Just to confirm - your bootloader is "Locked", yes?

Do you have access to a PC/laptop with the adb/fastboot tools installed? You can get the mini-SDK here if not:

ADB Guide (updated 2014/11/11)

along with instructions to install.

Reboot phone to bootloader in FASTBOOT mode and plug in to PC (so you see FASTBOOT USB on bootloader screen). If bootloader is in FASTBOOT this will be highlighted in blue just below the green bootloader information lines. If this shows HBOOT, then make sure FASTBOOT is highlighted from the menu of coloured text items below this - it is usually already highlighted - if need be use vol up/down buttons to highlight FASTBOOT and press the power button to select it. The bootloader will boot to FASTBOOT.

Open a command prompt window in the adb/fastboot folder on your PC - if in Explorer hold shift + right click, and pick "Open command window here" from context menu.

Then type:

fastboot devices (this is to check fastboot connects to phone ok, it should also return the phone serial number - write this down carefully as we might need it)

If it does, then type:

fastboot getvar all

and post the info the command returns but scrub out your IMEI number and serial number.

Note that if your bootloader is "Locked", unfortunately we may end up in the situation where to get phone working again the process involved wipes your phone including the internal SD card.

 

Good luck man. I've been there and it's scary as hell so I know.

I will say this, you shouldn't need to wait for the battery to run out to reboot. If you're trying to get to the bootloader and you have a black screen, you can try this.

Normally, doing a Press/hold the power button and press/hold the volume up button for about 10 seconds will simply reboot the phone. However, if you're trying to reboot to the bootloader, you can try this.

On the 10th second of holding the power and volume up, without releasing the power button, quickly release the volume up and press/hold the volume down button. It might take a few attempts but if it works, it will get you to the bootloader. I've tried it on mine a few times and it worked for me.