Random false low battery shutdowns on iPhone 4s

I have an iphone 4s that is around 3 years and been heavily used with power consuming location services etc apps so its essentially been charged over night and drained through the day its whole life.

Recently I have notest from 39% or less it will randomly just shutdown complaining of low battery. This tends to be when using the flash or camera at higher levels or just opening an app when around 20% or less.

I have done the obvious battery calibration a number of times with no affect.

Has anyone had similar experiences or suggestions ?