Canada FUJITSU 'f' Series Laptop Computer Battery

Can I replace 18650 cells in a laptop battery with a higher capacity?

The short answer is technically yes, mAh only refers to power capacity and how many milliamps the laptop battery can deliver per hour. The more important compatibility measurement is the voltage it supplies. As long as the voltage is close it should work.

Most laptop battery makers advertise their batteries power capacity in terms of 4400, 5200, 5600 or 5800 mAh. The basic idea is that 5800 mAh battery pack will allow your laptop to run longer than a battery with a 4400 mAh rating. Generally speaking this is true, but it is not the whole story.

Lets say your laptop need 20 watts of energy to run per hour. A battery pack that stores 60 WH (watt hours) will provide you 3 hours of run time. So where does mAh fit in to this equation then?

Answer: millamps(mAh) x voltage (V) = watt hours (WH)

Example 1: 2200 mAh x 14.8 V = 32.56 WH (theoretically around 1.5 hours)

Example 2: 5200 mAh x 14.8 V = 76.96 WH (theoretically around 4.0 hours)

But lots of other factor will play in as well, for example the type of usage, application being used? If you’re playing games, let’s just assume that the run time will be lower.