Help Android Update drains battery like Water.

[Android Question]

OK, so I was fed up of eating KitKats so decided to luck some lollipops and updated it through CynogenMod and everything was fine till next 24 hours but when I charged my phone to the full and left home for a 30 minutes travel and it drained 15% of battery without any tasks running even not in the background.
Any help will be appreciated.

 

[Hadron]

There are always tasks running on a phone.

You could just give it a day or two. After a major update the system needs to relearn your usage, so I would expect the battery life to be poorer for the first day or two. If it doesn't improve use a better battery monitor than the built in one (GSam is a popular free choice) to find what is using the power, or try a different ROM (I've not used CM since version CM7, but it was never the most battery-efficient ROM out there). Or visit the rom development thread (e.g. on XDA or the CM forum) and see whether others are having similar problems. Remember that the rom must be built for the device, so it's possible for a problem to be specific to that rom on that device, rather than a general lollipop issue, and as you've not said what device you have we can't offer any specific advice.