I am going to a car show soon and was wondering how long I could leave the D3 running without turning on my car and it not drain my battery? I wanna play a dvd while the car show is going on so they understand what the D3 does.

In the shows I've been in I bring at least one extra battery or if I can I put a car charger on my battery during the show.

Exactly how long you can run the unit on your battery depends upon many factors...

The size of your battery.

The type of battery.

The condition of your battery.

The draw of other devices in your vehicle.

Temperature.

I can run my D2 with a DVD player & the key turned backwards for about 4 hours before my battery goes down.

My solution was to buy an optima yellow top battery, it's amazing and is meant to be deep charged after a draining usually from carshows, etc. . Starts up the car like a champ all the time after a few hours using the radio, lighting, etc.