A Guide to Buying the Best Car Battery

Without the battery, modern cars wouldn’t be able to start. Unfortunately, batteries are not always reliable and are one of the most frequently replaced parts on cars. Whenever your battery fails and needs to be replaced, there are many different battery choices available to you.

To help you choose the type and battery power your vehicle needs, we have created a guide on how to select the right one based on your car type, how you use it andyour budget.

How do car batteries work?

In short, a car battery is a power bank providing the power needed to make the starter turn every time you turn the key to the START position. At each start-up, the battery is partially emptied and, when you drive, the alternator recharges the battery and takes over providing the power necessary for the proper functioning of all the onboard electrical equipment.

To avoid any start-up problem, your battery must be completely recharged by the alternator before the next start. Successive start-ups without letting the engine run for some time can quickly discharge the battery.

The working principle of car batteries

On the inside, an automotive battery consists of several accumulators connected in a series. Accumulators consist of positive and negative plates positioned in alternately and parallel, including three positive plates and four negative plates. Each accumulator produces two volts. A total of six accumulators are required per battery to produce the 12 volts needed to power most cars and motorcycles today.

These plates are then immersed in a mixture called electrolyte and are alternately connected to the positive terminal and the negative terminal. Separators are placed between them so the plates don’t come into contact with each other and cause a short circuit.

To obtain the chemical reaction which will allow to store power and make it circulate, three elements come into action: lead, water, and sulphuric acid.

The assembly is mounted in polypropylene tanks to withstand the heat produced by the engine, harsh winter conditions and the acid itself. A valve is frequently placed on the battery housing to allow the gases produced by the chemical reaction to escape without causing positive pressure inside the casing.

Different types of car batteries

Before heading to a garage or car shop to get your battery replaced, it’s important to understand the main types of batteries and their respective characteristics. Not all batteries are the same and the original battery installed on your vehicle is not always the best choice.

Here are the pros and cons of four different types of car batteries.

Open type lead-acid battery
Open-type battery
Maintenance-free lead-acid battery
Maintenance-free battery

1. Lead-acid batteries

These batteries are the most commonly used by car manufacturers due to their low manufacturing cost and their relative reliability. The average energy yield of lead-acid batteries is 75 percent. This means that 25percent of the electrical energy is dissipated during the charging, discharging and self-discharging phases.

Pros

  • Cheap
  • Reliable
  • Relatively long lifespan

Cons

  • Heavy
  • Sensitive to cold
  • High risk of leaks
  • Not suitable for motorcycles and boats

To optimize these batteries and extend their life expectancy as much as possible, deep discharges should be avoided and they should only be stored when completely charged.

AGM car battery

2. AGM batteries

The acronym AGM stands for Absorbed Glass Mat. This means that the electrolyte, consisting of 70 percent water and 30 percent acid, is absorbed or stabilized inside fiberglass blotters. These blotters, known as boron-silicates, are wedged between the plates. Unlike with open batteries, AGM batteries do not require the addition of distilled water.

This type of battery is much more tolerant of handling errors and is less prone to leaks than AGM batteries. Their hydrogen emission rate is less than four percent and complies with the most recent safety standards. Many manufacturers choose to use an AGM battery on their vehicle because it’s highly resistant to shocks and vibrations, especially when compared with other common battery types.

Unlike standard batteries, AGM batteries can be fully discharged without any significant damages. It should be noted that, even if it supports deep discharges quite well, this type of battery may be damaged if left discharged for an extended period.

Finally, AGM batteries do not require any electrolyte level adjustment. No matter the type of regulator chosen, its charging voltage is always the same as a conventional lead-acid battery. In other words, AGM batteries are compatible with any type of installation.

AGM batteries are more affordable than GEL batteries but significantly more expensive than their conventional lead-acid counterparts.

Pros

  • Increased capacity
  • Much more resistant to cold
  • No loss of water whatsoever
  • Longer lifespan than a GEL battery
  • Lower self-discharge rate
  • No risk of gas release outside the battery
  • Easy to transport since the acid is contained in the blotters and not in the liquid state.
  • Unlike open batteries, an AGM battery will never leak. It can, therefore, be placed safely in any position.

