Based on phone in pocket, screen off all day...
Monday - Phone dead by 2pm
Tuesday - Phone would have died by 4pm according to battery graph.
Wednesday - Current battery graph shows predicted death at 4am (AM!)
On Monday night I had a huge cull of useless apps. No real difference.
On Tuesday night I topped up my prepay account, and got my mobile data plan back online after a few days without it.
Speculation: My phone was repeatedly trying to connect with 4G data (since I wasn't near wifi all day) but being rejected by the network. (Possibly also boosting the radio signal in an attempt to handle a perceived low coverage area?)
Correlation does not imply causation. But if anyone else with battery issues since upgrading to Lollipop can pin it down to a similar cause, then I'd love to know. Might be worth a bug ticket to the Googs.