all warning lights came on

94 J-30

Last ngiht I was driving all my warning lights came on...
My out side lights were on bright but went to dim

As driving the out side lights all most went to no lights.
HAd very little power to pull the car.

THe battery is brand new. Got it last week

any ideas???

WE TOOK the battery to have it tested, it was fine

took the altinator to be tested it was fine

so why will the car battery not stay charged?