Cons

  • Requires the use of a high-quality regulator
  • Does not tolerate high temperature. More exactly, its life is divided by 2 at each temperature increase of 10 ° C. So an AGM battery with a floating life of 6 years at 10 ° C will have only 3 years of service life if the temperature is 20 ° C.

3. GEL batteries

This type of battery is an evolution of the conventional battery. Indeed, it is composed of lead plates and electrolyte formed of a solution of distilled water and sulfuric acid just like any other lead-acid battery. The only difference being that silica is added to the electrolyte so that it forms a thick paste. A GEL battery is essentially a jellified electrolyte lead battery.

The lifespan of GEL batteries much longer when compared to other AGM and lead-acid batteries. More precisely, they are eight times stronger than traditional batteries. This is why GEL batteries are the go-to choice to store solar energy in household setups.

Since their self-discharge is significantly reduced, the risk of a GEL battery falling is also lower than most other battery types, even if the vehicle is not started for months. This advantage is due to the fact that it is made from pure materials and lead-calcium grids. It should be noted, however, that a GEL battery must always be accompanied by a charging controller capable of monitoring and absorbing voltage peaks.

Like with anything else, quality comes at a price. GEL batteries are one of the most expensive batteries on the market.

Pros

  • Optimal life
  • No loss of water
  • Easily supports deep discharges
  • Suitable for all seasons
  • Withstands shock and vibration well
  • No risk of leakage. GEL batteries are therefore perfect for motorcycles and off-road vehicles

Cons

  • Cannot be left completely discharged for more than 6 months
  • Does not support high charging speeds
  • Higher risk of reduced lifespan if not used correctly
  • Doesn’t resist overcharging
  • Significantly higher purchase price

4. EFB batteries

As their name suggests, Enhanced Flooded Batteries are nothing more than a reinforced conventional lead-acid battery. Thanks to specific additives and the use of polyester fiber, the active mass is much more effective. The use of higher-quality lead alloy material promotes better electrical exchanges. EFB batteries have more efficient separators between positive and negative plates but retain a conventional liquid electrolyte.

EFB batteries have a better cycle efficiency and are highly resistant to shocks and jolts. They are mainly used as OEM batteries in vehicles equipped with start-stop systems because of their relatively low cost and resistance to deep-discharges.

EFB batteries are a more cost-effective solution when compared to AGM technology since the design uses a conventional open lead-acid battery with improved specification and performance. While EFBs are usually more affordable than AGMs, they also have a reduced life expectancy and will need to be replaced more frequently.

Pros

  • Supports Start-Stop systems
  • Can be used on vehicles equipped with regenerative braking systems
  • Higher power than conventional batteries
  • Suitable for extreme cold weather
  • Recommended for intensive use

Cons

  • Shorter life expectancy
  • Purchase price higher than a conventional battery

Classification of battery power

For an accurate classification of car batteries, the current (amps) or load capacity is used as the ultimate measurement unit. For the majority of automotive batteries operating on 12 volts electrical systems, the nominal capacity serves as a defining feature and indicates the amount of current that the battery can produce.

Thus, if a battery needs to be charged for 20 hours with five amps to reach a full charge, the nominal capacity of this battery would be five times 20 hours, or 100 amp-hours (Ah).

Auto mechanic refilling the water level in a car battery
Open-type batteries need regular maintenance

How long do car batteries last?

Average lifespan

Depending on the type of battery, the life expectancy can vary a lot. Lead-acid batteries, for example, are very fragile. They are sensitive to overloads, partial loads, deep discharges, fast charging as well as temperatures above 20° C and below 0° C.

Even under optimal operating conditions, not all batteries have the same life expectancy. As a general rule, conventional and EFB batteries last approximately three to six years, whereas AGM and GEL batteries usually last longer.

