The Ultimate Guide to Car Batteries

The automobile powered by fuel instead of trained animals has been around for more than two centuries now. Karl Benz was the first to introduce the horseless carriage. But it wasn’t until the Model T Ford that a large portion of the population got to experience it and understand its viability. Would you believe that it had fake wooden hands as indicators?

We have come a long way since then, with cars in various shapes and sizes that can suit almost any terrain. You can even look at variants like the Gibbs Aquada that can run on water as well as land. Yet, all those variants have one component that remains persistent: batteries. Whether you own an eco-friendly Toyota Prius or drive the blistering BMW M2 Competition, it has a battery to power its electrical systems.

That’s why it’s crucial to understand how this integral part, what some would say is the heart of the engine, functions. To that end, here is the ultimate guide to car batteries that can assist with understanding all aspects in Layman’s terms.

Table of Contents

What Are Car Batteries Made Of?

A car battery is made up of the following components.


It is where the charge of the battery is stored. Most batteries use a solution of sulfuric acid and water as an electrolyte. In recent years, there have been viable alternatives in the form of gel and Li-ion batteries. More on them later.


The electrodes interface with the external circuit to provide definite positive and negative terminals. They are usually made of a metal alloy.


Since a car battery consists of several cells, there need to be structural features separating them so that they don’t react with each other. Separators are thick insulation plates that allow the cells to remain connected without shorting out.

Protective Case

The external case houses all the components mentioned above. It should have a sturdy design to keep the external elements at bay while allowing easy access to the parts without specialized tools.

What Does a Car Battery Do?

A car battery has two primary functions, as detailed below.

1. Energy for Ignition

The electrical energy from the car battery gets transferred to the engine’s ignition when you start the car. As soon as you press the button or turn the key, the circuit is complete, and a current flow to the ignition. This is higher in magnitude since it has to burn the initial fuel on its own. After a few seconds, it returns to a lower state as the engine goes into a running state.

2. Powering the Car’s Systems

Your car battery supplies electricity to other parts and accessories in your car. Everything electrical in your vehicle is powered by the battery, from headlights to climate control. Of course, none of these systems are connected directly to the battery. There is a controller that assigns the proper voltage and current to each device.

How Does a Car Battery Work?

How Does a Car Battery Work?

A car battery works on the principle to convert electrical energy to chemical energy and vice versa. It depends upon whether it is being charged or discharged. For the sake of simplicity, we’ll be looking at the most common form of battery: the flooded lead-acid battery.

In a discharging state, the lead at the anode oxidizes and loses its electrons to the external circuit. Those lead ions combine with the sulfate ions in the solution to form lead sulfate. On the cathode side, the lead oxide gains electrons and breaks down into lead and oxide ions.

The oxygen consumes the hydrogen ions in the solution to form water, whereas the lead ions react with the sulfate ions to form lead sulfate. That process gets reversed during charging.

See full this video: How A Car Battery Works 

What Does the Battery Warning Light Look Like? (And What Does it Mean?)

A warning light comes up on your car’s dashboard when the alternator is no longer charging the battery. The warning light usually glows bright red or yellow to grab the driver’s attention. Depending on your car’s make and model, you might also get an audio cue when it comes on.

That only leaves you with the remaining charge to drive your car to the nearest service station or your home. If either of them is too far away, it is best to park your car at the nearest safe place and call for emergency assistance. You can also explain your situation to the passersby who can help you jump-start your car’s battery.

Types of Car Batteries

Just as there are various types of cars, car batteries also come in different types, each with some variation to the basic structure.

Flooded Lead Acid Battery (Wet Cell)

Flooded Lead Acid Battery

It is the most common and inexpensive kind of battery available today. This is the battery that shares the same electrolyte across multiple cells. Each cell has two electrodes, typically composed of lead and lead oxide, which react with the sulfuric acid to form lead sulfate and electricity. They are pretty popular due to their low costs and the ability to recharge at a decent rate. Although, companies have tried to phase them out with concerns about the non-eco-friendly disposal and safety during a crash.

See more article: Structure of lead acid batteries

Absorbent Glass Mat Battery (AGM) Battery

Absorbent Glass Mat Battery

AGM batteries comprise several cells that store the electrolyte individually. That increases durability as the battery can function even as a few cells get damaged. The design also allows for improved seals at the terminals that reduce the electrolyte from evaporating too quickly.

