I actually looked into this for making coffee while camping. How hard would it be to boil water with a portable battery pack that contains a few 18650 cells? Re

I actually looked into this for making coffee while camping. How hard would it be to boil water with a portable battery pack that contains a few 18650 cells? Regardless of the fact that USB-C at 240W is not really enough, could you do it on batteries? Not very well. It takes a shitload of energy to boil a cup of water. About 0.5MJ for 8 ounces raised from 20C to 100C. My portable battery pack holds about 100Wh of energy. That's 360,000J. So that battery pack has enough energy to boil one cup of water and not quite a second one. And that assumes 100% efficiency. I realize that we're talking about two different things: wall outlets vs. batteries, but boiling water is hard.