I think you mean when the battery is flat. The thing is, my headphones have never been flat, but when I wanted to use them with a cable, I had to switch them on, so I assume that the pleasure is over when the battery is flat.
If the TV has Bluetooth, you can listen without a cable. Otherwise, you can listen with the supplied headphone connection cable, which can be connected to the headphones, as with normal headphones. However, at approx. 125 cm, this is much too short for this purpose. Extension cables are available here:
https://www.digitec.ch/de/s1/product/inakustik-premium-35mm-stereo-klinken-verlaengerungskabel-5m-premium-35mm-klinke-audio-kabel-2582594.
By the way, I think the sound is great. If you know Bowers & Wilkins from Volvo, you won't be disappointed.
@Bender69: Yes, the microphone on the PX7 is probably the only weak point of the headphones. Unfortunately, it is not very suitable for making phone calls. The person on the other end of the line only understands you in quiet surroundings, and even then he has to listen carefully. If you try to talk on the phone in a noisy environment (e.g. at a train station or in a restaurant), it becomes much more difficult. In my experience, people could hardly understand me.
I am very satisfied with both the PX5 and the PX7, even after a long time. But with a person with such a confused writing style, I'm not surprised if something doesn't work.