Lithium-Ion (Li-Ion) Battery

Lithium-Ion (Li-Ion) Battery

Most prominent with electric vehicles, Li-ion batteries contain a solid electrolyte that exchanges electrons through lithium atoms. The cathode is usually made of a nickel-cadmium alloy that obtains the electrons from the circuit. Due to its modular design, a lithium-ion battery offers plenty of flexibility with its shape and size.

See more article: Top 5 Best Lithium-Ion Battery

Silver-Calcium Battery

Silver-Calcium Battery

Silver-calcium batteries are a variation of lead-acid batteries that contain electrodes made from lead-silver-calcium alloy. That increases the battery life by resisting the effects of corrosion and ion degradation using silver and calcium ions. While it delivers an extended lifespan with minimal maintenance, the effect can wear off quickly if the battery is not charged regularly.

Enhanced Flooded Battery (EFB)

Enhanced Flooded Battery (EFB)

The most suitable battery type for hybrid vehicles, EFBs utilize carbon additives to the negative electrode and a chemical paste on the positive electrode, respectively. It prolongs the life cycle of the battery while also reducing the overall weight. Since the carbon can dissolve into the electrolyte, it accelerates the electron transfer, allowing for faster recharging through the alternator and regenerative braking in hybrid electric vehicles.

Gel Cell Battery (Dry Cell)

Gel Cell Battery (Dry Cell)

Mostly known for solar cell applications, gel cell batteries have a high number of recharging cycles. You can obtain as many as 5000 with zero maintenance. Moreover, the battery can discharge down to zero volts without affecting the capacity of the battery. Gel cell batteries are often the most expensive compared to any other battery with similar capacity.

Deep-Cycle Battery

Deep-Cycle Battery

Batteries designed to be discharged close to zero without affecting their charging performance are called deep-cycle batteries. AGM, gel, and a few lithium-ion batteries are deep-cycle batteries. A few lead-acid batteries with valve regulation also come under this category. In such batteries, the lead electrodes are infused with antimony to increase the life cycle.

Nickel-Metal Hydride Battery

Nickel-Metal Hydride Battery

This type of lithium-ion battery utilizes a cathode with a nickel and metal hydride. It is similar in almost every other way to a Ni-Cd battery, except with a higher energy density and up to three times the capacity. Depending on the application, the hydride metal can be cobalt, manganese, or aluminum.

Benefits of Using a Good Auto Battery

Benefits of Using a Good Auto Battery

Choosing a good auto battery can yield several benefits in the long and short term. Some of the most significant ones include the following.

  • High energy density: The appropriate battery supplies enough energy to power the engine and all the electrical equipment you need in the car.
  • Reduced maintenance: When availing of an adequate car battery, you can drive around carefree without popping the hood and checking the terminals regularly.
  • Fast charging: An excellent car battery charges up really fast. The feature is especially crucial in electric vehicles, where you can wait hours for the wrong battery to charge up.
  • Lightweight: A battery has a significant weight to manage along your vehicle’s chassis. Using the correct battery can keep your car lightweight, increasing its efficiency.
  • Low discharge rates: You keep your car inoperative for more than 90% of its ownership time. As such, you may want to go for a battery that has a low discharge rate. That way, you can ensure you have enough energy to start your vehicle when needed.
  • Longevity: The correct battery type has a decent life cycle, which you can utilize with minimal maintenance.

Key Features of a Car Battery Label

Key Features of a Car Battery Label

If you’ve ever observed the car battery label, there are several symbols and abbreviations that may be hard to understand. Still, they often contain valuable information that can harm your vehicle if you get it wrong. The essential parts include the following.


The voltage is the cumulative potential difference of the entire battery. While a battery is rated for a set voltage, it helps to always go with a more powerful variant. For example, if your car is rated for 12 Volts, you should prefer a battery rating of at least 12.2 Volts.

Cold Crank Amps (CCA)

CCA measures the current available at -18°C (-0.4°F). CCA is a crucial criterion in considering whether a battery will remain effective in freezing or snowy conditions. It is usually rated with a single number. For instance, a CCA 250-rated battery can deliver 250 A of current for 30 seconds at -18°C.

Cranking Amps (CA)

Cranking amps denote the magnitude of current that a battery can sustain for 30 seconds at room temperature. It is usually 20% more than a battery’s CCA rating with the same measurement method.

Reserve Capacity (RA)

Reserve capacity helps determine the current density of the battery. It is the duration for which it can sustain a 25-Ampere current at 26.6°C (80°F) till the battery is discharged down to 10.5 Volts.

Amp-hours (Ah)

It is the amount of energy charge a battery can deliver consistently for one hour. The higher the Ah value, the more capacity a battery has in its customary usage conditions.

