With ds>3ds the contacts you mentioned, inside the console, lose their tension over time. Because the battery is pressing against them constantly. This is the usual suspect.
[image|3247558]
Use a hooked tool, I use a small safety pin that I bent the tip on. Gently tug the tabs, in pairs, out just a little. Like so:
[image|3247559]
This will restore solid contact between the battery and the console.