Can You Put a Different Size Battery In Your Car?


Updated: Jul 1, 2021

Modern cars nowadays have very tight size requirements regarding what vital components can be used. So what will happen if you put a different size battery in your car? Just like with any component or accessory, putting a different size battery can lead to a variety of issues on your car, but it depends on what you mean by “different size”

Different Battery Voltage
If you use the wrong voltage battery, big problems could arise. The vehicle’s electrical system (99% 12 volts) will not operate properly and will damage your car’s electronics and the battery. Although the chances of you buying a different voltage battery are very low.
Different Terminals
The terminal location/type/orientation on your car battery can vary. Some are common, some are proprietary, etc. It is important to get the right one, as the battery might not even fit, and even if it can, the cables won’t be long enough to connect it, or won’t attach at all
Different Battery Size
It won’t fit the space designed to contain the battery. Even if it can fit, it’s gonna be very problematic or near impossible to close the hood or battery strap. 
Different Battery Capacity
Not enough current (in Amperes) will cause you to have difficulty starting the engine. Getting more capacity will likely be a heavier expensive but will usually work fine.

Not using the original battery brand, on the other hand, is completely fine as long as it has the same size and output recommended by the manufacturer. 

What Happens if The Battery is Too Small

In most scenarios, if your battery is too small the car won’t even start. And even if it can start, expect most of your electronics to be off due to a lack of power, this can include your anti-theft system.

  • If your electronics can turn on, having your car accessories on for a long time could potentially cause your battery to go dead really fast, even a simple task as listening to music or radio can be extremely demanding.
  • If you take a lot of short trips on a small battery expect it to perform even worse than it already is. Taking short trips prevents the battery from getting a chance to fully recharge because the most taxing use of a car battery is at its initial engine start. So when you take a lot of short trips the battery simply does not have enough time to fully recharge which will worsen battery life and its ability to keep a charge.
  • If your battery is smaller than the battery compartment, then chances are. It’s not secured properly and will vibrate the battery. Vibration kills the battery by causing cracks in the cell connectors and separators. Although if you have an AGM battery, this shouldn’t be much of an issue as they are designed to resist vibration, are maintenance-free, and non-spillable. Hence the name AGM (Absorbent Glass Mat)

Another thing to worry about is winter and its cold temperatures. Each battery comes rated with its life expectancy as well as their CCAs (cold-cranking cramps) CCA is the rating used to define a battery’s ability to start an engine in cold temperatures

  • If you bought a small battery in the hopes of saving a few bucks, chances are, the small battery you have bought will have a worse CCA rating than your original car battery. So as you can imagine, A bigger battery with a higher capacity with better CCA rating will suffer less in winter conditions, as opposed to the small battery you have bought to cheap out. But this should not be much of an issue if you don’t experience a cold climate often.

If you happen to buy a battery only to realize it is too small for your car, return it. Next time you buy a car battery, make sure to check the owner’s manual on what kind of battery your car needs, and then make a purchase. This will save YOU and your BATTERY from headache

Related: Can You Jumpstart a Car In The Rain?

What Happens if The Battery is Too Large

If your battery is too large, it won’t even fit in your car’s battery compartment because of the difference in size, terminals, and possibly mounting configurations.

  • If you could get it to fit and your hood or battery strap can close properly, nothing bad will happen to your car. But keep in mind that, if it can’t fit in the battery compartment, DIY’ing your way through is not a very good idea.

Coming back to the topic of CCA’s.

  • If the cold-cranking amps are less than the original battery, your car could have problems starting in winter. And the battery will not last as long.

If you don’t want to deal with any of that, but happen to have bought a car battery that’s too big for your car, give yourself a favor, return it and buy a proper one, check if its output, type, and size matches your manufacturer’s recommendations while you’re there.

Related: How To Tell If a Car Battery Is Bad

What Battery Should I Get For My Car?

