3V3 pin vs. BAT+ pad on ESP32C6 XIAO

I realize that the BAT+ pad on the XIAO ESP32C6 has extra functionality and allows for charging the battery (and the BAT- pad and the GND pin are connected internally on the XIAO so the BAT- pad is not really needed if using a PCB). The thing is, my project works perfectly with a 3.7 lipo battery connected to the 3V3 pin and GND pin (instead of the BAT pads). And i’m still having trouble connecting my PCB to the BAT pad. So I am wondering, if my project works fine using the 3V3 pin with a 3.7v lipo battery, should I not use this pin? Can I damage the XIAO this way? I’m prototyping what I hope to be a mass produced product, so I need to know if this is OK.

@Seeed_Harrison I’d also appreciate if there is an official Seeed position on this issue. Can I damage my XIAO this way? What is the voltage range I can use on the 3V3 pin? Thanks!

Hi jonesq,

According to “4.2 Recommended Power Supply Characteristics” in the datasheet, the recommended power supply voltage for the ESP32C6 is 3.0 to 3.6 V. If a 3.7V LiPo battery (4.2 V when fully charged) is connected to the 3V3 pin, the ESP32C6 will be damaged.
Also, connecting to the 3V3 pin will not charge the LiPo battery.

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Thanks, but I’m wondering if the XIAO 3V3 pin has some sort of internal LDO voltage regulator, or some other internal resistance, before it gets to the ESP32 chip. The lipo battery (which you are indeed correct that it is 4.2v when fully charged) is working well, so I am scratching my head on this one.

Check the schematic: pin 3V3 is the output of the LDO and is connected to VDD of the ESP32C6.
How do you plan to charge the LiPo battery? Will you use an external charger (circuit)?

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Thank you. Can you give me a link to the schematic? I am using a separate battery charging module as the built-in XIAO charging module didn’t support charging while the circuit is active (at least it didn’t work in my circuit). If the 3V3 is connected directly to the VDD of the ESP32C6 then I am out of luck, although curiously powering the 3V3 pin directly via the lipo battery is working and is very stable. I tried using a separate 3.3V voltage regulator to feed into the 3V3 pin but it didn’t work, the regulator output couldn’t handle the current fluctuations of my system. So ultimately, I either need to find a different dev board (although I do like the wireless on the XIAO, the built in antenna is superior) or find a manufacturable way to connect the PCB to the BAT+ pad.

There is a link to the schematic on the bottom page of the wiki.

I believe that the LiPo battery has low internal impedance and can supply more than the 300mA peak current required by the ESP32C6.

If you use an external regulator, you will need a fairly large capacitor that can supply the 300mA peak current.

edit:
Whether there is a problem with LiPo battery connected to the 3V3 pin and also powered by USB-C should be carefully considered.