What Happens If You Put The Wrong Size Battery In Your Car? - Car, Truck And Vehicle How To Guides - Vehicle Freak (2023)

Some engines are cramped, like the inside of a clown car. Many times, the battery is a tight fit. So much so, that various car manufacturers put the battery in the trunk or wedge it into a small corner.

But when it comes to replacing a battery, what happens if you put the wrong size in your car?It can lead to a whole host of issues from an improper drain on the voltage that could leave you stranded somewhere to physical damage to the car’s body.

Let’s break down the different battery issues:

Possible Battery Issues

Wrong voltage

If you use the wrong voltage battery, trouble could be brewing. The vehicle’s electrical system will not operate properly and there’s a risk to your car’s electronics as well as the battery.

Wrong terminals

The type of battery terminal, its location, and its orientation can vary widely. Some terminals are quite common, some are proprietary to certain models, and some are downright weird. The right fit is all about connectivity.

Wrong size of the battery

If it doesn’t fit the space designed to contain the battery, you may find it difficult to cover the battery, strap it in, or even close the car’s hood. And then there’s the strain of extra vibrations.

Wrong battery capacity

Not enough electrical current (amps) will make it quite difficult to even start the car’s engine. It’s going to get heavier and more expensive to make it do its job properly.

What happens if the battery is too small?

What Happens If You Put The Wrong Size Battery In Your Car? - Car, Truck And Vehicle How To Guides - Vehicle Freak (1)

Usually, when you put a smaller battery in your car, it doesn’t start. If it does, most of the car’s electronics won’t power up, including some of the more vital electrical systems.

With a smaller battery, accessories will cause it to drain rapidly. Just listening to the radio is a demanding task. A lot of starts and stops will tax the smaller battery as well, not allowing for any kind of recharge.

Batteries are rated for their life expectancy, as well as their cold-cranking amps (which defines their ability to start an engine in cold temperatures). Say you’re trying to start a V-8 engine with a battery made for a four-cylinder car, and it’s frosty outside.

An undersized battery just can’t deliver the power to your car’s engine, or the accessories (especially while the car is off).

(Video) How To: Buy the right battery for your car | Cooley On Cars

If you’re out running errands all day, constantly starting and stopping the car, the battery doesn’t get the chance to fully recharge. This, in turn, could cause the alternator to overheat and there’s a risk of long-term damage.

And physically speaking, one major concern with a smaller battery is how it doesn’t seat properly in the compartment it was designed for, and that extra vibration takes a toll on the battery and its cell connectors and separators. Again, the risk for long-term damage.

What happens if the battery is too large?

Similar, long-term effects can happen to your car from using a battery larger than what the manufacturer recommends.

Buying a battery right off the shelf, once home you might find it doesn’t fit your vehicle’s battery compartment. That’s because along with power and cold cranking amp ratings, car batteries also come in a variety of sizes and configurations, such as top-mount versus side-mount.

Along with where the battery sits, one must be acutely aware that manufacturers precisely match their alternators and batteries to the vehicle’s power requirements. A mismatched battery/alternator combination could lead to alternator overheating, and long-term damage.

If the battery is too large, it may not even fit in the battery compartment due to the difference in size, terminals, and mounting configurations.Even if you were able to squeeze it in a spot, and get it strapped in, there’s still the issue of cold cranking amps.

Not enough cold-cranking amps and your car will see issues come winter. And that will shorten the battery’s life.

What Happens If You Put The Wrong Size Battery In Your Car? - Car, Truck And Vehicle How To Guides - Vehicle Freak (2)

What’s the right battery for my car?

Before heading out to buy a new car battery, you should first check the owner’s manual for the battery specifications recommended by your car’s manufacturer.Just to note, not using the original brand of battery that came with the car is just fine as long as it has the same size and output recommended by the manufacturer.

If you don’t have the owner’s manual, you can always check the info on the current battery (if it’s the original) or just hit up the online search engine for the exact specifications of your car.

Some important battery terminology:


On modern cars, a 12-volt battery has become the standard and it’s what you’d most likely find at the local auto parts store. Vintage cars might still use a 6-volt system.

(Video) How to Test and Replace a Bad Car Battery (COMPLETE Ultimate Guide)

There is marine (deep cycle) batteries, which are usually 12 volts and can fit in many cars. They are not known for being compatible with alternators and they won’t be as efficient or long-lasting.


