Researchers at Purdue University, Intel Corp and startup company Mobile Enerlytics studied the use of 2,000 smartphones served by 191 mobile operators in 61 countries.
    
"This was the first large-scale study of smartphone energy drain 'in the wild,' or in everyday use by consumers," said Y Charlie Hu, professor at Purdue University.
    
Out of the 45.9 per cent of daily battery drain where the screen is off, 28.9 per cent is due to apps that frequently wake up and run in the background, the researchers said.
    
Out of this 28.9 per cent, researchers have shown how to save 15.7 per cent with a new system called HUSH.
    
"During screen-off, the phone hardware should enter the sleep state, draining close to zero power," Hu said.
    
"Apps wake the phone up periodically during screen-off to do useful things, but then afterward, they should let the phone go back to sleep," Hu said.
    
"They are not letting the phone go back to sleep because of software bugs and, specifically, due to the incorrect use of Android power control application programming interfaces called wakelocks," Hu said.