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What Happens If I Use the Wrong Group Size Battery?

Power - by Joe Weber - updated on 3/8/2023

Woman in an orange top on the phone looking under the hood of a vehicle

Cars, trucks and batteries come in all shapes and sizes from the tiny subcompact smart car to the massive Ford F-350 Super Duty and everything in between. Every car or truck on the road has a pre-designated battery group size that the car must use in order to function properly. You might be asking yourself, can I use a different group size battery? While this is possible in many situations, it is not a recommended practice.

Misuse can be broken down into two groups, using a battery too big and using a battery too small. Read below to learn why using a different size battery other than what is recommended is such a bad idea.

Using A Battery That is Too Large

  • Will physically not fit in the battery compartment without modification. The battery compartment and holders in your vehicle are designed for a specific battery size, nothing more, nothing less. Attempting to use a larger battery and either forcing it into place or using alternative means to hold it in place can potentially cause structural damage to the battery or the car.
  • Will produce too high of voltage. By installing a larger battery, you may inadvertently install a battery of higher voltage than is required. This could cause undercharging and even burning out the electrical system in the car. Burning out the car's computer is very expensive and the fix can cost thousands of dollars.

This typically doesn't apply with modern cars that use the standard 12V battery system. In some vintage cars, it's important to use the correct voltage battery as some vintage models used 6V batteries.

Using A Battery That is Too Small

Attempting to use a smaller battery than what the car is designed to accept can cause the following problems.

  • Lower Voltage
    Some vintage automobiles take 6V batteries but 12V is the standard battery voltage for all modern vehicles. Installing a lower voltage battery, say a battery less than 12V in a modern car, will result in overcharging damage and significantly lower performance of your car's electronics. This can cause permanent damage to your electrical system.
  • Low Amperage
    Battery amperage measures the flow of electric current through a conductor. All car batteries have two ratings for amps: Cranking Amps (CA) and Cold Cranking Amps (CCA). Every vehicle has a minimum CCA requirement, and if you install a battery that is below that level, the vehicle may have a hard time starting or not start at all. The higher amp-hours (AH) a battery has, the greater its capacity. Even if it does start, it may not have enough capacity to power your vehicle's electronics well. For instance, your air conditioning may only work on the lowest blower setting or the headlights will be very dim.
  • Starter/Alternator Strain
    Installing an undersized and underpowered battery in your vehicle can be putting extra strain on your starter, especially if you are prone to taking shorter drives. Taking a lot of short trips with a smaller battery installed will eventually lead to you needing to jump start your battery often. This is also very problematic for vehicles equipped with stop-start technology. If the battery is not recharging properly when driving, your car or truck may not start after it shuts off at a red light.
  • Damage to the Vehicle
    Vehicles are engineered with a specific size battery in mind. Installing a physically smaller battery in your vehicle will not be able to be secured with the battery hold down equipment that comes with the car. Not being able to secure the battery will cause the battery to move around and could potentially damage the vehicle and also potentially cause battery acid to leak causing significant safety risks.

Can I Use A Car Battery With A Higher CCA Rating?

As you will see shortly, the same group size battery can come in a variety of CCA ratings so you can choose a more powerful battery for your vehicle if needed. Using a battery with a higher CCA rating than what is recommended by the manufacturer is completely safe and won't harm your vehicle.

If your vehicle has a minimum rating of 630 Cold Cranking Amps and you install a battery with 750, this just means that the extra amperage is there if it's needed, not that it's going to push all of that power out to the starter at once. This is helpful for vehicles with additional power demands, like remote start, etc.

Always Use the Group Size Recommended by the Manufacturer

With all of the above possible consequences, it is extremely important to use the correct size battery in your vehicle. The appeal of higher voltage or capacity or the reduction in weight for your project car won't actually do any good if the battery is not a fit and will more than likely do more damage than it does good.

Here at Batteries Plus, we use our extensive database to easily look up your vehicle and find the correct BCI Group Size that is required for your car or truck.

How Do I Find the Correct Group Size Battery Myself?

There are several great ways to determine what battery fits in your car.

  • If you have your vehicle's owner's manual you can look at the battery section and it will tell you which size battery to use.
  • If you no longer have the owner's manual or can't find it, pop the hood and take a look at the battery currently installed. The Group Size is labeled in several places on the battery. Generally on the top and/or on the front of the battery.
  • There are many reference tools on the internet that you can use to look up the group size that is required.
  • Batteries Plus offers a great fitment finder tool on Select the year, make, model and trim of the car or truck or enter the license plate or vin number and we will show you all of the battery options that are for your vehicle.

Can I Use A Different Type of Battery if the Size is the Same?

It really depends on the car. Some newer cars and trucks that come with stop-start technology and a lot of electronic power demands require the use of an Absorbed Glass Mat battery.

Other cars and trucks can use any of the battery types available for your vehicle. It is important to look at what is recommended on because we will never recommend anything other than what the manufacturer recommends.

What Kinds of Batteries Are There?

There are three main types of lead acid car batteries available to purchase, each with their own benefits.


  • Arguably the most common type of battery seen on the road.
  • Features lower CCAs than other batteries.
  • More vulnerable to extreme heat or cold.
  • Not the best battery for cars and trucks with a lot of electronic accessories (heated seats, remote start, power liftgate, etc.).
  • Most are maintenance free but some may require routine inspection and topping off the liquid electrolyte with distilled water.
  • Generally, come with shorter warranty periods.

Absorbed Glass Mat (AGM)

  • AGM batteries are designed to perform well in extreme hot or cold conditions.
  • Has higher Cold Cranking Amps than flooded batteries.
  • Ideal for vehicles with a lot of electronic accessories.
  • AGM batteries contain a special fiberglass mat separator that absorbs the electrolyte solution making them 100% maintenance-free during the life of the battery and require NO watering.
  • Will generally come with longer battery life and warranty periods.
  • Cannot downgrade to a flooded battery if your vehicle came with an AGM battery.

Thin Plate Pure Lead (TPPL) AGM

  • The perfect battery for the show car, the workhorse or battery that powers even the biggest adventures.
  • Will feature the highest Cold Cranking Amps available.
  • Features the best performance in extreme climates.
  • Built using 99.9% pure lead providing the fastest charge and best run times.
  • TPPL batteries last on average 3x longer than flooded batteries

Need help choosing? In "How to Choose a Car Battery: A Beginner's Guide" we will help walk you through the process of picking out the best battery for your car or truck so you can walk out the store knowing you made a good choice.

Expert Tips

If you are looking to upgrade your current car or truck battery with the longest-lasting, best-performing battery on the market, the exclusive X2Power AGM line will have you on the road for years to come. These batteries are only available at Batteries Plus and have been designed and engineered by car enthusiasts for car enthusiasts.

Never, ever, downgrade from an AGM battery to a flooded battery if your vehicle came with an AGM battery. It could cause some serious problems for you in the long run. If your vehicle came with a flooded battery, you can absolutely upgrade to the stronger, superior performance of an AGM battery.

Automotive Battery Solutions Available at Batteries Plus

As we've learned, it's important to use the correct battery for your car or truck. Choosing the incorrect size can be harmful to the life of the battery and even be damaging to your vehicle. At Batteries Plus, we make it easy for you to find the right battery at the right price and we'll even install it for you so you can get back on the road. Stop by one of our stores around the country to have our trusted battery experts point you in the right direction.

In a hurry? Learn more about scheduling your battery installation online and select an available time that works for you in "Does Batteries Plus Replace Car Batteries?"

More of a DIYer? Take a look at our handy guide, "How to Change a Car Battery" to learn how to safely disconnect your car battery and install a new one.

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