As we stated earlier, before going out and buying a new car battery you should first consult the owner’s manual to get the specifications recommended by your car manufacturer.

If you don’t have one you can always check your current battery (if original) or google online. It’s better to play safe with batteries for the reasons we listed earlier unless you are skilled enough to figure it out yourself. If you’re not one of those, just get the battery that fits OEM specs for your specific vehicle and engine.

But it is still important to know what each battery term means, and understand it:

1. Voltage

If you own a modern car, it most certainly has a 12-volt battery. it has become the standard for most modern cars and is the battery you would find often at your local auto parts store. Although if you have a much older car it might still use the 6-volt system. There are also 12-volt golf cart batteries, which are usually very large and heavy.

Even though a golf cart battery is able to start a car, most of them aren’t made for cars in mind, and won’t last very long doing so. You would also need to figure out how to place that monstrosity in your battery compartment, which is something we just can’t recommend unless absolutely necessary.

There is also marine (deep cycle) batteries which are usually 12 volts and can fit in many cars. but it won’t play nicely with your alternator, and even if it will, it’s not going to be efficient and won’t last very long. 

2. Amperage

Starting Batteries are often used as daily drivers. They deliver one large burst of power to start a normal engine. They 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.

(CCA) is the amount 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). (CA) is the amount 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). 

In other words, CCA/cold-cranking amps determine how much power you need to start your engine. There is no such thing as too much CCA.

So the more cold cranking amps your battery has, the less it will suffer in cold temperatures and the better it will be at sustained cranking if the car is hard to start, or frequent cranking if you take a lot of short trips.

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

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 is important to get the right size group. The size group is represented by a number which is really confusing to understand

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

The truth is, size group does not actually represent how “big” or “small” a battery is, but rather the dimension of a battery. If it is too tall, wide, or long it will not fit in the battery compartment, and even if it will, it will be pretty much impossible to close the hood or the battery cover.

But if it is smaller than the battery compartment it will introduce other issues, such as battery vibration. Vibration can kill a battery, causing cracks in the cell connectors and separators.

Although if you have an AGM battery, this shouldn’t be much of an issue as they are designed to resist vibration. Another thing about size group numbers is that sometimes they have a letter added on to them which dictates the position of the terminal on the battery. For example:

24FWill have terminals on the opposite side as 24
75/78Will have terminals on the side

4. Terminal Orientation and Type

There are different terminal orientations and types. One of the most common ones is called a top-post. Although an increasing number of cars have gone proprietary with their battery terminals which wrap around or otherwise encase part of the battery.

This requires a very specific placement of the terminals because the placement of the positive and negative terminals don’t have an extra centimeter of battery cable, so if they are on the wrong sides, you won’t be able to attach the cables.

There are many reasons why it can be propitiatory, but we will not discuss this here. One positive takeaway is that it’s going to be very difficult to put terminals on the wrong posts so that even your grandma could do it! Assuming you’re using the correct battery in the first place. But what about adapters? Well, adapters could work, but it’s not a guarantee  

5. Battery Type

Most cars have a lead-acid battery, which is generally referred to as a “flooded battery” Those batteries are suitable for nearly every car, but not without issues. To better understand the different battery types, here’s a chart.

AGM (Absorbed Glass Mat)
AGM Batteries are “spill-proof” if it is ever exposed. The tight packing of an AGM battery is also the most impact-resistant and boasts the least internal resistance. Premium AGM batteries are maintenance-free. No acid leaks, no mess while charging, no corrosion on surrounding parts. AGM batteries can do anything that flooded and GEL batteries can do, just better.
Flooded or “wet cell”
AGM Batteries are “spill-proof” if it is ever exposed. The tight packing of an AGM battery is also the most impact-resistant and boasts the least internal resistance. Premium AGM batteries are maintenance-free. No acid leaks, no mess while charging, no corrosion on surrounding parts. AGM batteries can do anything that flooded and GEL batteries can do, just better.
GEL cell
GEL cell batteries are also sealed just like the AGM battery. But that’s where the similarities end. Great care must be taken with GEL batteries not to expose them to high amperage situations. High amperage situations can literally ‘SCAR’ the jelly 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. Use the other types listed for these high amperage situations. GEL Batteries are slightly stronger in regards to internal construction than a flooded battery but pale in comparison to the physical strength of an AGM battery.