Deep Cycle

It is a rating that tells you that you can discharge a battery to 25% or lower before it needs recharging. Deep cycle batteries usually have high recharging cycles and can function for longer without requiring maintenance.

Date Code

The date code lets you know the acceptable period of use for a battery. Think of it as an expiry date. Past the date code, the battery may be susceptible to a lowering in efficiency, leakage, or even an explosion during charging.

Group Size

You can determine the size of your battery by examining its group size. Keep in mind that American, European, and Japanese group sizes have plenty of differences. So, match the one that’s rated for your vehicle, which might be present in your car’s owner’s manual.

What Should You Consider When Buying Car Batteries?

What Should You Consider When Buying Car Batteries?

It is essential that you buy your car battery right the first time. It avoids multiple trips to the electrical store while also keeping you safer on the road. Below are a few tips that can help you achieve that.

Check the Owner’s Manual

The owner’s manual contains all the information necessary for choosing the correct battery type. So, try to obtain one that best matches the configuration. The second best option is going just above the stated specifications.

Find Your Battery Group Size

Your battery group size can differ depending on where your car was manufactured. The correct battery size fits snugly into the bay, avoiding vibrations and movement during your commutes. There are three primary group sizes for car batteries: Side-Post (American), Recessed Top Post (European), and Standard Top Post (Japanese).

Power Requirements

Find the required minimum CCA (Cold Cranking Amps) and CA (Cranking Amps) to determine how likely your car can start in specific conditions. A higher value can keep your car’s electronics functional for a more extended period, but it can also drain the battery quicker. So, it helps to stick to the labeled rating as much as possible.

Determine the Battery Cell Type

The nature of the car battery cells affects various factors. There are several variations with just lead-acid batteries, from regularly flooded to AGM. In best-case scenarios, using a battery with a cell type your car is not designed for can lower its efficiency. In the worst case, that can lead to a severe accident down the line.

Reserve Capacity

When buying a new car battery, the reserve capacity can help you choose the one that can have your back when the engine is not running. It can help you get out of hostile situations such as alternator failure or leaving your parking lights on for a long.

Battery Freshness

The manufacturing date affects the batteries’ effectiveness, as they start discharging right after the terminals are inserted. Thus, you should get a recent one off the shelf. Many stores like Target and Costco often put up deals for batteries that are six months or older within the stock.

Type and Position of Terminals

You have to connect the car battery in a way that it stays stable when you drive the vehicle. Any loops or tensions in the cables can short the circuit or cause an electrical fire. Therefore, check the type and position of the terminals to ensure that you buy the battery that fits your vehicle configurations.

Battery Life

A car battery should sustain your car for some time before needing maintenance or replacement. Still, some variants have a longer battery life than regular lead-acid ones. Sure, they may be more expensive, but you save on overall costs if you’re not someone who changes their cars alongside their phones.

Ampere-hour (Ah)

The Ah rating determines the battery capacity in practical terms, which is why you should go for the one that maximizes it. Simultaneously, try to stick to the acceptable voltage and CA/CCA ratings that are mentioned in the owner’s manual.


You can avoid a check every few months to ensure that they are running in an acceptable state. So, prefer the ones that have a zero maintenance rating. AGM or Li-ion batteries are often the best for avoiding such chores.

Battery Brand

A few battery brands stand out in quality, recycling policy, and availability. Select the one with distinctly positive user reviews, and the battery type best suits your vehicle requirements.


Battery warranty terms can vary from only manufacturing defects to replacement on accidental usage. That is why you should read the warranty terms carefully before confirming your purchase. If you’re not suitable with the terms, you can ask the retailer for modifications or switch your battery brand entirely.

Tips for Keeping Car Batteries In Good Condition

Tips for Keeping Car Batteries In Good Condition

Once you’ve installed the battery, there are a few tips you should remember to keep it in optimal condition. You can even stretch past the rated lifespan of the battery using those.

Check the Expiration Date

Your battery can be hazardous to use past its expiration date. It can be convenient to forget it in a few months, so keep a reminder on your phone if it’s approaching fast. It is a good practice to replace the battery every four years to ensure that you have enough juice for emergency conditions.

Routinely Test Battery Voltage

Use a multimeter to check the battery voltage every few months. Extensive drops from the rated voltage indicate that a battery might need electrolyte replacement or is about to die.

Check the Acid Level

A hydrometer can help you determine accurate acid levels within your car battery. The sulfuric acid concentration should be between 30% and 50% in flooded lead-acid batteries. In the case of AGM batteries, it comes up to around 80%.

