I changed the alternater and battery in my car.

If th ere is a problem on a wiring circuit, somewhere, for the alternator or battery, replacing them won't solve the problem. Could be you have access drain with everything off. The generic spec is around 50 miliamps, that.050, not even a tenth of an amp. If too much drain, you pull/replace fuses one at a time, when you pull the fuse on the faulty circuit, the drain returns to normal.

If you have a digital multimeter, we can help you check the battery and charging system.