Listen to radio without engine running or draining battery

Try not putting foot on brake when touching button? Brake is required in Mercedes

Worked thanks much, any idea whether it'll drain battery? Would be on for least 2 hours

Using battery power drains the battery. If you are concerned about this you should check the amp hours of the battery the car came with. Chances are it is an el cheapo battery with limited power. If you plan on playing the radio for long times you should invest in a heavy duty, high capacity battery such as an Optima or Odyssey.

Of course it will drain battery. Probably not enough to stop car from starting but its possible if you leave ignition on (especially with radio playing) long enough. Simply start car on occasion while listening, run for a couple minutes and turn back off. You should be ok.

Yes the battery will drain

What do you do when it drains? Jump it right?

If you want to listen to your radio or play your music without the Nissan battery saver message coming up and the car shutting off itself to save battery. You have to press the start button once for ACC MODE, then put the shifter into N. This will prevent the car from shutting on its own as it is thinking that the car is in Drive, instead of PARK . I have a 2nd battery for music so it last for almost 4 hours, then I just start the car for a couple minutes to recharge up the battery