Batteries generally have two amp ratings, cold cranking amps (CCA) and cranking amps (CA). Amps are the amount of actual power your battery can send to your starter.

Cold-cranking amps are the number of amps that a 12-volt battery can produce for 30 seconds at roughly 0°F (-18°C) while maintaining at least 1.2 volts per cell (7.2 volts for a 12-volt battery).

Cranking amps is the number of amps that a 12-volt battery can produce for 30 seconds at 32° F (0°C) while maintaining at least 1.2 volts per cell (7.2 volts for a 12-volt battery).

It’s good to note that you can’t have too many cold-cranking amps. The more CCA, the less the battery will suffer in cold temperatures, and the better it will be at sustained cranking if the car is hard to start or you’re taking a lot of short trips.

Having too few cranking amps, on the other hand, can shorten the lifespan of both your starter and your battery.

What Happens If You Put The Wrong Size Battery In Your Car? - Car, Truck And Vehicle How To Guides - Vehicle Freak (3)

Size Group

Batteries come in different sizes, but on most modern cars, the battery compartment doesn’t have much room to spare, so it’s important to get the right size group. In general, the size group is represented by a number … and that can be a confusing situation to understand. For instance:

  • 75 is smaller than a 24.
  • 26 is also smaller than a 24.
  • 34 is the same size as a 78.
  • 65 is bigger than a 78.
  • 31 is bigger than any of those.

The size group represents the overall dimensions of a battery. If it’s too tall, too wide, or too long to fit in the battery compartment, it will probably be difficult to close the car’s hood or battery cover. Certainly double-check the correct specifications.

If the batter is smaller than the compartment, you will introduce a different set of issues to the car, such as battery vibration. Vibrations can destroy a battery by causing cracks in the cell connectors and separators. One exception would be the AGM style battery, which is designed to resist vibration.

Another thing about size group numbers is that sometimes they have a letter added to them which dictates the position of the terminal on the battery. For instance:

  • 24F will have terminals on the opposite side as 24.
  • 75/78 will have terminals on the side.

Terminal Orientation and Type

There are different terminal orientations and types. One of the most common is a top post. But you will see that a growing number of manufacturers have gone the proprietary route with their battery terminals, which may wrap around or otherwise encase part of the battery.

(Video) How to Test a Car Battery with a Multimeter

This requires very specific placement of the terminals because the placement of the positive and negative terminals doesn’t have an extra centimeter of battery cable. If they’re on the wrong side, you won’t be able to attach the cables.

What Happens If You Put The Wrong Size Battery In Your Car? - Car, Truck And Vehicle How To Guides - Vehicle Freak (4)

Battery Types

AGM (Absorbed Glass Mat)

This type of battery is “spill-proof” if it’s ever exposed. The tight packing of an AGM battery is also the most impact-resistant and boasts the least internal resistance. Usually, premium AGM batteries are maintenance-free with no acid leaks or corrosion on surrounding parts. AGM batteries can do anything that is flooded and GEL batteries can do but are a notch more reliable.

Flooded or “wet cell”

Most cars have a lead-acid battery, usually called a “flooded battery.” They are generally suitable for nearly every car, yet not without issues.

These batteries use lead plates, a sulfuric acid electrolyte, and plate separators. Generally, flooded batteries aren’t sealed, and don’t recombine the gasses to liquids internally. Instead, these gasses are vented externally.

Internal gasses produced are released directly to the environment. Through these same vents can flow acid, steam, and condensation, leading to maintenance.

Flooded batteries do require maintenance, in the form of water, to routinely replenish lost electrolytes through the vents. Lead plates start to deteriorate when they touch the atmosphere, so if you fail to maintain your batteries, they will corrode and fail. Flooded batteries hold very good rates of charge for the price but require more work.

GEL cell

GEL cell batteries are sealed, like an AGM battery. However, care must be taken with GEL batteries not to expose them to high amperage situations. High amperage situations can scar the inside of a GEL battery, creating a pocket. These pockets allow the plates to begin corroding, leading to premature failure.

GEL batteries should not be used for fast charging/discharging, or high amperage charging/discharging situations. GEL Batteries are slightly stronger in regards to internal construction than a flooded battery but do not have the physical strength of an AGM battery.


What Happens If You Put The Wrong Size Battery In Your Car? - Car, Truck And Vehicle How To Guides - Vehicle Freak (5)

There are a growing number of vehicles with “Start-Stop” functionality. This turns off the engine when sitting in traffic and restarts when the foot is let off the brake ready to go. This flexibility does stress a battery and the average flooded batteries won’t hold up. Usually, Start-Stop vehicles contain AGM batteries.

