy. So, upon ignition, they release the stored energy, allowing the car to function. In this article, we will discuss parts of car batteries in detail.

A battery refers to any device that converts chemical energy to electrical energy. The car or automobile battery stores chemical energy but immediately converts it to electricity upon ignition.

The typical car battery is rechargeable and designed to be a wet-cell battery. Regardless of the car type, all batteries perform similar operations – power the vehicle and all its electrical components.

When you start your car, the battery supplies electric current that initiates the internal chemical engines needed to drive the car. In addition, other electronic parts of the vehicle, like lights, radios, wipers, etc., require the battery to function optimally.

Components of a Typical Car Battery

A typical automobile battery is enclosed in a battery box or case. However, the interior parts of the car battery consist of different components. Below are the essential car battery parts.

Battery Acid

The acid is a solution of sulfuric acid and water (36 to 40 percent). The resulting mixture serves as the electrolyte that triggers the chemical reaction, which produces the electric current that powers the vehicle. It is often of high purity, as the presence of contaminants may alter its effectiveness for car power generation.

The acid and water react upon igniting the car, producing the suitable voltage needed to kick-start the vehicle. The voltage produced will be insufficient for driving the car engine if the battery is weak.

Battery Terminal

It is also called battery bushing. The battery terminal is the connection point linking the battery with the car’s electrical components. Like any electrical device, it has two terminals – the positive and negative straps of the battery end cells.

Battery Case

Both fuel and electric vehicles have parts of the batteries enclosed within a box. The case protects the contents and parts of the car battery. For fuel batteries, cast-on-straps are often designed with polypropylene resins. In EVs, the battery enclosure box is usually created with aluminum alloys. The battery case offers protection for its contents and minimizes the impact effects on the battery, thereby extending its life.

Battery Plates

A typical car battery consists of negative and positive plates. Either plate consists of a metal grid, though the positive end contains lead dioxide material, with the negative end having a spongy lead. Either plate has a cast-on strap on top, linking each component to the battery cells.

Battery Separator

As the name indicates, the separator creates a distinction between the positive and negative plates. Also, it is often made of polyethylene or other plastic polymers.

Working Principles of Car Batteries

The primary function of the automobile battery is to provide the electric current required for powering all the vehicle’s electrical components. Even when the car is turned off, it gives enough energy to power some elements, such as the lights and radio. However, it’s only possible to drive the car after igniting it.

Here is what happens when you start your car.

First, a chemical reaction occurs in the battery, causing it to transform chemical energy into electrical energy for powering the vehicle and providing voltage to the car starter.

The battery then starts a stabilizing action – it keeps the electric current in a steady state by regulating voltage. If voltage is unregulated, current continues to develop, which may cause adverse and harmful reactions in your car.

Note, only about three percent of the battery capacity is required to start a car. Therefore, most automobile batteries just deliver maximum electric current for a short while to power the engine and other electrical aspects of the car. The batteries are sometimes called SLI – starting, lighting, and ignition because they are the device’s main functions.

Our Review Standards

To select the car batteries featured in this buyers guide, our team first combed through dozens of resources such as DIY mechanic and auto enthusiast forums, manufacturer and auto battery-specific websites, instruction manuals from manufacturers, and reviews from online retailers. We pay particularly close attention to quality reviews and recommendations that highlight the quality of warranties, customer service support, build quality, materials, and overall reliability. We also factored in the quantity and quality of online retailer reviews from websites such as Amazon, RealTruck, Advance Auto Parts, and more. We looked at factors such as standout customer reviews, prices, meaningful superlatives, and discount shipping eligibility.

Why You Can Trust Us

Since 2020, we have published over 200 auto product reviews in an effort to make shopping for auto products easier. Our team of writers, editors, researchers, and product experts collaborates to thoroughly vet top products. We try to perform in-house testing on real vehicles whenever possible before making our recommendations. When testing is not feasible, however, our aim is to make your life easier by doing all the online research for you and presenting that research in the form of easy-to-read product comparisons and buyers guides, rather than outright recommendations. For more information on our testing methodology and how we evaluate every product, check out our methodology page here.

Best Car Battery: Buyers Guide

Battery Type

There are a number of different car battery technologies out there. Standard lead-acid (SLA) and absorbed glass mat (AGM) batteries are the most common. Lithium-ion batteries are also becoming more common for cars.

