When purchasing laptop batteries, of course the most important factor is capacity. It determines how long and how well your laptop can perform away from an outlet or external power source, and it keeps your machine running in the event of power outages or brownouts as it helps to regulate the current in your machine. But the number of cells in a laptop battery isn’t the totality of battery life.

Most laptop batteries on the market today come in three, six, and nine cell varieties, with six cell batteries being the better balance of battery life and weight. These cells however can actually be of just about any size which can make cell count an inaccurate, or at worst misleading, representation of charge capacity. Individual cells themselves also bear what is called a milliamp-hours rating. This rating is in effect the capacity of each individual cell.

An easier way to think of this is imagining cells as a jug of a certain size. You can half a pint size jug, or a gallon size jug. When looking solely at the number of cells on a battery, all you’re getting really is “This battery contains 6 jugs.” The milliamp-hours tell you whether those jugs are pint capacity or full gallon size jugs. These mAh ratings can range drastically between batteries, typically from 4400 mAh all the way up to 7200 mAh.

When looking at a range like that, you can begin to see how a battery with more cells isn’t always necessarily going to last you longer. This difference becomes especially pertinent when looking at batteries with the same number of cells. For example, if you have two batteries with 6 cells, one with a 4400 mAh rating and the other with a 5200 mAh rating, the second battery will last about 15% longer than the first. Even more notably, a nine cell battery with a 6600 mAh rating will only last about 15-20% more time than a six cell battery with a 5200 mAh rating, but you will pay considerably more for a 9 Cell Battery in comparison with a 6 Cell Battery. When you look at this, it becomes apparent that the most important factor in battery life is the mAh rating, and the cells are just a multiplier.