Battery goes almost dead if car sits for a week not driven. Car got driven daily until son left for Navy BMT. Do I need a trickle charger or a mechanic ? Ive had other sports cars that did this but usually took about 2 weeks not a week..

 

1 week, 2 weeks. Something is wrong. Get a new battery

 

OP never mentioned how old this Z's battery was. Anything over three years old is suspect with a lead acid battery.

 

3 years. Batteries are crap these days I guess . But If I disconnect the neg battery cable it doesn't loose charge.

 

You have a parasitic drain. Could be a computer module failing to go to sleep. Check out an Amp Hound tool to diagnose. Otherwise take it to a pro to find the source.

Obvious things to check would be aftermarket wiring and electronics. Stereos, alarms, lighting mods, etc. Another option to try would be pulling fuses one at a time. Trial and error method. Best done with an Amp Hound watching current draw on battery.
Good Luck!
-Icer

 

Yeah I figured. It has an aftermarket pioneer stereo/navigation. Professionally installed..

 

Does the aftermarket stereo have a discrete amplifier with a large +12V cable connected directly to the battery? Or is it just the head unit in the dash?

Not saying the stereo is definitely the source of the drain, but if not wired properly to ignition power, it could cause a parasitic drain. If an external amplifier is part of the system, there's supposed to be a "Power Control" wire going from the head unit in dash to the amplifier. This wire is crucial for turning on/off the amplifier with ignition power.

There could be many other causes of parasitic drain, a common one on the Z is if the brake switch rubber bump stop cracks and falls out, then the brake lights will be stuck on 24/7. The bump stop contacts the switch when you release the brake pedal, without the stop in place, the car thinks you're pressing the brake pedal and thus keeps your brake lights on, even with the vehicle off and keys out of ignition.

Hope this helps!
Cheers!
-Icer