Add Water Carefully

Over time, you may need to add water to your car battery to maintain the balance of ions and keep it functional. Although experts recommend going to a service station, you may need to do it on your own if circumstances call for it.

Use goggles to cover your eyes, and wear gloves during the entire process. The water may splash owing to the concentration and temperature differences. Thus, it is recommended to add the water using a flask.

Conduct a Battery Load Test

Similar to a multimeter, a battery load tester is a portable device that can help you conduct a reliable test to ensure that your battery is running in an acceptable state. Typically, you would need some heavy equipment only available at a retailer or a repair shop. For best results, you must conduct a full-load test every six months.

Clean the Battery

Dirt and other pollutants can clog the battery terminals or react with the electrolyte to create toxic fumes. Thus, you should keep the battery clean using specialized products. Use a soft cloth dipped in a basic cleaning solution to clean the outer surface. To prevent rust on the terminals, you can apply the same solution using a toothbrush. Moreover, cover the terminals in petroleum jelly to make it easier to connect the cables.

Keep the Cables Tied

Speaking of cables, loose ones can come off the battery and disable the circuit. You can use a few cable ties to tighten the wires along the engine bay. Additionally, you can tie them against each other to keep them more manageable and prevent contact with other components.

Don’t Leave Your Car for Too Long

When you keep your car’s lights and electronics on without the engine running, it will quickly use up your battery. Sure, it doesn’t matter if you do it for a few minutes, but leaving it on for too long can make your car battery go into a deep cycle. Repeating that can reduce the overall lifespan and maximum capacity.

Keep the Battery Warm

Low temperatures slow the flow of electrons and prevent the battery from recharging swiftly. Experts recommend keeping your car battery warm by covering it with a thermal cloth or storing it in a controlled environment when not in use.

Don’t Overcharge

Most batteries can overcharge to 120% of their capacity, but going beyond that can create hazardous circumstances. Excess charges can cause thermal instability when you connect it to your car. That can melt the insulation or cause an electrical fire.

Limit the Use of Electrical Accessories

An essential function of your car battery is to supply energy to your vehicle’s ignition system. So, avoiding blaring 3000-Watt speakers and switching on neon lights would be excellent, especially when you don’t need them.

Spot Issues

Many service centers like Walmart car care can examine your car battery free of charge. Therefore, if you have some spare time, it helps to pull over to one and have your car battery checked. More so when they’re present along your route. A professional eye can highlight the issues you would otherwise miss and fix them on the spot.

Choose the Best Car Battery

You can make the most of your car battery if you source it from a reliable manufacturer. A few offer zero-maintenance batteries that you don’t have to check up on too often. Others can offer free repairs or replacements for an acceptable period, should you run into any trouble.

Don’t Delay Car Battery Replacement

You must not wait until the rated five years have expired to replace your car battery. Get your current one thoroughly tested at least four months prior to the rated date, regardless of how well you’ve maintained it. If you detect even a single significant problem, it is best to replace it now than to deal with an expensive repair afterward.

See full this video:  Tips for Keeping Car Batteries In Good Condition

Lead Acid Batteries vs. AGM Batteries vs. Lithium-Ion Batteries– Which Is Better?

Now that you’re aware of the various battery types let’s compare the top three most widely available against each other. Here’s a table to make your job easier. Remember that the comparison is for a standard 12-Volt battery with a 100 Ah capacity.

Criteria Lead-Acid Battery AGM Battery Li-Ion Battery
Cost (Varies by brand) Around $120 At least $180 At least $250
Reliability Less reliable due to the high chance of electrolyte leakage and terminal degradation Highly reliable, can function with multiple cells damaged. Sound structural design and limited leakage make it highly reliable
Average Life Span 5 years 10 years 15 years
Reserve Capacity Low Moderate High
Maintenance Requirements Requires regular maintenance and checks Doesn’t require regular maintenance but checks help ensure the integrity Zero maintenance
Ease of Recycling Convenient to recycle, even with immense damage Can be recycled if the outer case is unharmed Only a few specialized sites can recycle
Availability Easily available both online and in stores Easily available in stores, but you may have to order online to fit the specifications Only available online per vehicle specifications
Safety Quite rugged, but still the least safe battery option Isolated cell structure makes it stronger against vibrations and impacts High thermal stability and crash-resistant design make it the safest option

See more article: AGM vs Lithium Batteries: Which One To Choose According To Your Needs?

The 3 Popular Car Batteries Worth Buying for Your Car

Considering that each car battery type fits a specific customer base, let’s look at a few of the best batteries from trusted manufacturers and what makes them the best picks.