  • Standard flooded lead acid : This is the most common type of car battery. The battery contains liquid battery acid and will require more maintenance than an AGM or lithium-ion battery. This type of battery is most common in older vehicles (pre-1980).
  • Absorbed glass mat : An absorbed glass mat battery is highly vibration-resistant, non-spillable, and maintenance-free. Battery acid is absorbed in fiberglass mats, which prevents leakage or spillage. This type of battery offers a superior lifespan to standard flooded batteries and can handle large power demands. It is the most common type of car battery in modern vehicles.
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  • Lithium-ion : Lithium-ion batteries can be much smaller and lighter than AGM and SLA batteries. They offer a very fast charging rate and are maintenance-free. This type of battery tends to outlast AGM batteries.

Choose a battery type that matches your existing battery. AGM batteries are the most common type of car battery. If you replace an AGM battery with an SLA battery, your car may not start or function properly.

Group Size

Your car battery rests in a specifically sized battery box. If your replacement battery is too small, it won’t be properly secured. If it is too big, it won’t fit in your vehicle. In addition to battery dimensions (length, width, and height), terminal location is also critical to proper fit.

Fortunately, you won’t need to get out the measuring tape to match battery dimensions. All batteries should have their group size listed somewhere on the label. This is typically a two-digit number. You can also check your owner’s manual, which may list the group size, or try searching Google for your group size based on your vehicle’s make, model, and year.

Below are some common group sizes:

Cold Cranking Amps (CCA)

CCAs refer to a battery’s ability to turn a cold engine. The higher the CCA, the more powerful the battery. As with group size, your current battery’s CCA should be listed somewhere on the battery label.

Each car is engineered with the factory battery CCAs in mind, which is why it’s a good idea to match the CCA of your current battery – rather than attempt to “upgrade” your battery to one with more CCAs, as this can lead to decreased battery life.

Reserve Capacity (RC)

Reserve capacity refers to a battery’s ability to keep essential car accessories powered after a vehicle’s alternator fails. With more and more cars using computers and battery power for essential systems, RC has become an important battery feature.

As with CCA, try to match your new battery’s RC with the original battery. If you choose a new battery with a lower RC, it could fail to properly power your car’s critical systems.


Once you’ve found batteries that match the specifications of the one you are replacing, consider batteries with longer warranties. These are guarantees that you won’t have to shell out for a replacement within the warranty period.

Most car batteries come with at least a one-year warranty, but some offer warranties up to three or four years long.

Car Battery Replacement Tips

If you need to replace a dead battery, you can take it to an auto mechanic for diagnosis. A mechanic will have the tools to diagnose and quickly change your car battery. Labor costs for battery replacement can range from about 37 to 47, according to RepairPal. That said, those costs don’t account for the type of battery you’re purchasing.

If you’d prefer to change your own car battery, this is possible for a layperson, though it can be an involved procedure. Specifics may vary from vehicle to vehicle, as battery positioning is not the same for every car. Search for guide videos specific to your vehicle’s make and model or start with our general guide on how to disconnect a car battery.

Whichever type of car you have, there are some tips to keep in mind when performing an at-home car battery replacement.

vehicle, battery, types, power
  • Put safety first. Modern AGM and lithium-ion batteries are mostly safe to handle, but SLA batteries can slosh highly corrosive acid that will damage your skin and eyes. Wear proper safety equipment including goggles, long sleeves, and gloves when handling a car battery. It’s also a good idea to keep some baking soda handy, as it can be used to neutralize any spilled battery acid.
  • Keep your car’s memory alive. Modern vehicles are highly dependent on computers to operate major and minor systems. When you disconnect your car battery, it can turn off the computer, effectively resetting the onboard computer. This can cause some systems to work improperly until they are reset. Some cars will reset automatically after a few weeks, while others may require hours of diagnostic fiddling to restore. You can prevent this hassle by using a power supply cable to keep your computer powered while you replace the battery.
  • Be gentle. Don’t attempt to smash or roughly shove your battery into place. The same goes when attaching the terminal clamps. If your terminal clamps are too tight, use a terminal spreader to widen battery terminals rather than banging on your battery to force them down.
  • Recycle. Car battery recycling must be done at specific locations. Check your city website to find guidelines on hazardous waste disposal. Many offer dropoff or pickup services. You can also recycle old batteries at certain stores. Advance Auto Parts and AutoZone both offer battery recycling services. These stores also offer free battery testing.

