This is strange. Had my Razr off the charge for only 30 mins and it's down to 95%. Not much running either.
Sent from my Motorola (Droid) Razr Maxx.. out in the boonies of TN while picking on a guitar!
This isn't as strange as it may seem. Once the battery is fully charged to 100% (whether on or off while charging), the charger shuts off all power to the battery and goes into standby to prevent overcharging and doing harm to the battery. This can be proven by looking at the battery icon while on. If it has a lightning bolt on it and it's changing from almost solid green with a small portion black to solid green, it's charging...and if there isn't a lightning bolt and instead it's solid green 100% of the time, it's in standby.
Then if the phone is on, it is now pulling power back out of the battery even though it's still "plugged in". If it remains plugged in and on, it will continue depleting the power of the battery until the meter reaches 90%, at which point it will resume charging to "top off" to 100%, and then resume standby mode and start the watch and wait process again. With a phone on while connected to the charger, this can happen several times over a night's sleep, and when you remove it from the charger, it can be anywhere from 100% to as little as 90% charged to capacity depending on when you disconnect it. In your situation, you may have pulled it off the charger when it was already partially depleted and then in the 30 minutes you had it disconnected from the charger it "seemed" to draw 5% of the power. Also worth noting, if it shows 95%, that means it has AT LEAST 95% but not 96%, so it can have 95.5% or 95.9%, but will show 95% until it reaches 94.9% at which point it will show 94%, and so on.
Another interesting and strange effect these batteries have is the fact that they drop in available voltage rather quickly during the first 20% or so of charge from capacity, then the voltage levels off for about the next 60% or so, and finally starts to drop rapidly again during the last 20%. This is of course, assuming the charger and metering system have been properly calibrated to the battery's actual capacity (charging to 100% with power off, using to 15%, and then charging to 100% with power off again).
The same holds true even if the phone is powered off, however it will obviously not deplete anywhere near as quickly as it will while still powered on and connected to the charger but on stand by. Still, you might have pulled it off the charger during a power-off charging cycle while it was in standby mode, and it could have already lost as much as 2 to 4%, which would then correspond fairly to the 95% level after 30 minutes of use.