The one Sonic is showing is an external. Your still limited based on the original battery.
@Sic Wario
It is just an cover replacement with a slightly larger battery. Removing the battery for extended periods of time can make the 3DS lose the settings and configs that are stored in RAM to be erased. Example is the date and time, there are several games that use that and changing it would cause a few errors.
@jrmaxnj
What specific battery pack are you refering to, that is only a filtered search.