How Much Should Car Batteries Cost?

Newer car batteries that have higher CCAs and use advanced technology are going to cost more than replacement batteries for older vehicles. While more expensive, these batteries also tend to last much longer, so can be cheaper in the long run.

In general, you can expect to pay anywhere from 150 to 500 for a new car battery. SLA batteries are usually the least expensive, followed by AGM batteries. If you choose a lithium battery, you might pay upward of 450,000.

Depending on the CCA, RC, and group size, the same model battery can vary in price up to 100.

Why Do Car Batteries Go Bad?

Car batteries fail due to multiple factors ranging from neglect to old age. Below are a few examples of what causes batteries to die.

  • Temperature : Climate is probably the greatest opponent your car battery will face. Even the best car batteries can struggle to crank in extreme temperatures, so more temperate climates typically mean a battery lasts longer.
  • Minimal Use : Having a car sit idle for a few weeks or months will usually result in a dead battery. That’s because it is not utilizing enough of the car’s charging system, which depends on the car running, to recharge.
  • Vibrations : If a car battery is not properly secured in the engine bay, vibrations from the vehicle can cause it to deteriorate and shorten battery life.
  • Corrosion : Corrosion occurs as chemicals naturally escape from the car battery and mix with air and water in the engine bay. As corrosion accumulates, it can weaken the connection of the battery terminals.

If your car battery failed within two to three years of purchase, check the parts store’s replacement warranty, they may offer a free replacement. For details on how long car batteries last, check out our informational guide.

How do electric car batteries work?

The energy storage system in electric cars comes in the form of a battery. Battery type can vary depending on if the vehicle is all-electric (AEV) or plug-in hybrid electric (PHEV). Current battery technology is designed for extended life (typically about 8 years or 100,000 miles). Some batteries and can last for 12 to 15 years in moderate climates, or eight to 12 years in extreme climates. There are four main kinds of batteries used in electric cars: lithium-ion, nickel-metal hydride, lead-acid, and ultracapacitors.

Types of electric car batteries

Lithium-ion batteries

The most common type of battery used in electric cars is the lithium-ion battery. This kind of battery may sound familiar – these batteries are also used in most portable electronics, including cell phones and computers. Lithium-ion batteries have a high power-to-weight ratio, high energy efficiency and good high-temperature performance. In practice, this means that the batteries hold a lot of energy for their weight, which is vital for electric cars – less weight means the car can travel further on a single charge. Lithium-ion batteries also have a low “self-discharge” rate, which means that they are better than other batteries at maintaining the ability to hold a full charge over time.

Additionally, most lithium-ion battery parts are recyclable making these batteries a good choice for the environmentally conscious. This battery is used in both AEVs and PHEVs, though the exact chemistry of these batteries varies from those found in consumer electronics.

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Nickel-metal hydride batteries

Nickel-metal hydride batteries are more widely used in hybrid-electric vehicles, but are also used successfully in some all-electric vehicles. Hybrid-electric vehicles do not derive power from an external plug-in source and instead rely on fuel to recharge the battery which excludes them from the definition of an electric car.

Nickel-metal hydride batteries have a longer life-cycle than lithium-ion or lead-acid batteries. They are also safe and tolerant to abuse. The biggest issues with nickel-metal hydride batteries is their high cost, high self-discharge rate, and the fact that they generate significant heat at high temperatures. These issues make these batteries less effective for rechargeable electric vehicles, which is why they are primarily used in hybrid electric vehicles.

Lead-acid batteries

Lead-acid batteries are only currently being used in electric vehicles to supplement other battery loads. These batteries are high-powered, inexpensive, safe, and reliable, but their short calendar life and poor cold-temperature performance make them difficult to use in electric vehicles. There are high-power lead-acid batteries in development, but the batteries now are only used in commercial vehicles as secondary storage.


Ultracapacitors are not batteries in the traditional sense. Instead, they store polarized liquid between an electrode and an electrolyte. As the liquid’s surface area increases, the capacity for energy storage also increases. Ultracapacitors, like lead-acid batteries, are primarily useful as secondary storage devices in electric vehicles because ultracapacitors help electrochemical batteries level their load. In addition, ultracapacitors can provide electric vehicles with extra power during acceleration and regenerative braking.

How do electric car batteries work?

