Battery drain issues with apocalypse rom

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http://androidforums.com – While on apocalypse rom battery drains unusually fast after the 15% mark. Overall the battery works quite well but after it reaches 15% mark it just abruptly drains out. Tried finding solutions to the above problem but couldn't get a perfect answer. The situation is too dangerous for me as as I use my phone as alarm clock and it has high possibility that the phone might automatically get switched off during the night. So please reply with a concrete solution as soon as possible. Thanks (General)