Battery Issue?

[bpv35]

Hey guys, this topic may have been covered else where in this forum, however I was unable to rectify my issue via a simple search. Hence, I was hoping someone could point me to the right direction.

I have a 2003 350gt, coupe and lately I've been having some strange issues. I believe it is caused by the faulty battery.

After I have left my head lights on and killed the battery I jump-start it and it continued to work. A few days later, I was sitting at a intersection where my car suddenly turned off and then my alarm would go off and then immediately all electrical powers shuts down. I have to restart my engine for the car to run again. Initially, I thought it's only a minor issue but it has happened again and again. I continued to ignore the issue.. until today. I was at the shopping centre where I got into my car via keyless entry and attempt to start my car. Unfortunately I have lost all power without any warnings. My car was dead. Usually without the key I could still adjust my electrical seat but this time I couldn't. Also, my alarm was going off at a very LOW LOW! pitch. I opened my door and the alarm stopped. Weird! So I tried to close my door again and once again it went off.

I sat there for about 15minutes and all of a sudden.. the alarm went off. But this time it was loud! the car regained electrical powers and the light inside the car turned on because i had my door opened. i tried to start the car and it works!

so my ultimate question is.. do i need to replace my battery? If so which one do i need? Which brand? What CCA?

thanks and sorry for the long essay!

Bee