I have had this issue a couple of times but today was by far the worst. I was using my phone a lot today and it died around 8 pm. When I got home I threw it on the charger. Once it turned on I noticed the battery indicator was nowhere near zero. The exact percentage was 37%. I've seen this happen several times when rebooting the phone, but the percentage usually jumps only 5%. The phone must not be calibrating the battery level correctly. Is there any way to force battery indicator recalibration besides performing a reboot?