What does ah mean on a battery?

When it comes to judging battery life, one of the most useful tools we can use is the battery’s amp hour rating. However, while amp hours can tell us about the battery’s capacity, they don’t work exactly the way you might expect. As with most things, the calculations that go into battery building are more complex than the average person cares to know. Fortunately, we have a quick and easy guide to help you understand what amp hours really mean and how to read them when you are battery shopping.

What is Ah mean on A battery?

Amp hour is the rating used to tell consumers how much amperage a battery can provide for exactly one 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). For large batteries, the rating is abbreviated as Ah. Most deep cycle batteries will tell you the Ah rating at multiple C ratings. The C rating tells you how many amp hours the battery can provide for a very specific period of time. For instance, at C/5 a battery might safely provide 26.8 amp hours. This means that is supplies 26.8 amps in the duration of 5 hours without dropping off. Meanwhile, the same battery may safely provide 36 amp hours for a period of 100 hours. Depending on the amount of use you intend to get out of your battery (daily versus sporadically), you will want to compare amp hours for different C ratings. However, if you aren’t sure which C rating to use, it is best to go with the C/20 because it is the middle ground and will give you a general sense of battery performance.

AH is basically Ampere Hour. An Ampere Hour is the amount of energy charge in a battery that allows one ampere/1000 mAh of current to flow in one hour. The number of amperes can vary with batteries.

We can calculate the amp hour rating of a battery by multiplying the current by the discharge time or we can calculate the amount of time the battery will last while supplying a certain amount of current.

What does ah mean on a battery
12V 100Ah LiFePO4 battery

For example, A 12V 100Ah Battery is used to supply power to a system with a current draw of 100 Amperes.  How long will the battery last?

Using the same equation in the first example we get:

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

100Ah = (20 Amperes) x T

T = 100Ah / 20 A

T = 5 Hours

Thus this battery will power your system up to 5 hours with the continuous current 20A. This is the easiest way to predict how long your battery will last.

The batteries will deliver the as much current as of the load needs. The amount of current that the load draws solely depends on the load. It gives you an estimate of the battery life.


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