Car is 9 years old? Is the battery also 9 years old? Thats one of the first thing i would check.
wiring? when you grounded the wiring to the car...did you scrape all the way down to bare metal, and get a good clean solid connection?
Once you confirm the wiring is right, i would go and have the battery and electrical charging system checked out..and replace the battery if its the original.
Then after those two things are done...you can look at a cap, or doing the big three.