Topic: DS battery only lasts 1 hour . . . what to do?

Ok,

Our oldest DS' battery only lasts about an hour now.

I've replaced the battery with a new (non-OEM) one and it doesn't help.

And I've taken the Nintendo battery out of our newer DS that still gets about 3 hours and tried that battery in the old DS, and still, the old DS only lasts an hour or so.

So . . . I don't think it is the battery.

Questions:

1) Does anyone know why our old DS is only getting about an hours playtime, even with a new (non-OEM) battery, or known-good-battery from another DS? Is there another test to do on this DS? Is there any easy fix to this?

and . . . I know if I plug the DS into a USB-Battery-Pack it lasts a long time, so I've bought a really small USB-Battery-Pack and I was going to just "Velcro(TM)" it together . . . so this bring me to my 2nd question . . .

2) Does anyone know of a DS case that incorporates a battery pack to lenghten your game time?

Any help greatly appreciated!