First of all, the 18650 battery used in notebook computers usually has a capacity of 2200 mAh (milliampere-hours). It can be explained as follows: a 3.7V voltage and 2200mA (milliampere) current supply can be used for 1 hour. The higher specification capacity is 2400mAh, 2600mAh (mainly Sanyo batteries, Sony notebooks mostly use 2600mAh specifications). 
The following uses a common 3.7V/2200mAh cell as an example. 
One, usually said three-cell battery that is formed by the three 18650 batteries connected in series. The battery is finally labeled 11.1V/2200mAh. 11.1V=3.7V×3, the output current remains unchanged at 2200mAh in series. 
There is also a reference of 10.8V, that is, a single cell has a voltage drop that causes the total voltage to drop. 
The popular netbooks on the market now have more battery packs for this specification. 
Second, four-cell battery There are two cases: four series and two strings and two. 
The final marked parameter for the four series battery packs is: 14.8V/2200mAh. 14.8V=3.7V×4, the output current remains unchanged at 2200mAh in series. 
The two strings of two batteries are divided into two groups, ie, four batteries, and the two batteries are connected in parallel. The final marked parameter of the battery pack is: 7.4V/4400mAh. 7.4V=3.7V×2, the output current is 4400mAh=2200mAh×2. 
The medium-sized notebooks (12.1 inches, 13.3 inches, etc.) currently on the market have more battery packs for this specification. 
Three, six-cell battery, generally three strings and two, that is, six batteries are divided into two groups of three, three and three series and then parallel. The battery's final indicator is 11.1V/4400mAh. 11.1V=3.7V×3, the output current is 4400mAh=2200mAh×2. 
Some high specification notebooks use six-cell batteries. 
Of course there are more than six-cell batteries, such as nine-core and so on.