My Lg g2 have a red flashing led but not start

Hello everyone,

I'm here because i've a little problem with my d802. Few months ago, i've break my motherboard (i've shorted the capacitors with a screwdriver.. -_-). But now i've buy a new motherboard for my lg g2, she was tested and she work.

I've an idea but not sure if it's the problem : I've don't use my phone and the parts during a long time, may be the battery was drained at 100% and she die ?. anyway, have you got a solution for this problem ?

Thank you in advance, sorry for my english if it's not 100% understanding but i'm french and don't use english all the time.

Thanks for reading me