Just got my Z8 about 3 weeks ago and twice, after being left once for 10 days and once for about 5 days, the battery was totally dead. It recharged both times, although to what level I don't know, but would start 2 days later. I first thought that the phone might be staying on, but that's not the case. The car was locked and alarmed in both instances. Anyone else had a problem like this?