I own a laptop but without the battery (since I never used it, I gave it away). Since it is required to have a charged battery on some flights to the US, I was wondering how to bring my laptop to the US. Who should I contact to get an exemption?
There is not an "exemption" you can apply for, all you can do is take your power cord with the laptop and tell them that you only use the computer when plugged in.
TSA officers have the right to ask you to turn on an electronic device to prove it is a functional device. But not every device is checked, nor every flight, it is at the discretion of the TSA officers on duty when you arrive.
My experience is that they will allow you to use a wall outlet (they did for me after one long flight where my work needs exceeded my battery life)