The kettle is cool, but as a thermos it practically doesn't work - the water cools down very quickly inside it, after boiling the temperature outside the kettle reaches 55 degrees. However, you can boil 1 liter of water using 220V in 15 minutes or using 12V in 50 minutes.
I've tried using it with DC12V and also with AC220V, and I'm satisfied. However, with DC12V, since the battery is around 500W, it consumes a bit of power to use as a sub battery. It's better to use it while driving. I tried heating water partially with cold water, and there's a difference in boiling time between 12V and 220V.
At 220v, it takes about 10 minutes to reach a water temperature of 100 degrees. At 12v, it seems to take over 20 minutes. The product is sturdy and good, and the delivery is fast too.