3100 and wrong battery charge level

[vastar]

I have Nokia 3100 almost one month. And I have a problem with it. Phone shows wrong battery charge level. The first 3 days it shows maximum charge level. Then charge level decreases until minimum very quickly (about 12 hours). Version of software is 5.02, battery type is BR-5C. Should NOKIA replace my battery? Can anybody help me.

[TheTool]

I have the exact same problem with my 3100
software version: 4.01