My friend was facing the problem with his cellphone's rapid battery drain problem. According to him,battery used to hold single day power even after heavy usage, but it was just 6 to 7 hours. When I saw his application list, it was huge! Lots of shopping, social networking, and messaging apps. I was not sure which one was eating the battery. I suggested him to remove the unused apps. It was still the same. In settings menu, the running applications were of Google and Facebook. I was ignoring Facebook app because everybody uses it. But after removing Facebook app, the cellphone was breathing a new life. Battery drain reduced. Now, we knew that Facebook's official app is the cause of heavy battery drain and I read the news "Removing Facebook App increases battery life by 20%". Just the day after we removed it. But there was was a need to use the Facebook on mobile phone.
The cheap and easy alternative is to use the browser to check the Facebook. I am fan of F-Droid and found a simple app called Face Slim. It is just like opening browser and very lightweight. If you want messenger, then this app is not for you.
I recommend installing F-Droid first and then Face Slim. You will get regular updates.