Did you replace it with the correct battery? Are you sure the alternator is correct for your car? Are you leaving anything running like interior or exterior lights? Maybe you have a short somewhere in your wiring harness. The "More Questions" response is totally off base as none of those things are causing the problem. The problem was there before the battery and alternator replacement, and it's still there. A short circuit would either blow a fuse, or burn up a fusible link, neither of which have been reported by the questioner. This case is a good example of what not to do in trying to fix any problem. Obviously you spent good money to replace parts which were NOT defective. This is what I call the "shotgun" repair method. The proper way to correct any problem is to properly trouble shoot and DIAGNOSE the CAUSE of the problem, thereby allowing for the quickest, most efficient, and least expensive repair or replacement of the guilty component. There are other possible causes for the failure issue described in your question. Those I can recall include: 1. Defective battery cables, clamps, or connector terminals at the either end of the cables. 2. Corroded interface surfaces at any connections. 3. A defective starter solenoid. 4. Even a defective starter, including an accumulation of starter brush "dust" between the brushes and the commutator contacts. I suggest that you take your vehicle to a QUALIFIED auto mechanic, or auto electrical technician, who will be able to identify the specific cause of the problem, and most economically accomplish only the necessary repair or replacement. j3h.