I second the suggestion to do some proper recharge cycle.
If i were you, i'll test this way: fully charged, power on, and then put it immediately in stand-by (by clicking once on the power button) and left it there. It has to use almost nothing in this configuration. If not, there is some problem with the fw.
In my experience, the first thing to check with smart "mobile" devices is standby battery. Checked that, you can explore further.