I know this question might be too broad or too generally worded, but I'll ask it anyway, because I can't find it anywhere else.
Is there any simple way how to convert any old phone (fully functional) to a home-made power-bank/UPS, so that I could use it to power a Pi? For example:
- phone as a charger, battery used separately
- phone + battery used together to power
I don't require whole instructions as I'm not giving a specific model of a phone. ( I'm asking in general). I'm just curious if it is actually possible and if the power supply would be sufficient enough, to at least boot a Pi.
Let's say I have at least Li-Po 900 mAh battery, judging from these calculations a Pi Zero could be powered with this for a while. Then again, it'd be a raw battery, not a power-bank, so... Any ideas?