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.

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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


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 IndicatorOil Change IndicatorCruise ControlAnti-theft SystemMany Safety FeaturesEtc,.

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.

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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.