Fully electric

Then there are electric cars, which most likely have lithium-ion batteries. These weigh much less than regular car batteries and are much more efficient. They do tend to have a shorter lifespan than conventional batteries and are far more expensive.

(Video) When Should You Replace Your Vehicle's Battery?

Why is it important to get the right battery?

Modern cars have a plethora of electronics that need the right battery to function properly. As a result, the battery isn’t only for starting the car, it’s quite vital for all the gadgets and accessories.As an example, one of those vital electronics could be your anti-theft system. That’s something for which you want to power on hand all the time.

And you may have other questions:

How does battery size affect safety?

In your modern car, you will have an entire computer system built-in, not counting the computing and electrical power needed for the GPS, audio system, etc. And the battery’s power is needed for:

  • Low tire pressure indicator.
  • Oil change indicator.
  • Cruise control.
  • Anti-theft system.
  • Many safety features.

Using the right battery reduces the risks of having any of your electronics malfunction and leaving you with costly repairs.

How does battery size affect performance?

It’s very important to note that batteries are also responsible for providing power to the electronic fuel injection system and to the alternator, along with a host of other engine parts. When it’s an undersized battery, it could put a lot of extra pressure on those parts, reducing the car’s performance.

In fact, if you have a smaller battery than your car requires, it could refuse to start at all, due to the lack of amps. And even if you can get it to start, most of the electronics are going to be off or barely working. And you will experience faster battery drains.


There are a lot of different options out there when it comes to batteries and it can get really confusing if you’re not familiar. When in doubt, get your battery inspected and/or replaced by a professional. You can drive through an oil changing business like oil can henrys or you can take it to an autobody shop.

Matching the volts, amps, and size of the battery is no easy task. It’s always best to remove doubt and have a professional take care of it. You don’t want to buy a battery that is too large and not have it fit, or have it fit and then cause long term damage that isn’t immediately obvious. Do yourself a favor and get help if you’re not familiar with replacing components like a battery.

Find more car battery-related posts here:

Can A Car Battery Die While Driving?

10 Best Batteries For The Toyota Corolla in 2022

How Many Batteries Does A Chrysler Pacifica Have? Replacement Instructions

(Video) How to Change a Car Battery | DIY Car Repairs | The Home Depot


What happens if you put wrong size battery in car? ›

If you use the wrong size battery, this could cause changes in the flow of electrical currents, resulting in power surges that can damage the onboard computers or other components.

What happens if you put a battery wrong? ›

The cable on the positive terminal uses +12V while the one on the negative side uses -12V. If the positives and negatives are switched, the battery will try to compensate and make the negative 12 volts into a positive charge resulting in a huge surge of power and an enormous amount of heat to be produced.

Can I use a truck battery in my car? ›

Sure, most of the batteries may supply 12v voltage; however, that doesn't mean a big pickup truck is going to be able to use the same battery as a small, zippy coupe. So if you've ever asked yourself, “Are car batteries universal?” the answer is “No.”

Can the wrong battery damage the alternator? ›

Does a Bad Battery Affect Your Starter or Alternator? A bad battery won't usually harm your starter or alternator, however, since both of those components get their voltage directly from the battery, if the battery is underperforming, both the alternator's and starter's performance will be affected as well.

Does it matter what size battery you put in a car? ›

Manufacturers precisely match their batteries to the vehicle's power requirements. An oversized battery could cause your alternator to overheat and wear out sooner. Using an undersized battery in your car could lead to starting problems.

Can I use a more powerful battery in my car? ›

The use of more powerful batteries (in terms of capacity and/or cold starting) has no negative effects on the vehicle concerned.

Can you put a higher amp battery in your car? ›

It might also result in trouble while starting your car. A much higher Ah rating can put a huge amount of load on the alternator, so to get the best replacement car battery, choosing one with the right Ah rating is vital. If the battery is not of the right size, it will not fit properly in the battery tray of your car.

How do you know if you have the wrong battery? ›

Signs you have a bad battery
  1. The car is difficult to start.
  2. Once started, the car doesn't hold a charge for very long.
  3. Dim or flickering taillights and headlights.
  4. Dim interior and dashboard lights.

