Quick Question: Will my car run out of battery if I turn on ALL these (LCD, DVD, FM Mod.) WITHOUT starting the engine?
1. LCD and FM modulator are getting the power from the fuse box,
2. DVD player is getting power from the cigar. lighter
THANKS FOR YOUR HELP!!!

 

please help this poor guy.....i really need an answer.
How long will the battery last without starting the car?

 

If your engine's not running, then all electrical appliances are running off of your battery (not the alternator), regardless of how those electrical devices are wired (via cigarette lighter, directly from the battery--doesn't matter). How long your battery will last depends on what battery/batteries you are using, how much total current ALL electrical devices are drawing, and how long you run them. Assuming you are using the stock 350Z battery only, and guesstimating the current usage of the described items, you should be able to run them for hours (several) w/o a problem. Further, the next time you start the car, your alternator should help to recharge your battery. Having said that, the longer and more times you run things straight off of the battery, the shorter the life of said battery will be.

 

Does the battery gauge work with the ingnition turned without the car on? If so my car is usaully around 14 volts If you see it get lower then 12 start the car.

 

Yep . . . that's true, too.