Battery voltage monitor and AD conversion for XIAO_ESP32C

Products & Technology XIAO
82

the power will not automatily shut off if the voltage drops below 2,7-3,0?

83

I think it stops working when the voltage falls below the minimum operating voltage of ESP32C3, but I don’t think there is a function to turn off the discharge from the battery.

84

WOW… i have not tried the battery pad functions because i didnt want to damage so i just use the XAIO Expansion bases, seems like the onboard chip is worthless

85

According to the circuit diagram and data sheet, ETA6003 used in the expansion board also has no battery protection function.
When the battery voltage drops, the ESP32C3 stops operating, and as a result, the battery current becomes very small, but everything is left to chance and is not controlled.

1 Like
86

Hi there,

So allot can be gained by looking at the threads @msfujino recommends he has done ALL of the research on the power end of things in XIAO, and I would add I use these and never have any issue’s leave the protection up to the battery IMO

battery_with_protection
battery_with_protection2677×1623 444 KB

HTH
GL :slight_smile: Pj :v:

1 Like
87

Thank you all for your responses! I really appreciate the time and expertise you shared in answering my questions.
Thanks again for your support!

2 Likes
88

Hi,

I use a 200 kΩ/200 kΩ voltage divider on BAT → A2 for battery voltage measurement via analogReadMilliVolts(). The readings are correct when the Li-Ion cell is connected.

However, when the battery is removed, the ADC still shows ~4.2 V. Multimeter confirms that the BAT pin remains at ~4.18 V without the cell. A 1 MΩ pulldown at the ADC input does not pull it down. The divider node holds the voltage.

I see posts (e.g., msfujino #83) about battery discharge and minimal op-voltage, but those don’t solve this. The issue is that the onboard charging circuit holds BAT at a constant ~4.2 V when there’s no battery connected.

I want to:

  1. Detect whether a battery is connected.
  2. If connected, measure its actual voltage accurately.

My question:
Is there a recommended method or schematic adjustment to reliably detect battery presence and read its voltage under these conditions? P

89

As long as 5V is supplied from either the USB or the 5V pin, I don’t think it’s possible to distinguish whether the battery is fully charged at 4.2V or if the charging IC is simply outputting 4.2V.