Can I put a different size battery in my car? ›

Just as with any part or accessory, using the wrong size battery can lead to a host of problems. While it isn't always necessary to use the OEM brand, you should always replace your battery with the size and output that the manufacturer recommends.

What is the difference between a car battery and a truck battery? ›

One difference is the battery voltage. While in cars you may find a 12V battery, in trucks and pick-ups due to their larger engines and greater horsepower, 24V batteries are the norm. This naturally makes truck batteries more expensive compared to car batteries.

What should you not do when changing a car battery? ›

Be careful not to let the wrench touch both the negative and positive terminals simultaneously, as it could create a spark, cause the battery to short out, or even damage the engine's computer or the vehicle's electrical system. With the negative cable set to the side, repeat the process with the positive cable.

What ruins your alternator? ›

Most of the time, alternators fail as a result of age or use. However, some other factors can cause an alternator to fail prematurely. Fluid leaking on the car alternator can commonly lead to failure. Often, engine oil or power steering fluid can work its way into the alternator and cause it to malfunction or fail.

Can a wrong car battery cause electrical problems? ›

Yes, the electrical problems you are experiencing are likely related to your car's battery. Quite often, a bad battery will have enough power to start your engine, but can't support the additional load of other electrical components, like power windows.

How do you tell if the alternator is messed up? ›

7 Signs of a Failing Alternator
  1. Dim or Overly Bright Lights. ...
  2. Dead Battery. ...
  3. Slow or Malfunctioning Accessories. ...
  4. Trouble Starting or Frequent Stalling. ...
  5. Growling or Whining Noises. ...
  6. Smell of Burning Rubber or Wires. ...
  7. Battery Warning Light on Dash.
24 Aug 2020

Can a smaller battery jump a bigger battery? ›

A smaller car can even jump-start a larger one if the jump leads are connected for a few minutes, possibly with the smaller car's engine running. That's because that allows some charge to be transferred to the other car's battery, which can then provide most of the starting current.

What will drain your car battery fast? ›

Electrical devices or lights left running, a defective charging system or alternator, and extreme weather are some common reasons but maybe it's just time to get a new battery.”

What happens if you put a bigger battery? ›

When you use a larger battery, your car's electrical systems don't automatically start pulling more current simply because it's available. The current draw will remain the same. Because of this, a larger battery will not deplete faster than it's smaller counterpart.

Is it OK to have more cold cranking amps? ›

Well, that's still very important, because cold, cranking amps tells you the ability of the battery to do work right now. And the higher the cold cranking amp rating of the battery, the better it is for your car.

How many amp should a car battery be? ›

An average car battery has a capacity of around 48 amp hours which means that, fully charged, it delivers 1 amp for 48 hours, 2 amps for 24 hours, 8 amps for 6 hours and so on.

Can too many amps damage a battery? ›

Yes, it does! Each and every battery types are made up of special chemicals and they charges and discharges in a given time period. Every one of them has their own current rating at which they can be charged and above which if you go it will harm the battery!

What does a clicking sound mean when your car won't start? ›

It might be a battery or alternator problem.

Perhaps your battery's dead, or your alternator, which charges the battery, isn't working correctly. If the source of the clicking is electrical, the starter (a small motor energized by the battery that gets the engine running) doesn't have enough juice to stay powered.

When I try to start my car it just clicks rapidly? ›

Car Makes a Series Of Rapid Clicks

This lack of electrical current could be because of a failing battery, a bad connection at the battery or even a bad alternator that isn't properly recharging your battery. Best case scenario, your battery or posts need cleaning.

When your car won't start but all the lights come on? ›

If your headlights can turn on, but your car won't crank, that means that your battery is charged, but either the starter or ignition is the problem. If the starter or ignition is the problem, a starter engine can be jumped by using a charged battery.

Are truck batteries bigger than car batteries? ›

For larger cars, pickup trucks and SUVs, the physical size of the battery might be larger than the car battery that would fit into the battery tray of a small coupe. The standard regarding battery sizes is in place to help prevent any confusion and make sure you can install your battery without difficulty.

What are the 3 different types of car batteries? ›

AGM, EFB, Lead Acid: Three different battery types – many common features. AGM and EFB batteries are characterized by their high performance.

What happens if you put the wrong battery in a truck? ›

Selecting the wrong battery may also cause the start-stop system to fail. As a result, the engine is rarely or never switched off when the vehicle is at a standstill (e.g. at a traffic light). An incorrect battery can cause a number of various functional failures.