Optima Batteries 8020-164 35 RedTop Starting Battery

One of the best-selling variants from Optima, the 8020 RedTop is a reliable option if you want a reliable battery without paying a premium. It is conveniently available in most Walmart and Target stores since the size 35 fits the engine bay of most cars. You can also order it from Amazon for less if you can avail of any seasonal deals. With 720 cold cranking Amps, it is suitable for both hot and cold weather. The battery comes with a 5-year warranty but can last you well up to ten years with minimal maintenance.

You can see more article: Optima Batteries Troubleshooting: How To Fix!

ACDelco Gold 94RAGM BCI Group 94R Battery

The ACDelco Gold uses enhanced paste and silver-calcium technology to increase the battery’s longevity. The calcium-lead terminals allow for maximum conductivity while providing an appreciable CCA rating. It consists of a puncture and impact-resisting case that can withstand the worst of impacts and has been verified as 100% leak-proof. It comes with a 36-month warranty, although several user reviews have claimed that it can last well after 7 years.

Renogy 12V 100Ah Lithium LiFePO4 Deep Cycle Battery

If you desire a battery that can last for decades as you roam in your RV or SUV cross-country, then the Renogy Li-ion Deep Cycle is the ideal choice. It has a lithium-iron-phosphate electrolyte that grants it faster recharging and is capable of functioning at less than 20% capacity. It has a built-in dual-processor Bluetooth system that allows you to monitor the battery status from your phone. It saves you from having to check the battery regularly and grants real-time monitoring as you can examine the battery status with the accessories turned on.

Frequently Asked Questions

How long do car batteries last?

While the exact lifetime varies with battery type and manufacturer, ca batteries can usually last about five years. However, keeping up with the maintenance can allow you to get up to 10 years from AGM batteries. A few lithium-ion batteries can last well past 20 years.

Can I change a car battery myself?

Yes. Swapping out a car battery is pretty straightforward. You must disconnect and reconnect the terminals once the new battery is in place. Just ensure to exercise adequate safety measures during the process.

How do I know if I need to replace my car battery?

There are a few telltale signs that let you know whether your car battery requires replacement:

  • Engine not starting or taking too long to start
  • Lights going dim during use
  • Air conditioning going damp or not available at total capacity
  • Foul smell and fizzles from the terminals
  • Formation of rust at the battery case or cables

How do I avoid running down my car battery?

Your battery runs down when the charge consumed by the electrical system doesn’t get replenished by the alternator fast enough. Thus, you can avoid running down your car battery by not leaving it idle for a long time or using the electrical accessories without starting the engine.

Why has my car battery died?

Your car battery may be dead for any number of reasons, as mentioned below.

  • The battery charge has depleted entirely and thus cannot be recovered by the alternator.
  • The concentration of electrolytes has fallen beyond variable levels.
  • A leak has emptied the electrolyte from the battery
  • One or more terminals have been covered in rust or non-reactive substances like lead sulfate.

What do I do if my car battery dies?

Get your dead car battery examined at the nearest service station. A professional can tell you whether it’s more viable to replace it or send it for repairs.

How do I dispose of a used car battery?

Most car batteries can be recycled, provided the outer case doesn’t sustain too much damage. So, you can give it in for a new one at a battery exchange station like Walmart to get a discount on your new battery. However, if the battery is entirely beyond repair, you must dispose of it at specialized waste-management centers, usually located close to used car lots.

How do you disconnect your battery?

You have to remove the connectors from both terminals of the battery. The safest way is to wear insulating gloves and ensure that the ignition is turned off. Remove the negative one first.

What do I do about a dead battery?

You can revive a dead battery by refilling it with a fresh electrolyte and swapping out the terminals with new ones. That is often viable at your nearest battery repair shop, but most people just buy a new battery since that is more economical.

What voltage is a car battery supposed to be?

Most family saloons can run relatively efficiently with a 12-Volt car battery. Still, it is best to check the precise voltage of your particular car from the owner’s manual.


And that concludes our ultimate guide to car batteries. We hope you learned enough to buy, install, and maintain the most suitable battery for your vehicle. Remember that no matter what the company advertises, there are always variables with the usage and location. So, keep that manual and multimeter handy. You never know when your car battery might start showing signs of degradation out of nowhere.


  1. Starter Battery Silver, 12 V, 72 Ah
  2. How A Car Battery Works
  3. Key Features of a Car Battery Label
  4. AGM vs Lithium Batteries: Which One To Choose According To Your Needs?
  5. How A Car Battery Works – basic working principle

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