Game Boy Micro battery upgrade

Can you play your Game Boy Micro for several hours? I can't till now.
This blog is all about diy, so let's make a new battery for it.
In my region original battery cost a lot and I searched for similiar size lithium battery.

 And found this 9v rechargable lithium battery.

I thought there are 2 3.7v lithium cells in series inside and I was right. You can actually build two batteries for the price.

Protection circuit inside which prevent deep discharge and overcharge.

I cut out protection pcb and split battery cells.

Then I unwrap original battery to compare old and new cell sizes.

Checking how it fits inside Game Boy Micro.

New cell is half mm thicker, but it's a no problem.
Then I soldered wires from original battery and tested charging and playing.

I also added a sticker from original battery, so it looks almost original =)
New cell has a bit more juice too. Works and chrages great, as expected. Battery cover sits ok.