After driving car with new battery couple days later car wont start.

Have the alternator tested,Also have the battery tested to make sure you have not gotten a faulty one, IF the battery loses charge over time,you may have a wiring short cicuit that drains the battery, Make sure all lights are off,including the glove box light when car is off. I have had to replace the alternator 4 times on my 02 Kia due to factory defect alt.Had bench tested(good) 3 times,but would not work in the car.Mike