1986 Cadillac Fleetwood VEHICLE DIED @ FREEWAY SPEED

I WAS DRIVING AWAY FROM AN AUTO AUCTION LOT WHERE I BOUGHT A '98 FLEETWOOD CADILLAC. IT SEEMED TO DRIVE FINE, BUY 8 MILES DOWN THE ROAD THE CAR SEEMED SLUGGISH IN ACCELERATING. TRAFFIC VARIED BETWEEN 35MPH TO 65 MPH. WHEN TRAFFIC CLEARED, THE ACCELERATION SEEMED MORE AND MORE LABORED. EVENTUALLY THE CAR STALLED AFTER I LET OFF THE ACCELERATOR, AND I PULLED TO THE SIDE OF THE ROAD. AFTER RESTARTING THE CAR, I PULLED OUT AGAIN TO FIND LABORING ACCELERATION. AS SOON AS I RELEASED THE ACCELERATOR THE CAR STALLED AGAIN. I RESTARTED IT IN NEUTRAL WHILE COASTING, BUT AGAIN IT STALLED WHEN I RELEASED THE ACCELERATOR. I PULLED OFF THE FREEWAY, AND TRIED TO RESTART THE VEHICLE. THE BATTERY EVENTUALLY WAS TO WEAK TO TURN OVER THE ENGINE.