What is a AH in Battery? & What is Watt Hour?

Batteries are used extensively in a variety of applications, including your phone, emergency light, and automotive. When it comes to judging battery life, one of the most useful tools we can use is the battery’s amp hour rating. However, amp hours can provide information about a battery’s capacity, they don’t always work as you might expect. The calculations that go into battery construction are more complicated than the ordinary person wishes to know, as they are with most things.

Fortunately, we’ve put together a quick and simple guide to explain what amp hours are and how to read them while shopping for batteries. This article will explain how to determine the Ah rating of a battery. What is the importance of this? And also what is a Watt Hour?


The amount of energy charge in a battery that allows one ampere of current to flow for one hour is called an ampere hour (abbreviated Ah or amp hour).

In small batteries such as those used in personal vaporizers, or standard AA sized batteries, the amp hour rating is usually given in milli-amp hours, or (mAh).  The rating for large batteries is denoted as Ah. The Ah rating of most deep cycle batteries can be found at several C grades. The C rating indicates how many amp hours the battery can deliver over a given time period.

We may determine a battery’s amp hour rating by multiplying the current by the discharge time, or we can determine how long the battery will last while producing a specific level of current.

A 12V 8Ah Battery, for example, is utilised to power a system with a current draw of 0.5 Amperes. How long do you think the battery will last?

Using the same formula as in the previous example, we obtain:

Amp Hour (Ah) = Current (I) x Discharge Time (T)

8Ah = (0.5 Amperes) x T

T = 8Ah / 0.5 A

T = 16 Hours

As a result, this battery will keep your PC running for up to 16 hours. This is the most straightforward method for estimating how long your battery will last.

The batteries will deliver the amount of current required by the load. The quantity of current a load consumes is totally determined by the load. It gives you a rough idea of how long the battery will last.The capacity of a battery is influenced by the discharge current; as the discharge current increases, the capacity of the battery decreases.

Here are some discharge curves to show you what I’m talking about. Different rates of discharge were used on the same battery.


Before you can compare batteries, you first need to know where to look for amp hours on your battery. If you are looking at deep cycle batteries, the amp hour rating will be clearly displayed on the battery or on the associated sales information. If the battery you’re looking at doesn’t have an amp hour rating, it’s most likely because it’s a beginning battery, which isn’t designed to supply continuous power in amp hours. Make sure you’re looking at the correct battery type.

What is Watt-hours ?

Watt-hours are another unit that can be used to calculate the battery’s stored energy.

A Watt Hour is a unit of measurement for power over time (an hour), or, it is a method of determining capacity. One watt hour is defined as one watt of average electricity flow per hour. As an example, a 100 Watt light bulb on a 400 Watt Hour battery (like the Yeti 400) would last, on paper, 4 hours.

Volt x Amp-hours = Watt-hours

As you can see in the figure above, both batteries have the same Amp-hours. Is it indicate that they both have the same amount of energy? Nope! The voltage of the battery in Figure 1 is 7.2V, while the voltage of the battery in Figure 2 is 11.1V.

Thus if we calculate their Watt-hours

7.2V x 2.2Ah = 15.84Wh – for Fig 1 battery.                                                                    

11.1V x 2.2Ah = 24.42Wh – for Fig 2 battery.

Thus now it’s obvious which battery has more energy.

The voltage is usually a significant parameter for a battery; after we choose a voltage, the amp-hour rating may be used to specify the capacity. The battery with the highest watt-hour capacity has more energy than the other.

I hope all of you are clear about What is AH Battery and what is a watt hour?.We MATHA ELECTRONICS will be back soon with more interesting topics.

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