# What is an ampere-hour and why do you need to know it?

Knowing what ampere hours are, or what is the same, Ah, it is essential to know what the charging capacity of a battery is, as well as other important factors in terms of their performance and operation. Amp hours, or amps per hour, is a unit of electrical charge used to measure the amount of electricity passing through the electrical conductors of a battery based on 1 amp hour. Next, we analyze everything you need to know about this unit of measurement and in what cases it is used, as well as its equivalences in other units of measurement of the electricity load.

## What is an ampere hour?

As we mentioned in the introduction, the ampere hour is a **unit of electrical charge**. This is indicated in many electronic devices, such as common batteries —those used by mobile phones or external batteries—, in **solar panel batteries** and in condensers, among others. This measurement determines the amount of electrical charge from one amp hour. With the ampere hours we can know the **amount of electricity that a battery is capable of storing at the time of charging**as well as the **amount of electricity it can supply when discharging** —that is, by making use of it—. Something that we must take into account, however, is that the times of the amps per hour are not always the same —despite the indications that appear specified by the manufacturers in the product—. And it is that, over time, the performance of the battery is affected. Thus, the rate of discharge of the battery is usually higher so it experiences a higher energy loss and a variation in amp-hour times occurs.

## What is the Ah capacity of a battery?

Typically, amp hours, or **the Ah capacity of a battery, are usually reflected in milliamps per hour** —its abbreviation is indicated in mAh—. Thus, the batteries of the phones usually have a capacity of between 1,500 mAh to 5,000 mAh – in the case of those higher-end phones. Although, in the case of solar batteries —since they greatly exceed the load capacity— the measurement is usually reflected directly in Ah. We can find from batteries that have a capacity of 95 Ah to 525 Ah, approximately. Batteries also often include other measures of charge capacity such as **watts per hour, or Wh**. This unit is expressed in the form of power per hour, since a watt is an international unit of measurement that is produced by the potential difference of 1 volt and an electrical current of 1 amp. The watt is also used to express 1 joule per second (J/s) —although this would give rise to another article, in order to explain it more clearly, so we will not emphasize it so as not to hinder the understanding of the main concept—.

## What is an Ah equal to?

You must bear in mind that this unit of electric charge **It’s not international, just like the time isn’t.**. The Ah charge capacity of a battery is usually used because the nominal voltage of a battery is fixed, although the most common international measurement used for this is the **coulombs**. A coulomb (C) is a unit derived from the international system for the measurement of the physical magnitude of electric charge, or quantity of electricity. This is defined as the amount of charge that is carried in one second by a current of one ampere.

Namely, **1 coulomb equals 1 amp per second**. Now, how do you go from Ah to C? Very easy. To do this, we must take into account that a **1Ah = 3,600C** Or what is the same, **1mAh=3.6C**. Another formula that we can use to **know the accumulated energy** in the batteries is **convert the measure to joules** —international unit of measure to measure energy, work and heat—. In this case, what we need to do is **multiply the intensity of the current that passes through the battery by its tension or voltage**. To do this, we must look at the battery specifications to know the voltage provided by the battery. We can also use an ohmmeter to measure the electrical resistance of the electrical circuit or component and obtain its voltage. Knowing these data, we would have to multiply the Ah by the coulombs and by the voltage. For example, if we have a battery with a capacity of 1.2 Ah and a voltage of 5 V, we would have to multiply them by each other and by 3,600 C. The result would be 1.2 Ah x 3,600 x 5 = 21,000 J.

Read more: Kilowatt-hour (kWh) and Kilowatt (kW)?