All-electric vehicles have an electric traction motor in place of the internal combustion engine used in gasoline-powered cars. AEVs use a traction battery pack (usually a lithium-ion battery) to store the electricity used by the motor to drive the vehicle’s wheels. The traction battery pack is the part of the car that must be plugged in and recharged, and its efficiency helps determine the overall range of the vehicle.

In plug-in hybrid electric vehicles, the electric traction motor is powered by a traction battery pack much like an AEV. The primary difference is that the battery also has a combustion engine. PHEVs run on electric power until the battery is depleted and then switch over to fuel which powers an internal combustion engine. The battery, usually lithium-ion, can be recharged by being plugged in, through regenerative braking, or by using the internal combustion engine. The combination of battery and fuel gives PHEVs a longer range than their all-electric counterparts.

Methods of Electric Vehicle Battery Recharging

For both AEVs and PHEVs, the battery is typically charged through a standard connector and receptacle that works with any Level 1 (120 V AC) or Level 2 (240 V for residential/208 V for commercial) plug. Some Rapid charging stations use different receptors (known as SAE receptors or CHAdeMO) which are not standardized. The type of vehicle you purchase will determine the charging station you can use.

Electric vehicle batteries, solar power, and you

Charging your vehicle with electricity presents you with the opportunity to cut your greenhouse gas emissions by fueling your vehicle with a renewable resource like solar power. On average 80 percent of electric car charging is done at home, and solar panels can both offset the costs of charging a vehicle regularly and reduce the use of nonrenewable fuels in the recharging process. Additionally, many public chargers use solar panels as a way to reduce the use of nonrenewable energy throughout the process. If you’re interested in a solar panel installation plus installing a EV charging station at home, simply join the EnergySage Marketplace today and mention your interest in EV charging when filling out your profile questions.

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How the Car Battery Recharges

The alternator is responsible for recharging your car battery as you drive. This part also supplies power for your car’s electronics when you’re underway. It is driven by the alternator belt from the engine. As the belt goes around, it generates electrical current to run your vehicle’s electronics. It also sends some current back to the battery to recharge it.

A voltage regulator controls this flow of electricity to keep it even and deliver the right amount of charge to meet needs like running the AC or heater. It also protects the battery from overcharging, which can damage it.

Why Does My Battery Die?

Over the life of a battery, discharge-recharge reactions happen thousands of times. Each cycle wears out the plates a bit, and over time the lead deteriorates. As your car battery loses capacity, cold cranking amps decrease.

Deep discharging, which happens when you use the battery to run the stereo, lights or other electrical systems in your car when the engine is off, is responsible for a good portion of battery failures. Discharging most of your battery’s capacity by using it in this manner for too long and then recharging it through driving can cause the sulfur in the electrolyte solution to stick to the lead and create other damage to the plates in the battery.

What Are the Different Types of Auto Battery?

The two most common auto batteries for sale today are standard wet cell batteries and absorbed glass mat (AGM) batteries. Both use lead-acid technology. The differences are in the needs of the car.

Standard Wet Cell Batteries

These are also called flooded, conventional or SLI (starting, lights, ignition) batteries. Some standard batteries have vents that allow for airing out corrosive gases, steam, and condensation (these may be called vented batteries). They have removable caps for adding fluid. Other wet cell batteries are closed systems, with no removable caps.

  • Service needs: Occasional simple maintenance including cleaning off corrosion on terminals and topping off the fluid with distilled water if the battery has removable caps. The battery should be visually checked every year. Battery charge should be checked before road trips and after summer before temperatures fall.

Absorbed Glass Mat (AGM) Batteries

These are a type of VRLA battery, which stands for valve-regulated lead-acid. They’re sometimes called regulated valve, dry cell, non-spillable or sealed batteries. They are called sealed because they have no removable caps, don’t vent gases and can’t leak any acid. They do have pressure-activated relief valves that open only if the battery overheats during recharging.

Some newer cars, such as those with start-stop technology, require AGM batteries. These batteries will continue to deliver power to a car’s computer and electronics even when the engine isn’t running.

AGM batteries hold a charge longer than standard wet cell batteries. They can tolerate periods of disuse and repeated deep discharging and recharging cycles better than flooded batteries. They have a short recharge period but they can be easily damaged by overcharging. They also perform well in harsh climates with extreme heat or cold.

  • Service needs: Charge should be checked before road trips and after summer before temperatures fall.

Wet cell batteries and AGM batteries are not interchangeable — your car requires one or the other.

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