[honerboys]

sounds like a drain on the battery - i had a bad rear hatch switch and it would let the interior lights stay on - which i didn't notice in daytime - would kill battery - but not overnight - if you have a clip on ammeter - put it on the positive battery cable and see what it's drawing with everything off - should be negligible - if it's not remove fuses one at a time until you find the circuit that's pulling the amps - go from there - would be weird to get one bad battery after another - only things i can think of in a 928 that draw when car is off would be clock and radio memory - is your alternator charging when it's running?