My Sony Ericsson K310i used to discharge in a week when turned off with a SIM-card present and only lose 5% in a month when turned off with SIM-card removed. A

My Sony Ericsson K310i used to discharge in a week when turned off with a SIM-card present and only lose 5% in a month when turned off with SIM-card removed. At the time I thought it was due to poor power management, but now it really makes me wonder.