Hi,
I am working on a project based on the Nano 33 IOT. The goal is to make a wearable device that can be used on the go, to measure health parameters of the person wearing it. Since it is a portable device, I have to use a battery and have decided to use a step up/boost converter to make sure the ~3.7 V (LiPo) be converted to 5V in order to power up the Arduino (Vin). Simple.
The problem, however, is that I want to also charge this battery using the USB port that is already on the Nano. I figured I can solder the jumpers on the bottom of the board to get the 5V output on pin 12, this will then be connected to a charge IC to make sure the battery is charged accordingly (4.2V). I am planning to include an on/off switch for ease of use.
The question I have however is this: What happens to the battery when the circuit is closed (switch is on) and the VUSB is connected? Will the output of the battery (5V through the reg) be added to the 5V that is coming in through the USB? If so, how do I avoid that? The Arduino can handle 10V, but I do not think that will be wise (for efficiency reason).