[Kindle Fire 2 Q&A, Help and Troubleshooting] hairyuno:
Earlier this week my daughter handed me her Kindle Fire saying it was hanging on boot and did not seem to be charging.

Background

Originally purchased as a Kindle Fire I replaced the motherboard when the USB socket broke away and it could not be soldered back (pad was missing). I purchase and fitted a replacement motherboard from the US and on arrival it turned out to be a Kindle Fire 2 motherboard.

The only differences apart from the faster processor and more RAM was that the socket for the ambient light sensor was missing. Anyhow I fitted the board and all has been fine for a year.

Symptoms

When switched on it displayed the battery symbol displayed so it was plugged into a 1Amp charger and left overnight. The next morning it was displaying the standard orange Kindle Fire boot logo no animation.

I disconnected from the power supply and did the 20 second power button reset. When it was powered back on each time the orange Kindle Fire logo was displayed with no animation and there it would stop. Disconnected from the power it would stay in the state for over an hour making me think that the battery had a reasonable charge although the charging light never actually went green. Eventually it would go back to the critical battery state as seen initially.

I have repeated the overnight charge process and reset several times with the same results. Whilst plugged in the amber charge light was displayed but never went green.

At this point I decided that it must be because it was not getting past the bootloader and as a result it was not reaching the proper state to be able to charge properly. So I thought it might be a problem with the software and decided to re-flash everything (maybe the battery had died during OTA update I thought) and I purchased a factory/fastboot cable.

I used the tools and images in the KFFirstAide several times using the 10.2.1 and 10.2.3 images (example shown below). But each time the results where the same after a reset the device would either go straight to the static orange Kindle Fire logo or show the battery symbol apparently charge a little at some point boot to the orange Kindle Fire logo.

At this point I am thinking it is a problem with the battery but before I go and spend £30 on a device where I have already replaced the motherboard for $50 and I want to be sure there are no other options, the current used price on ebay seems to be around £50-70 for a similar device.

My daughter is happy to give up on it but my curiosity is piqued and I want to know what is actually wrong and are there any more diagnostics.

I am unix fluent (software developer for 28 years, my first linux distro (slackware was on 40 x 3.5Mb disks!) so if necessary I could switch to using linux tools if that helps.

Is it worth checking the battery with a multi meter?

C:\Kindle Fire Restore\10.2.3>fastboot -i 0x1949 getvar product
product: Otter2-Prod-04
finished. total time: 0.004s

C:\Kindle Fire Restore>fastboot -i 0x1949 flash bootloader otter2-u-boot-prod-10.2.4.bin
target reported max download size of 486539264 bytes
sending 'bootloader' (227 KB)...
OKAY [ 0.234s]
writing 'bootloader'...
OKAY [ 0.047s]
finished. total time: 0.312s

C:\Kindle Fire Restore>fastboot -i 0x1949 flash boot 10.2.1\boot.img
target reported max download size of 486539264 bytes
sending 'boot' (8192 KB)...
OKAY [ 0.515s]
writing 'boot'...
OKAY [ 0.905s]
finished. total time: 1.420s

C:\Kindle Fire Restore>fastboot -i 0x1949 flash recovery 10.2.1\recovery.img
target reported max download size of 486539264 bytes
sending 'recovery' (8192 KB)...
OKAY [ 0.515s]
writing 'recovery'...
OKAY [ 0.905s]
finished. total time: 1.420s

C:\Kindle Fire Restore>fastboot -i 0x1949 flash system 10.2.1\system.img
target reported max download size of 486539264 bytes
sending sparse 'system' (465730 KB)...
OKAY [ 17.940s]
writing 'system'...
OKAY [ 51.563s]
sending sparse 'system' (312222 KB)...
OKAY [ 12.293s]
writing 'system'...
OKAY [ 35.334s]
finished. total time: 117.161s

C:\Kindle Fire Restore>fastboot -i 0x1949 -w
erasing 'userdata'...
OKAY [191.877s]
formatting 'userdata' partition...
Erase successful, but not automatically formatting.
File system type not supported.
OKAY [ 0.127s]
erasing 'cache'...
OKAY [ 76.959s]
formatting 'cache' partition...
Erase successful, but not automatically formatting.
File system type not supported.
OKAY [ 0.140s]
finished. total time: 269.108s