Thanks for making this guide, this exact issue has been troubling me for a few days now. I had already bought a new battery which charged once but has the same status now, and this thread also confirms that battery is not the issue. Now, I am trying to follow the steps to get the device working once to check whether the issue on my xperia Z is the same as what quickstyler suggests (Many thanks for the hardware fix, quickstyler) before trying any soldering on my phone.
I am able to get into fastboot mode, but when flashing system.sin, fastboot returns an error : remote (data too large). Even after lots of googling and searching on xda (tried different fastboot binaries, but none helped), I am none the wiser on that error. Any chance you guys encountered that error or have a solution?
Also, if this error cannot be resolved, can fixing the charging circuit hardware get my phone in flash mode as I have erased /system on my phone.
Make sure your in FlashMode not fastboot mode as @quickstyler mentioned and regarding the hardware fix i didn't have any free time to try it but its a logical fix to the problem i already disassembled my device and going to solder the wire in a bit