Photonicinduction's 10-second kettle[1] doesn't use a battery, instead it uses his 100A 240V input through a big variac to run at 10kW (440V, 22.7A). This isn't good for the longevity of the kettle he used, sadly.

[1] https://www.youtube.com/watch?v=dDLw1Rx_cAI

At that point one might as well get an instant boiling water tap system.

Joking aside, I use a Zojirushi vacuum kettle that keeps the water at the correct temperature at all times, so I never wait.