solve battery low problem of mobile

How to solve battery low problem of mobile phone in an urgent call
Your Mobile Battery is awfully Low, you are expecting an significant call and you don't have a c harger". Nokia instrument come with a reserve battery. To activate the battery, the key-in *3370# your compartment will restart with this reserve and your tool will show a 50% increase in battery. This reserve will get charged when you charge your mobile after that time