@advocatux It was running Marshmallow before. And yes battery was fine then.
About UT version, I not really sure, It was the default stable picked up by ubports-installer.0.1.20-beta. I am a newbie in UT world, sorry!

I flashed UT on my Nexus 5 a few days back. It's a great experience so far. Just one issue I am facing is with charging. It takes more than 12 hours to charge from say 5%-10% to 100%. This is ridiculously slow. Attaching the charging graph and OS info for reference.