Ok, so this is a classic problem, phone won't start due battery charge too low. People seem to recommend playing with flasher to get some charge to the bat, but here is alternate solution which won't risk your data as much.

You need a lithium ion charger, I had Nitecore i2 for 18650 type batteries and multimeter cables. Just attach cables to charger and hold measuring tips on battery terminals for 10-15 minutes carefully avoiding short circuiting and reverse polarity. I had battery attached on the phone while doing this, take it out if you like to have lower failure risk.

Picture:


Disassembly guide:
http://jollan9story.wordpress.com/20...placement-diy/