The story is suspect. I don't think the OP realizes what days he's using the phone more and less, or that his usage models at home and work probably vary. Inevitably, he can check his phone as much as he wants at home; maybe less so at work.
During the two scenarios: when was it plugged/unplugged, for how long, etc. I think at home he leaves it off the charger more than at work, where it seems to be plugged in more.
In scenario 1, the phone is unplugged at 7am and is drained by 6pm.
In scenario 2, the first part of the story is irrelevant, the phone is unplugged at 12pm (100% charge). Then does he plug it in that night or not? By the sounds of the story, no he doesn't.
The next day he goes to work and comes home the battery is drained/almost drained.
Consciously or unconsciously he probably used the phone as little as possible on the 2nd day of scenario 2, because in the back of his mind (like anyone's) he's got to be thinking "I can't use this phone too much because it's already been unplugged for a day!"
Conversely, in scenario 1, he probably used the phone more between 7am and 12pm than he realized (that's an extra 5 hours of use on day 1 compared to scenario 2). It's got a full charge, why not use the phone a lot?
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Here's my experience with my G.Nex and GS II :
When you use the phone with the screen on, the phone drains very fast, like 5% every 10-20 minutes. When the phone is unused, drain is usually very slow, like 1% per hour (sometimes less).
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In scenario 1, he's probably checking his emails or other stuff on the phone a few times, so by noon the phone is already drained by 10, 20, 30%. Who knows? Did he use it on the bus/train (or does he drive to work?).
In scenario 2, the phone's usage doesn't even start till noon, then maybe he barely uses the phone (probably so because when he went to bed at midnight the phone had "plenty of battery" left.
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OP -- do you have a program like battery indicator installed that gives you the % of your phone? Because if not, you'd be surprised how much battery 5 minutes of using the phone can drain the battery, or how long the phone can keep an almost full charge if you don't use it at all.
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Try to set up a test where you leave the phone unplugged from 7am to 10pm when you go in to work, using the phone about the average amount you do. Then set up a scenario 2 where you do the same thing when you work from home. Even then, do you use the phone the same amount when you work from home as when you go in to work?