battery always at 100 percent

I recently changed the battery in my iPhone 4S as the old battery was only lasting 3 hours. Since doing this the percentage indicator and battery sign is constantly showing fully charged or 100 percent. The battery is fantastic and lasts nearly 2 days with light usage but I never know how much charge is left on the battery have I damaged a component when installing the new battery or is It a faulty battery or am I completely missing some thing. Any help would be greatly appreciated thanks in advance