Can PyCubed v05 safely charge a 1S (4.2 V) Li-ion battery via USB without modifications?

[TheHomieCMBK]

I’m using PyCubed v05 and I have a single-cell Li-ion battery (1S, 4.2 V). I’m trying to understand the existing USB charging behavior and whether it is safe (or possible) to charge a 1S cell using the board without modifying hardware, software, or firmware.

Here’s what I found / what I’d like to confirm:

1. The documentation states the BQ25883 is configured by default for 8.4 V (i.e. for a 2S pack).
2. he included bq25883.py driver doesn’t seem to expose a way to change the target voltage (VBATREG) to 4.2 V.
3. Therefore, if I connect a 1S battery without modifications, the charger might overcharge it to 8.4 V, which is unsafe.

My questions are:

• Is it correct that PyCubed v05 cannot charge a 1S Li-ion battery out-of-the-box (i.e. without firmware / software / hardware changes)?
• If that is the case, what modifications (software, firmware, or hardware) are the recommended approach to enable safe USB charging for a 1S battery on PyCubed?

Thanks in advance — I want to make sure I don’t damage anything or risk safety with overcharging.

[pederhc]

I’m also curious to hear the answer to this!

[polygnomial]

Yes, it is correct that the PyCubed cannot charge a 1S Li-Ion pack out of the box without modifications. The best option is probably just to use a 2S battery pack. You can probably run the microcontroller off of a 1S pack, but you will need to select new output resistors for the solar charger circuit (if you intend to charge over USB), you may have trouble running the radio at full power, and there may be other circuits you will have trouble with.

The BQ25883 charger is designed for 2S lithium-ion battery configuration. If you absolutely need to USB charge a 1S pack using a PyCubed board, you will need to select a new USB charger, design and layout a new circuit, and then write an appropriate software driver. You don't strictly need to charge your battery pack over USB, you can also charge it with a power supply or dedicated lithium ion battery charger.