What do battery codes mean?
 

Most cell phones these days use Lithium-ion batteries as their main power source. A cell phone needs to be charged by using a charger. If you have a Li-ion battery then you have to ensure that the charging of your cell phone is done only when it is fully charged.
There are many other types of batteries that are used by a cell phone, for example, Ni-Mh, Ni-CD, and Li-Fe. To charge the Ni-Mh battery, you need a Ni-Mh battery charger and to charge the Ni-CD battery, you need a Ni-CD battery charger. Similarly, the Li-Fe battery charger is used to charge the Li-Fe battery.
Battery codes
A Battery Guides is used to identify the type of battery in a cell phone. There are four different types of battery codes:
The low voltage code is used to identify the amount of power stored in the battery.
The capacity code is used to identify the amount of energy that is available in the battery. If the capacity of a battery is low then it will be given a low capacity code.
This is the last step and it is used to identify the amount of energy that is left in the battery.

Battery group size
 

There are also battery group sizes which categorizes based on the dimensions. The tool might help lookup the dimensions of the battery you are looking for