Actually cell phone doesnt utilize total amount of battery just like our laptops.
In laptop, it automatically shut downs/hibernates system based on pre-defined battery level. Like when the battery reaches 3% power, the laptop will automatically hibernate/shut down. But u can change this 3% level from Power Settings.
Same case applies in cell phones, it automatically switch off at a pre-defined battery level. And u can decrease this level and can allow cell phone to fully utilize the battery by using such codes.
But such codes don't give noticable amount of battery backup, just a few extra minutes, which are hardly to notice.