25
1500W though a fag lighter plug? Good luck with that
(slrpnk.net)
1500W? At 12V that's 125A - That is fucking dangerous! Most sockets are rated at 20A. Most inverters that are >300W use crocodile clips, or preferably screw-down terminal rings. The cable looks way too thin too. That's a fire waiting to happen....
I have a feeling that the main reason behind the melting is the GPUs drawing way too much power, even at stock speeds.