This is a very clever way to make an emergency phone charger from a mint tin. Something like an Altoids can is perfect. Once completed you will have a nice little power bank which can be used to charge your phone among other things.
I can’t vouch for how long it will last, but if you use it a few times in an emergency it would be well worth it. One reader mentioned they made a few adjustments and installed a switch between the battery and the sub charger so they can turn it off and not waste the battery.
Remember, this is an emergency charger. If you only get a partial charge out of it, it did it’s job, and maybe got you out of a bad situation.
The main reason I posted this was to stimulate a little thinking. What other kinds of things could this be used for with a few modifications? Leave your answers in the comment section below.