I’d like to use two xiao nrf52840’s to power a wireless split keyboard. Someone suggested using HAC-006 lion’s to power the boards. (3.7V 525mAh 1.9W). can I simply solder the batteries to the + and - battery spots on the back of the xiao and will the xiao then recharge the batteries if I plug them in to usb? I got a little nervous when I saw a note about batteries/charging/burning out the board.
I’m only using the gpio pins in digital mode to read the keyboard matrix.
The Xiao nRF52840 board does not have built-in battery charging circuitry, so you cannot directly connect the batteries to the + and - battery spots on the back of the board for recharging. Doing so could potentially damage the board or the batteries. You will need a separate battery charging module.
Doesn’t the xiao nrf’s web page says it does battery charging.
Elaborate Power Design: Provide ultra-low power consumption as 5 μA in deep sleep mode while supporting lithium battery charge management
Can anyone else speak to this?
From the Web site,
Features
Versatile Microcontroller: Incorporate the Nordic nRF52840 chip with FPU, operating up to 64 MHz, mounted multiple development ports, supported by Arduino / CircuitPython
Wireless Capabilities: Implement Bluetooth 5.0, BLE functions with onboard antenna, also provide NFC connectivity
Elaborate Power Design: Provide ultra-low power consumption as 5 μA in deep sleep mode while **supporting lithium battery charge management**
Thumb-sized Design: 21 x 17.5mm, Seeed Studio XIAO series classic form-factor, suitable for wearable devices
Perfect for Production: Breadboard-friendly & SMD design, no components on the back
Seeed Studio XIAO nRF52840 has an ultra-low power consumption of only 5 μA in the deep sleep mode, **the embedded BQ25101 chip supports battery charge management** which prolongs its use time. Moreover, Seeed Studio XIAO nRF52840 supports the USB Type-C interface which can supply power and download code. It also has rich On-chip Memory of 1 MB flash and 256 kB RAM, and an Onboard Memory of 2 MB QSPI flash. There are 11 digital i/o that can be used as PWM pins and 6 analog i/o that can be used as ADC pins. It supports UART, IIC, and SPI all three common serial ports. 1 Reset button, 1 3-in-one LED, 1 Charge LED, and 1 Bluetooth antenna are on board, allowing developers to debug their code very easily.
and here is the link to the charge controller[Preformatted text](https://files.seeedstudio.com/wiki/XIAO-BLE/BQ25101.pdf) chip.
HTH
GL 
PJ
No , I believe he is saying that type of battery maybe won’t work in present form?
He can comment , I’ve been using 3.85 LIPO connected without issue for months. Recharging from USB-C power bricks and Charge adapters. No issue’s I monitored it the first time with a USB amp meter and watched as it topped up and didn’t over charge. (pic’s are on here)
HTH
GL
PJ
To power the Xiao board with batteries, you can solder the positive and negative terminals of the batteries to the corresponding battery spots on the back of the Xiao board. Its important to ensure that the batteries you are using are compatible with the board and its charging circuitry. The HAC-006 Li-ion batteries you mentioned have a voltage of 3.7V, which should work well the Xiao board.
When you connect the batteries to the Xiao board, the charging circuitry on the board should handle the charging process when you plug the board into a USB power source. The board should detect the connected batteries and initiate the charging process automatically. Thanks for marking my answer as best.
