If you’ve ever seen a smartphone or rechargeable battery specification sheet, you’ll likely have seen the acronym, mAh. A common question after seeing that is “What does mAh mean?”. Well, let us explain.
mAh, or milliamp hour, is a measure of the charge capacity of the battery. In other words, it’s how much current can be delivered over the period of one hour. In the case of mAh, it refers to how many milliamps can be constantly delivered over a period of an hour.
For example, a battery rated at 1000 mAh would be able to deliver a constant 1000 milliamps over the course of 1 hour, a constant 100 milliamps over the course of 10 hours, or any other combination milliamps and number of hours that would equate to 1000 milliamps over 1 hour.
What this means is if you have a smartphone that draws 100 milliamps continuously, a 1000 mAh battery would theoretically last about 10 hours. Obviously, smartphones don’t really draw continuous power like that. Instead, smartphones draw less power when idle and more power when in use as additional power would be needed to power the display, wireless radios, the CPU, and others.
Generally speaking, the higher the mAh, the higher the capacity of the battery however, mAh ratings can only be used when comparing batteries of the same voltage and the same type (Alkaline, NiMH, NiCD, Li-ion).
For example, your typical AA battery delivers 1.5 volts while a 2170 battery delivers 3.7 volts. If both batteries had a rating of 1,000 mAh, the AA battery would be able to deliver just 1,500 watt hours (the amount of watts continuously delivered per hour) whereas the 2170 battery would be able to deliver 3,700 watt hours. In terms of total amounts of watts delivered, the 2170 battery can deliver 1.46x the amount of total electricity compared to the AA battery.
Typically, mAh is used as a rating for smaller batteries such as those used for personal electronic devices while Ah, or amp hour, is used for larger batteries such as those used in cordless power tools and kWh, or kilowatt hour, is used in vehicles.