[herschel113]

And most likely always hot.

The nuclear process can most likely not be controlled, and will just provide energy the whole day long. A small sidecar battery may hold charge for peak usage, but still the nuclear battery have to churn atoms all the time to provide the mean power. And the conversion process usually is not very efficient either (but I don't see numbers for this particular device).

[kwhitefoot]

> will just provide energy the whole day long.

Dimension it for just a little more than the average consumption and use a super capacitor or battery to soak up the excess when the phone is idle. I imagine one would need the battery anyway to cope with short term high demand such as photography.

[jvanderbot]

Once you fill your storage you cup runs over. Now you need to radiate something. Heat, radio, light, whatever. You could always run a crypto mine when battery is full and phone is idle, but yeah youre heating your pocket regardless.