Does car need to be reset after changing battery? ›

A: After a battery is replaced in some vehicles, the battery charging system monitoring system will need to be reset. This can be performed with a scan tool or dedicated battery reset tool.

Do I need to program my car after changing the battery? ›

Under normal circumstances, you don't need to do anything else other than keep driving the car after resetting the computer. The ECU will eventually relearn its ideal settings and reprogram itself with use.

Which terminal should be removed first on a car battery? ›

When disconnecting the cables from the old battery, disconnect the negative first, then the positive. Connect the new battery in the reverse order, positive then negative.” When you are replacing your car battery, It isn't always easy to remember the order in which to disconnect and reconnect the terminals.

Can a small car jump a truck battery? ›

Great question! A car can jump-start a truck without issue if the jumper cables are connected properly. To jump-start your friend's truck—or really any vehicle, even a semi-truck—with your car, follow these instructions: Position your car so the hood is in front of the other vehicle's hood.

Are all truck batteries 12v? ›

When selecting a new battery, you need to be sure that the replacement matches the voltage requirements of your vehicle. Most commercial trucks require a single 12 volt battery. Diesel engines require more power to start their engines and may need two batteries connected in parallel.

Can you use a calcium battery in a car? ›

Many modern vehicles use calcium batteries as they are less likely to be affected by extreme weather conditions and higher charge rates. Calcium has been added by the manufacturer for many years.

Can you use a marine battery in a car or truck? ›

Is It Okay to Put a Marine Battery in a Car? Marine batteries, or boat batteries, are built specifically for the harsh environments that boats are traveling through. That being said, technically, yes they can be used to power your car or truck. However, marine batteries are not always designed for cranking only.

Can you damage a car battery by jump starting? ›

So what about your car when jump-starting another battery? This process will put slight stress on your battery and alternator. However, in most cases, this process is harmless. A healthy battery will be unfazed by the jump-start, and your battery will recharge as you drive.

Can you damage your car by giving a jump-start? ›

Like most electronics, a power surge can cause damage to the electronic systems of a modern car. A seemingly well-meaning jumpstart can cause said power surge and impact the effectiveness of onboard computers, safety systems, damage the engine and be the result of expensive repairs.

Does jumping a car hurt your alternator? ›

Impact on alternators from jump starts: The alternator's design makes it fairly impervious to negative effects from jump starting. However, the alternator can sustain instant damage if the polarity of the clamp connections is mistakenly reversed.

What type of battery do most cars and trucks use? ›

Flooded Batteries

Standard flooded lead acid batteries are the most common batteries found in cars and trucks. They are cheaper than AGM batteries, making them the preferred choice for a large percentage of drivers. The interior of 12-volt lead acid battery is divided into six different cells.

How many amps does a truck battery need to start? ›

400 to 600 amps will be more than enough to jump-start any normal, consumer vehicle. Commercial vehicles may require up to 1500 or 2000 amps. Compact and small vehicles can be boosted with as little as 150 amps.

What battery fits in my truck? ›

You can look at the battery section of the Owner's Manual of the car or truck. If the owner's manual can't be found, look at your existing battery and see what BCI Group Size is already installed. The Group Size is labeled in several places on the battery. Generally on the top and/or on the front of the battery.

What kills battery in a car? ›

Electrical devices or lights left running, a defective charging system or alternator, and extreme weather are some common reasons but maybe it's just time to get a new battery.”

What does putting an aspirin in a car battery do? ›

The acetylsalicylic acid from the aspirin will combine with the battery acid and increase the charge in the battery, and the water will help restore the electrolyte in the battery.

What drains a car battery not in use? ›

A slow battery drain when everything is off is called a parasitic power loss. This happens when something – a glovebox light, an amplifier, any electrical component – is pulling power from the battery when it shouldn't.

What happens when you use a marine battery in a car? ›

Marine batteries are probably not recommended to power cars for a long period of time. This is because they would probably shorten the battery's lifespan. In fact, they may even lessen the lifespan of your car's electrical parts.

What is the difference between a car battery and a marine battery? ›

Marine batteries feature thicker internal lead plates than car batteries. This allows them to discharge energy over a longer period of time. Housings are also typically larger than an equivalent car battery, with extra plastic protection since boating environments are not nearly as smooth as on-road driving.

What type of batteries are typically used in a car or truck? ›

Are either one the same type of battery as the one in your car? Probably not, at least for now. The vast majority (nearly all) car batteries are some form of lead-acid battery.


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