Some newer cars have a thing called “Start-Stop”. It turns off your engine when you’re sitting at a traffic light and restarts when you take your foot off the brake to go. That can stress a battery really hard and your average flooded batteries won’t hold up well. So instead, those cars usually have an AGM battery.

Hot rodders would often want Gel Cell batteries. Both Gel Cell and AGM batteries come in the same size groups as regular flooded batteries.

There is also a saying that some older alternators may not work well with AGM batteries, but we are unsure about that.

If you have an electric car or use an RV you will most likely have a lithium-ion battery. They are much lighter than regular car batteries and are more efficient. They also tend to have a somewhat shorter service life than a conventional battery and are pretty expensive.

Why Is it Important to Get The Right Battery?

Modern cars nowadays have a lot of electronics that need the right battery to function properly. As a result, the battery isn’t only for starting the car now as it serves a vital purpose for electronics.

One of those electronics could be your anti-theft system. As you can imagine, it’s not a nice scenario when someone breaks into your car only because your battery didn’t function properly or wasn’t the right one. If this wasn’t enough to convince you, here are other reasons.

1. Safety

As we stated earlier, if you have a modern car, you will have a lot of electronics that make your car function. Some cars even come as far as having an entire computer system built into them, that is not just for GPS, audio, etc. But instead control important things such as:

  • Low Tire Pressure Indicator
  • Oil Change Indicator
  • Cruise Control
  • Anti-theft System
  • Many Safety Features
  • Etc,.

Using the right battery reduces the risks of having any of your electronics malfunction and leaving you with costly repairs. Although it is definitely possible to get a battery that is a different spec than your original, but only if you know what you’re doing. But if you picked wrong, it could have consequences that we listed at the top of the article.

2. Performance

Batteries are also responsible for providing power to the electronic fuel injection/alternator as well as other parts. When the battery isn’t right it puts a lot of extra pressure on those parts, reducing performance.

In fact, if you have picked a smaller battery than you were supposed to, your car could refuse to start at all, because there just isn’t enough amps available. But even if it can start, most of your electronics are going to be either off, or partially working. You could also experience faster battery drains.


We hope we explained the effects of putting a different sized battery in your car, and hope you were able to make up your mind regarding it. If you have anything to add, feel free to leave a comment down below.

2 thoughts on “Can You Put a Different Size Battery In Your Car?”

  1. I have a 2008 Ford Taurus SEL. It calls for a group 58 or 59 battery. We put a Group 26 battery in it as we were in a remote area and that is what they had to sell us. It was smaller size-wise but we secured it properly. Car had destroyed the old battery but it was 4 years old and no longer holding a charge. The CCA on the group 58 was 550CCA. The CCA on the New group 26 was 540CCA. Both 12 VOLT Etc. Aside from the slight difference in size and CCA, is it OK to leave it in the car and not replace it? I was told by (someone trying to tell me I needed a new alternator) that the battery would damage the alternator. How? The voltages are the CCA’s are close enough. I know I am missing something. Why is one heavier than the other etc.? Anyway, the battery has performed fine. Just wondering if I am missing something. THNAK YOU!!

    • I’ve never heard that a bigger/smaller car battery has ever damaged an alternator. Car batteries are all the same voltage, except for really old cars. The only difference is capacity and throughput, so if your car seems to be running just fine with a smaller battery without any anomalies, and it does not vibrate or shake inside the compartment, it is probably fine. But, is is better to play on the safe side if uncertain.

Leave a Comment