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What Is Ah in Battery


What is ah?

How to calculate ah?

How to calculate the battery life?


When you get a battery, some numbers and symbols are marked ah. But what does ah mean? Here we will discuss and tell you what they mean to help you understand them to make a better choice of batteries.

What is an Ah?

Ampere-hour(Ah) describes the amount of electricity allowed to flow through a battery for one hour at one ampere.


Unlike amperage, AH is a unit of measurement for the capacity of a storage device (such as a rechargeable or deep cycle battery) and is a representation of the power of a battery and is an important indicator of battery performance. Theoretically, we could draw 2 amps continuously for 60 minutes before the 2 amp-hour battery is depleted. Of course, this is under ideal conditions, i.e. at the perfect temperature and stable power.


For batteries with the same voltage, the larger the amperage, the larger the capacity; for batteries with the same amperage, the higher the voltage, the larger the capacity. Usually, the voltage and ampere-hour number together indicate the battery’s capacity, such as 7.4V/10AH, 7.4V/12AH, 7.4V/24AH, and 7.4V/30AH.


What is mAh?


Mathematically there is a formula to calculate ah.

Ampere-hours (Ah) = Current (I) x Discharge time (T)

Let’s look at an example.

A battery with an output current of 10 amperes (A) is discharged in 30 minutes.

Current = 10 A

Discharge time = 30 minutes (0.5 hours)

Ampere-hour = 10 x 0.5 or 5 Ah 1 hour


Take a look at another example below.

Current = 20 A

Discharge time = 3 hours

Ampere-hours = 20 x 3 or 60 Ah for 3 hours


Now you see, if a rechargeable Li-ion battery A has a rated capacity of 2,200 mAh, it can discharge 2,200 mA (3.2 A) in one hour. B batteries are rated at 11000mah, or 10Ah, which means they can discharge 11000 mAh (10.1A) in one hour.


How to calculate the battery life?


An example:

A 12V 4Ah battery is used to power a device with a current draw of 0.5 amps. Let’s see how long the battery will last.


Again, the formula is the same, Ampere-hour (Ah) = Current (I) x Discharge time (T)

4Ah = (0.5 Amps) x T

T = 4Ah / 0.5 A

T = 8 hours

Therefore, the battery can power your system for up to 8 hours.


To give another example of a 7.4V 12Ah battery being installed and used in a 1 amp device.

Ampere-hours (Ah) = Current (I) x Discharge time (T)

12Ah = (1 Amp) x T

T = 12Ah / 1 A

T = 12 hours

Therefore, the battery can power your system for up to 12 hours.

Got it now? This is a relatively simple way for you to make your own predictions about how long the battery will last. Please note that this is only a prediction and actual usage may be different.


Besides, the discharge rate have effect on battery capacity.

Battery capacity decreases with the increase of discharge rate, that is to say, the higher the discharge current, the smaller the capacity of the battery is calculated.


So, if two batteries have the same number of amp hours, do they provide the same amount of energy? Let’s take an example where battery A has a voltage of 14.8V and battery B has a voltage of 18.5V.


Let’s calculate their watt hours

14.8V x 2.2Ah = 32.56Wh – A battery.

18.5V x 2.2Ah = 40.7Wh – Battery B.


Obviously, battery B provides more energy.


Voltage is usually an important parameter of a battery, and when we determine the voltage, then the capacity can be determined by the ampere-hour rating. A larger watt-hour battery will provide more energy than a smaller watt-hour battery.

Another common term we can use is C-Rating. a C rating is a way to indicate how much current a battery can safely deliver.

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