This process will show how to unlock your BMW E90 boot if you face following
- locked your keys in the car
- closed your car boot without battery connected or lost power to battery
- Boot not opening through Keys or Latch

Steps to follow
1. Unlock your car if you can
2. Remove the latch on the boot/Trunk using screw driver.
3. Locate BLACK cable between the platic white sheet.
4. Make a metal hook to pull this black cable (this cable ia having rubber insulation on it) I used clothes hanger to make a hook.
5. Using metal hook, keep pulling this cable and keep trying to lift the trunk/boot.
6. Do remember you will NOT hear a click sound. So keep pushing to open trunk after .a pulled cable.