When certain condition is met, the phone goes to a state where it is awake 100% of time, even with screen off. The battery drains in less than a day with all hardware off (screen, wifi, blutooth, 3g, gps), sync off, no apps installed, etc. The only way to restore normal conditions is rebooting the phone. Steps to reproduce the problem: insert a microSD card with phone powered off power on phone turn wifi on (and eventually turn it off) The problem persist even if I turn wifi off. There is no problem if I do not insert a microSD, or if I do not turn wifi on (no problem with 3g). Since condition is met, in battery history the "Android System" consumes more than 50%, and the Awake line is blue (on). The BetterBatteryStats app from Market shows 100% Awake time, and ~80% time with a kernel wakelock called "mmc_delayed_work". Eventually, the battery history Awake timeline goes black (off), but according BetterBatteryStats the awake state remains, and the battery drain continues. The following steps did not help to solve the problem: Turn wifi off Turn wifi network notification off Turn off all other hw (screen, blutooth, 3g, gps) Set Airplane mode Format microSD Test different microSD models (1GB and 8GB) Secure extract of SD in Android (but not removing it phisically, that cannot be made without removing battery in Galaxy R) Turn Sync off Uninstall all apps The phone has the stock firmware from factory, I never changed it, nor rooted it. There is no new firmware in Kies for it. Phone info: Model: Samsung Galaxy R GT-I9103 Carrier: Yoigo (Spain) Android version: 2.3.4 Kernel version: 220.127.116.11-I9103XWKG8-CL423654 root@DELL136 #3 Compilation number: GINGERBREAD.XWKG8 PDA: I9103XWKG8 PHONE: I9103XXKG7 CSC: I9103FOPKG2 Build Info: Wed Jul 27 15:38:20 KST 2011 Note: The problem does not happen with a Samsung Galaxy S GT-I9000 with Android 2.3.6.