Bmw x3 not holding charge
Hi All, I have a 2004 BMW X3. I changed the battery 3 years ago. Since then I only drove 11,000 km. Since the beginning of this year, if the car parks more than 2 day, I need to jump start. Now the weather is getting colder. Once I park overnight, I need to jump start. Then i bought the battery tender to charge the battery until fully charged. It is allowing me to get 100% charge. If I park for 2 days, it does not allow me to start the car again. can anyone help me? What is the problem?