Drive-in cinema other than having the car on all the time?

I wanted to go to the drive-in on Friday, but I'm afraid that my battery won't last from the car that long. Because of the current situation, you can't borrow a radio from there.

And on my cell phone I don't find a radio, I have a Huawei p30 either tips where I can find it or with which you can set the radio frequencies.

Since you can hear the film with a radio frequency

It is enough if you have the ignition on. In the two hours for the film, the battery doesn't go dead.

Ignition off → simply switch on the radio.

It does not work?

The battery does not drain so quickly. If you only switch on the ignition so that the radio or electronics work, it will take hours until the battery would run out. If it were otherwise, nobody would visit something like this with their car.

Ne doesn't work

Manufacturer? Model? Construction year?