"To drain the battery" means to completely use up or deplete the stored energy in a battery, making it empty and unable to provide power for a device or machine. Full definition
There are corner cases but vast majority of activity isn't going to press past 2 cores and 4 will likely drain battery faster as much as give any increase in performance. (goodereader.com)
It also does not drain the battery in a shocking fashion. (ereadertech.com)
This should offer some good performance from its four 1.3 GHz cores, without draining battery life. (mobilegeeks.com)