If you have a NVIDIA Shield controller that battery has died here you can check how to open and assemble the controller and either replace the battery with a pre-made pack or DIY one with 2 Ni-MH AA cells (Nickel - Metal Hydride) which is way cheaper but more challenging. If by any means you don't have the tools or knowledge to achieve this safely please do not proceed as it can be dangerous to work with battery cells - just buy the pre-made ones. DO NOT ATTEMPT THIS TECHNIC WITH LITHIUM BATTERIES.
