If you have a weak battery and it is not charging anymore, then you need a repalcement battery.
There are two official models of PS3 Controllers. First there was the SIXAXIS on the market. Later SONY released the DUALSHOCK3, which have a additional shock function.
The battery we offer here are for the older SIXAXIS model. They won´t fit in the DUALSHOCK.
To exchange the battery is easy, you won´t need more than a screwdriver and a little patience.