Alright,
my GBA died some months ago.
I figured it was the battery, Because It had swollen.
Turns out I was right!
Our wireless phone died recently.
So I decided to wire the nickle metal Hydride Battery into my GBA
It powered up and booted the flashcard!
The final thing now is, Will it charge?
My bet is No.
But...I will try to find out anyway.
The official GBA battery output was 3.7
the Phone battery is 3.6
only a difference of 0.1.
Not to mention that the Charging system on the GBA is for a lithium battery instead of a Nicd.
Its a risk, And I have a fire extinguisher ready for the worst case scenario.
Just need to drain it first.
Wish me luck.