Yeah for this reason I replace the battery of old tablets that I use as control panels, with a DC-DC converter.
Simply removing the battery isn't enough because most tablets refuse to run on usb power alone.
Simply removing the battery isn't enough because most tablets refuse to run on usb power alone.
But I didn't realise that. Perhaps I could use a voltage divider then or simply input 5V. 5V is too high for a battery but most devices accept it there anyway.
You can get rechargeable lithium coin cells. It will just recharge fast.
The cell usually has enough internal resistance and surface area that it can't overheat or violate the charge current limits.
I still wouldn't recommend this approach, simply because the DC/DC converter approach you specified is slightly more power efficient (onboard chargers tend to have poor energy efficiency - many are simple linear regulators from 5v!).
https://old.reddit.com/r/homeassistant/comments/13ovuqn/ive_...
You can use an LM2596 to step down the voltage.
https://www.amazon.es/gp/product/B07PBCYTFW
These adapters seem similar to what's used in that instructibles link. I didn't pick these for any specific reason other than they were available on Amazon. It uses the same LM2596.