What does mAh mean?
When we talk about rechargeable batteries and their duration, we often refer to mAh.
But what exactly does it mean?
First of all, it’s important to know that mAh is the abbreviation for milliampere hour, namely the 1000th of an ampere hour (Ah).
Ampere hour is the amount of energy stored in a battery that allows one ampere of current to flow for one hour.
But, if we omit specific technical definitions, the mAh represents the capacity of a battery to store energy as it specifies the measure of battery life before it needs to be recharged.
What is a milliamp hour
We’ve already said that mAh refers to the battery’s energy storage capacity, but what does it specifically mean?
Well, the milliampere hour is a unit of measure for the electrical power over time, generally used to describe also the amount of energy a battery can store.
We therefore use mAh to describe the capacity of small batteries as the bigger ones are labeled in ampere hour.
From a practical point of view, the mAh allow us to distinguish a battery’s strength from its capacity: higher the milliampere hour is, longer the battery will last (but it will also be physically larger).
In the specific, a higher mAh means that a fully-charged battery can power up a device that consumes more energy than another or that it can have a longer lifetime before it needs to be recharged.
For example, a battery rated at 2500 mAh can power a device drawing 100 milliamps for 25 hours or 250 milliampere for 10 hours.
How to calculate milliamp hours
We’ve already said that battery life is calculated based on the current rating in milliampere hour (mAh), but how can battery ampere be exactly calculated?
Well, battery capacity is calculated taking into account two different variables: the current rating in milliamp hour and the load current of the circuit.
So battery life will be high when load current is less, and vice versa.
And this is the math formula to use:
Battery life = Battery capacity in mAh / Load current in mAh
In this way, in addition to knowing the measure of battery voltage, you can also know how long the charged battery will last.
For example, if we talk about a circuit connected with 600 mAh current rating and related to the load of 30 mAh, we can calculate that the battery will last roughly for 20 hours.
The calculation is simple and it can be done by everyone, obviously knowing the two reference measurements.
How to measure mAh
Once given the correct definition of mAh, it’s important to understand how to measure the milliampere hour.
You can measure this value by using a multimeter, a load-bearing resistor and a stopwatch to measure elapsed time.
The steps of this operation are quite simple but require great precision and attention.
If you want to test a lithium-ion battery, you must first recharge it completely.
Then you have to turn on the digital multimeter and set the measuring dial to the DC (Direct Current) setting – usually indicated by the capital letter “A”.
After this make sure to connect properly the multimeter to the battery.
Check the reading of the current on the multimeter screen, note it down on the sheet of paper and activate the stopwatch.
Then you just have to wait and turn off the timer when the device is charged and the battery life is over.
When the battery is completely discharged, you can calculate the time in hours required to drain it.
At this point you will only have to multiply current rating by the time to measure the battery capacity in milliampere hours.