ESP32 V3 read battery voltage

#1

How do you read the battery voltage for the new ESP32 V3 boards? Any suggestions are welcome.

1 Like
#2

WiFi_Kit_series/AnalogRead.ino at master · Heltec-Aaron-Lee/WiFi_Kit_series (github.com)

#3

I have seen this code to read analog signals. But which pin is connected to the battery? Pin 1?

#4

Yes, indeed, GPIO1 is ADC pin

#5

Good day

Do you know, how can i detect if the board is powered normal/ with the battery?

Regards

#6

@mechanix your best bet is to do a bit of a guess on the battery voltage: a normal battery never goes above 4.2 or 4.3 volts, so if you read more than that, it’ll likely be due to USB power. On USB, I usually read about 4.8 volts.

I do have a piece of code somewhere that can detect whether the board is connected to a USB host (such as a computer or laptop), but it fails to register if it is connected to e.g. a powerbank or simply a USB wall adapter. So that’s not really useful for this.

#7

Hello and many thanks for your reply!

That is what i am trying to have - a signal, when the power is disconnected. Basically, I want to store some variables in flash memory when the power goes out. I want to power it with onboard 5V pin, but i can also use usb port. So far i found only an idea with simple voltage divider (2 resistors) - to lower voltage under 3V and measure it on a pin. Can you advise?

Regards

#8

The easiest should be the following:

  • always read the battery voltage
  • if the battery voltage < 4.3 Volts, then you are on battery power
  • if the battery voltage > 4.3 Volts, then the battery is charging due to some power source (USB or 5V)

Since the battery voltage pin already has a built-in voltage divider, you shouldn’t require any modifications or additions.

#9

Good day.

I need to save the variables in the exact moment when the power goes off. The voltage at battery goes down, but not that fast. I think measuring this 5V pin can solve my issue.

Thank you for the time and help!