* QI compatible wireless charging coil delivering 5v and > [500 mA](https://docs.ai-thinker.com/_media/esp8266/docs/esp-12f_product_specification_en.pdf): For example [this](https://aliexpress.com/item/4001154059743.html), search keywords: "pcba receiver module qi". Alternatively you could repurpose coils advertised to convert non-QI phones to wireless charging, such as [these](https://www.pearl.de/mtrkw-9811-qi-kompatible-receiver-pads.shtml)*.
* **NOTE**: Be aware that these 'converter pads' could contain additional circuitry that condition the output for use with specific mobile phones (the pearl.de ones do). Below is a guide to modify the 'pearl' coils to deliver maximum voltage (5v)constantly, instead of switching to low power, 2.5v output when not enough/too much current is drawn.
### Modding Coils/pads
If you have soldered all components together and your ESP12f won't boot, you might have to modifiy your charging coil+circuit a bit. To make sure it's the coild, measure the output of the coils electronics on the + and - (gnd) terminals. If your multimeter reads ~2.5 volts you need to modify the circuit. (Disclaimer: the exact details on how this circuit works are yet unclear, comparing to a working coil revealed several differences in the electronics, matching them up made the non working coil output the needed 5v).
A hot air reworking station + tweezers will make quick work of that (settings: 1 second on 320deg, modertate airflow). Without hotair you could try a soldering iron or fine wirecutters to simply cut away the chips. The flexible PCB is very fragile though.
With both chips removed, you have to bridge two of the three (now) bare connections of the transitor Q4. I could not find a datasheet on this transitor so please refer to the photo's to see which pins.
