What exactly do Amp Hours tell you about your battery’s capacity?

The language of batteries can be complex. If you’ve ever found yourself confused by the ratings, acronyms, and lingo associated with batteries, you’re not alone. 

But understanding the differences between a battery’s voltage, amps, and electrical current is something incredibly valuable to know! If you’ve ever picked up a battery and wondered if it has the life needed to power your device, understanding the Ah on a battery helps you choose the best battery for your needs.

What Is An Amp?

The Ah refers to “ampere-hours,” “amperage-hours,” or simply “amp hours.” This is the unit used to measure how much energy a battery has. This rating describes the discharge current that a battery can output at a specific rate for a measured amount of time—typically an hour.

The amp-hour rating is used for all different types of batteries, such as car batteries, rechargeable batteries, and single-use batteries.

The length of the battery life will also vary depending on factors like temperature, discharge rate, and the age of the battery.

What’s the difference between Ah and Volts?

It’s important to understand the difference between battery voltage and amp hours, as they are very different! Each one performs its own purpose, and together they work perfectly to power your needs. 

Essentially, Ah is what determines the lifespan of a battery, and volts determine the power. 

Common Ah Ratings

Batteries can range from as low as 0.1  (some coin cell batteries), while larger batteries, such as a 12 Volt, can have up to 1,000 Ah! Always check your device’s amperage before choosing a battery, but if you’re worried you’re using a higher Ah than needed, don’t worry. 

It’s better to use a battery with a higher Ah than one with an Ah that's not high enough. This is because you don’t want to risk running out of power!

Let’s look at some common Ah ratings:

Alkaline Batteries

Typical household batteries vary in Ah from 0.1 to around 20 Ah. Here’s a breakdown of the typical amperage level these batteries have. 

• AA alkaline batteries typically have an amperage level of 2–3 Ah. 
• AAA batteries range from 0.5–1 Ah. 
• C batteries have an Ah of around 1–7 Ah. 

• D: Typically around 1 to 20 Ah.
• 9V: around 0.5 to 1 Ah.

Lithium-ion (Li-ion) Batteries

Lithium-ion batteries, also known as li-ion batteries, are designed with amp-hour ratings depending on their intended use case. Some common ratings for electrical devices range from 1 Ah to 3 Ah for an application such as smartphone batteries, while larger applications such as electric vehicles have an Ah of 10 or more. 

Lead-Acid Batteries:

A lead acid battery is a type of rechargeable battery, actually the first one ever invented! It is still commonly used in vehicle starters, small power sources, and UPS (uninterrupted power supply) systems. 

Common Ah ratings for this kind of battery are around 40 to 100 Ah for car batteries, while deep cycle batteries (such as marine batteries) range from 50 Ah to over 200 Ah.

Does Higher Ah Mean Better Performance?

When it comes to amperage levels, is more or less best? If you’re trying to figure out a device’s amperage and are still unsure which Ah it requires, more is always better. So if you know around how many amps you need but aren't sure, just lean towards the higher side.

One of the most common questions is: does higher amperage mean better performance? Actually, amperage refers to a battery’s capacity for runtime hours; it’s voltage that determines performance!

This means that if you’re looking for a powerful battery, you’ll want to get one with a high voltage. If you're looking for a battery with a lot of life in it that can provide a charge for a long period of time, you'll want to get one with a higher Ah.

It’s important to keep your batteries out of the heat and cold as much as you can, due to contact with temperature swings impacting and shortening a battery’s lifespan and performance.

How to Calculate a Battery’s Capacity

Battery capacity is measured in ampere-hours or milliampere-hours (mAh) and indicates the amount of charge a battery can store and deliver over a certain number of hours before reaching the end of its lifespan.

There is an easy formula that you can use to calculate a battery’s capacity: Capacity (Ah or mAh) = Current (A or mA) × Time (h). 

Current is the electrical current flowing through a battery, and time is the duration of hours. Once you multiply these together, you will have the result of a battery’s amperage hours!

The Ah on your battery is referring to the discharge period of the amps of current the battery cell can discharge within an hour.