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If you’re only just beginning to learn about batteries, you don’t care about becoming a professional electrician, and you only want to know the bare-bone basics of the Ah on a battery label means, then you’re in the right place!
Let’s look at a simple definition of this mysterious “Ah” in this easy-to-read post!
What Does Ah on a Battery Mean?
First off, how do you pronounce “Ah“?
Ah stands for “amp-hour“.
Example of How To Use Ah in Daily Life
Let’s take a lithium deep cycle battery to understand what that Ah on a battery label means. (A deep cycle battery is just what we call a battery that we can continuously discharge and recharge, like the ones you use in a solar system).
And let’s make this lithium battery a 12-volt / 100 ah battery (which is usually marked on a battery’s label). This is a very common type of battery.
All you have to do is multiply the battery’s volt and its ah, and you get the battery’s watt-hour. So, in the case of our 12-volt / 100 ah battery, you’ll get 1200 watt-hour.
Watt-Hour = Volt x Amp-Hour
So, you can say that our battery is a 12-vol / 100 ah battery. Or you can also say it’s a 12 watt-hour battery.
So let’s take a regular 100 watts lightbulb and you want to light using our 1200 watt-hour battery. How many hours can we light that lightbulb for?
watt-hours ÷ watts = hours
1200 watt-hours ÷ 100 watts = ? hours
12 hours! Easy!
What if you have a 60-watt lightbulb?
1200 watt-hours ÷ 60 watts = 20 hours
And, what if you to use a laptop with this battery? Let’s say this laptop uses 180 watts per hour.
1200 watt-hours ÷ 180 watts = 6.7 hours
So, basically knowing a battery’s volt and ah, and multiplying them together, is a great way of know what and how long you power common things (if you know how many watts per hour they use).
If you want to know more about the nitty-gritty details of what an amp is, check out my post: What Is an Electrical Current?
Is a Higher Ah Battery Better?
A higher Ah battery is not always better.
In the example above, we were using a lithium battery as an example. Now, 12-volt 100 ah lithium battery will give you more electricity than a 12-volt 50 ah lithium battery. So yes, in this instance a higher Ah is better.
But what about a 12-volt batter with 50 ah, and a 6-volt battery with 100 ah. Which is better?
When I compare my batteries, I like to multiply the volt and the amp-hour of the batteries, and then I compare their watt-hour.
So, in the case of the example above:
12 volts x 50 ah = 600 watt-hours
6 volts x 100 ah = 600 watt-hours
The 2 batteries above will each power a 100 watt lightbulb for the same amount of time.
Lithium vs Lead-Acid Batteries
Another thing to consider is that you can discharge (use up) a lithium battery 100% without causing it any harm. However, you can only discharge (use up) most lead-acid battery around 50% before you start to damage the battery.
So let’s say that you have a 12-volt / 100 ah battery. If it’s a lithium battery were you can use 100% of the electricity it contains, you’ll get 1200 watt-hours from it.
But if you take a 12-volt / 100 ah lead-acid battery, and you can only use half of it, then you don’t get 1200 watt-hours from it. You realistically only get about 600 watt-hours from it.
So the amount you can discharge a battery is also something to consider when comparing batteries.