Factors influencing the life of a battery

Different factors determine the lifespan of a car battery, including:

  • The type of battery (Lead-Acid, EFB, AGM, GEL)
  • Conditions of use such as climate and type of vehicle
  • The efficiency of the vehicle’s charging system

All of these factors can cause premature aging and can be combined due to lack of technical knowledge, poorly designed systems or misuse by the user. When not properly controlled, these factors will have a direct impact on all battery’s normal life expectancy.

Different types of batteries will react differently to various factors. In all cases, batteries will last longer when they are correctly used, charged and stored.

Self-discharge rate

It is important to note that a battery discharges slowly even if it is not being used. This is called self-discharge. The normal self-discharge rate of a battery depends primarily on the type of alloy used to manufacture the plates. For example, the discharge rate is particularly high for lead alloys where it can reach five percent per month on conventional batteries, even when new. The self-discharge rate increases rapidly with temperature and age. A lead-acid battery at the end of its life can sometimes reach a self-discharge rate of up to one percent per day.

AGM and GEL batteries, on the other hand, have a lower self-discharge rate, ranging from one to three percent per month.

Deep discharge

Keeping your battery charged at all times will maximize the life of your battery and prevent premature failure. In discharge, the two polarities sulfate and the electrolyte are consumed. If the discharge is complete, the electrolyte will be only composed of distilled water.

The depth of discharge is the amount of energy that has been discharged from the battery. It is given as a percentage of its capacity. An unloading depth of over 80 percent indicates a deep discharge.

Deeply discharging a car battery will significantly reduce its lifespan, especially for lead-acid batteries. Indeed, when a battery is heavily discharged, harmful phenomena such as sulfation, gel, and stratification of the electrolyte will occur rapidly and will cause irrevocable damages.

If the battery needs to be stored or the vehicle immobilized for a certain time, it is recommended to regularly charge the battery to keep it active and fully charged to maintain a good life expectancy.

Each type of battery lasts for a specific number of approximate life cycles depending on its type and design. When the battery has reached the end of its life, even the best chargers in the world won’t cut it and the battery will have to be replaced.

Characteristics specific to certain types of battery

Certain types of batteries react differently to the outside factors, resulting in various specific properties which can be advantages or disadvantages, depending on the case.

For example, AGM batteries do not support high temperatures. More exactly, an AGM battery’s lifespan is divided by two for every increment of 10°C. Therefore, an AGM battery with an expected lifespan of six years at 10°C, will only last three years at 20°C.

It is therefore very important to be aware of the optimal conditions for the use and maintenance of the type of battery you intend to buy. A better or more expensive battery will only last longer if the manufacturer’s recommendations are closely followed.

Man buying a new car battery

How to choose the right battery for your car

When the time comes to buy a new battery, finding the right one for your vehicle may sometimes be complicated. Some vehicles can run with multiple types of batteries while others just can’t. Additionally, OEM batteries are frequently overpriced. So how can you choose the best battery for your car while also ensuring you get the most bang for your buck?

Before rushing to an auto part store and buy the highest rated battery on the market, carefully consider what you need from a car battery and how much you can reasonably invest.

Here are the top five factors to take into consideration when buying a replacement car battery.

1. Age of the car

As your car gets older, your engine and starter will require more energy to start. A more powerful battery than the original is therefore recommended. In this case, it would be wise to take the measurements of the original battery to make sure you buy a replacement one that fits into the battery tray. Modern battery retainers often limit the size of the batteries that can be used on a specific vehicle.

2. How long do you plan to keep your car?

Are you planning to keep your car for several years? Choosing a battery that retains its power better over time and has a longer life, such as AGM and GEL batteriesmight be a good idea.

If you plan on replacing your vehicle soon, a conventional lead-acid battery should be more than enough and will be much more affordable than other long-life batteries.

3. The climate of the region you live in

Some batteries are more resistant to cold than others. If you live north of the 45th parallel, very cold winters will greatly reduce the life expectancy of your car battery. Fortunately, AGM and GEL batteries withstand very cold temperatures and are perfect for car owners living up north.

On the other hand, AGM and GEL batteries don’t support heat that well. If you live further south, a lead-acid battery should be sufficient but will require regular inspection and maintenance of the electrolyte level due to the increased water evaporation.

