How Many Amp Hours in a Car Battery: Calculating and Conversion

Nov 19, 2020   Pageview:108

Every car owner knows how pivotal car battery is for the car. After all, the car battery is what makes the car up and running. Since the car battery is what makes the car alive, it is important for us to know everything about it, from taking care of the battery to know the amp hours of it. For those who are wondering, we will tell you how to calculate and convert how many amp hours in a car battery.

How do you calculate amp hours on a battery?

A car battery is a common part of every car’s engine. A car battery is one of the main reasons why a car is able to start. It is the place where chemical reactions take places, converting the DC to AC, the current needed for the car.  Besides the chemical reaction inside the battery, there are some terms of the battery such as voltage, amp hours, and many more. Here, we will talk about amp hours.

Amp hours, or AH, is the rating used by batteries to tell the battery owners the amount of current it can give in a certain amount of hour. It is never a bad idea to know the amp hours of a battery. If you know the amp hours, you can predict how long the battery will last until the next recharge.

Calculating amp hours is not hard to do, but it will require some mathematics and patience.

The first thing you should do is to calculate the battery’s current by using a resistor. First, connect the battery to the resistor and look at the display of the current. The display should show around 12 amps. If not, write down the current displayed.

After that, write down the displayed voltage every two hours. You’ll notice that the voltage will go to 0.1 every two hours or so. Once the volts have gone to 12, write down the amount of time necessary to do so. The hours where the volts have gone down is important!

Time to finally calculate the amp hours of the battery! You can calculate it by multiplying the current displayed at the beginning with the time needed for the voltage to go down. Then, multiply the numbers with two. And there you have it, you have your amp hours!

For example, the battery is 12 amps. Then,  it takes 9 hours to 12 amps, then multiplies 12 by 9. Then, multiply the result (which is 108) by 2. The total will be 216, and that’s the amps hours (AH) of the battery!

The process will take hours, but you will get the exact number of AH if you use this process.

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How many amp hours in a car battery?

The amount of amp hours in a car battery depends on the battery. However, amps, or amperes, is necessary for the battery. After all, the ampere is needed for the delivery and circulation within the battery. Ampere is the main thing that causes the chemical-electrical process to happen. If the battery does not have enough ampere, it will cause a discharge. The discharge will result in corrosion.

Moreover, there are many things that can affect a battery’s amp hours. Some of those things are the battery’s age, weather, and many more.

As it can be seen, the ampere does play a big role when it comes to car battery. For this reason, it is recommended to get a car battery with high amp hours, as it is extremely important for the battery,

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How do you convert CCA to AH/Amp Hours?

Some of us might not realize that it takes extra power for cars to start up the engine when it’s cold. Such occasion is what we call as CCA or Cold Cranking Ampere. CCA is the rating that shows the car’s ability to start up in a cold-weather while maintaining half of the battery’s volt. The higher the rating is, the higher the car’s ability to start its machine in cold weathers. So if you live in a cold region, you will need to take extra precautions when it comes to the CCA.

However, there are times when some of us prefer to measure in form of AH or amp hours. If you want to do that, you will have to convert CCA to AH/amp hours.

Unfortunately, CCA and amp hours are not related to each other, so you will have no other choice but to guess according to the rule of the thumb. The rule of the thumb for converting CCA to amp hours is divide the CCA by 7.25. For example, if your battery has 1500 CCA, you need to divide it by 7.25 to get the predicted amp hours. In this case, the AH is 206. Usually, such AH can help the battery last for 20 hours.

Although there is no fixed rule when it comes to CCA and amp hours, there is no harm in converting one to each other (and vice versa). After all, you can purchase the necessary car battery you need based on the predicted measurement.


From here, we can see the complexity of amp hours and CCA. amp hours are needed because they are the ones who contribute to the process and exchange that happened inside the battery. Without it, the car will not start at all. Hence, it is an obligation of every car owner to know everything about the car battery, including the amp hours and CCA.

Amp hours can help car owners to measure how long the battery would last, while CCA can help them to know whether the battery has the capability to run under cold weather. Although they are not related, car owners can convert each other so that they can purchase the proper battery for their cars. So never consider amp hours and CCA as unimportant, as they can help you tremendously when it comes to buying car batteries!

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