4. Battery type conversion

When replacing a battery with a more powerful one, the following instructions should be followed. Some types of batteries simply can’t be interchanged with others.

For example, if your car’s original battery is an AGM battery, it must only be replaced with another AGM battery. If the original battery is an EFB battery, it should at least be replaced by another EFB battery. If a battery with a longer lifespan is needed, AGM batteries might be a good alternative. If the original battery is a conventional lead-acid battery, you can also install an EFB or AGM battery without any problem.

When in doubt, always ask a battery specialist before installing a different battery type than what was originally intended by the car manufacturer to prevent damages to your car’s electrical system and possible bodily harm.

5. Start-Stop system

Start/Stop systems have been developed to significantly reduce the CO2 and fuel consumption of recent vehicles. The basic idea is simply to stop the engine in the phases where it is not needed, such as when your car is idle at a streetlight.

On this type of vehicle, the starter and the battery are solicited upon each restart, sometimes up to three to five times more frequently than on a conventional vehicle. Consequently, cars and trucks equipped with a Start-Stop system will require the use of specific types of batteries.

Conventional lead-acid batteries simply can’t withstand such intensive use. Therefore, the use of EFB or AGM type batteries will be needed.

In terms of compatibility, always remember that an AGM battery can replace an EFB battery but not the other way around. You can always upgrade a battery but downgrading it will significantly reduce its lifespan and could do more harm than good in the end.

Auto mechanic replacin  a car battery

How much does it cost to replace a car battery?

The cost of replacing a car battery can vary depending on the type of battery you plan to buy, where it is purchased, and the labor rate of your repair shop. However, there are certain general rules regarding the different price options available to you.

It can usually be said that:

  • Open type batteries are often more affordable than closed type batteries.
  • Models offered at auto repair centers, car repair shops or car dealerships are often more expensive than batteries sold in supermarkets or online. On the other hand, if you choose the second option, you will need to replace the battery yourself.

The cost of the battery

The typical price of a conventional lead-acid car battery is usually between $100and $250. In the case of an SUV or a van, it is between $150 and $350. In the case of GEL and AGM batteries, the cost can easily exceed $400.

The cost of even bigger and more powerful deep-discharge cylindrical batteries designed to power energy-intensive aftermarket audio systems can easily reach way over $600-$700. Luckily, unless you intend to compete in an audio system competition, you shouldn’t need a battery as expensive as those.

The replacement cost

The total cost of replacing the battery depends on the labor rate of your auto mechanic and the time required to replace it. On most cars, replacing a car battery is fairly easy and shouldn’t take more than 30 minutes. In other cases, you may own a car with a battery located somewhere harder to reach like some Dodge vehicles with the battery located in the front fender or a newer Prius with the battery hidden under the back seat. If it’s your case, the time required to replace your car battery might go up.

Labor rates are also different from repair shop to repair shop and depending on where you live. Car dealers may charge upwards of $75 per hour while smaller repair shops are often more affordable. Labor rates are also frequently higher in bigger cities.

Last words

Buying the best battery possible for your car is never an easy task. With battery manufacturers investing large amounts of money into marketing campaigns and releasing new batteries with always more bells and whistles every year, it’s sometimes hard to separate the facts from the fancy. When trying to find the right battery for you, always refer to your vehicle’s repair manual and look for the manufacturer’s recommendations. When in doubt, make sure to ask for a certified automotive technician’s opinion. A trustworthy mechanic will be able to point out the correct replacement part, explain the different options available to you and recommend a battery that truly fits your needs and your budget. Selecting the best battery alternative will ensure it lasts for as long as possible while ensuring that you get the most bang for your bucks.

About Jean-Claude Landry

Jean-Claude is the editor of TheMechanicDoctor.com and has been a certified auto mechanic for the last 15 years, working for various car dealers and specialized repair shops. He turned towards blogging about cars and EVs in the hope of helping and inspiring the next generation of automotive technicians. He also loves cats, Johnny Cash and Subarus.

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