ESP8266 Community Forum

- Fri Jan 16, 2015 9:52 pm #7480 With a wire tacked to pin 6 of my ESP-01 board I am getting very consistent readings for 0 to 1.0V as 0 to 1024 using adc.read(0)

Now I will add a resistor divider and use it to shut down when the LiPo battery drops to 2.7 volts.

Just what I needed!

Peter

ESP8266 for dummies, LuaLoader and project updates: http://benlo.com/esp8266

- Sat Jan 17, 2015 5:22 am #7494 I was planning to use exactly that sort of thing to monitor battery voltages also!

2.7V sounds a bit low for cut-off for LiPo cells, I would cut off at 3V at absolute minimum - 3.2V is used by batteries with their own built in charge management chips. So for maximum battery life I would play safe and use 3.2V - the only case for going lower is in a quadcopter or something where you need to get back to earth and it is better to damage the batteries than cut-off power!!

- Sat Jan 17, 2015 8:50 am #7503

I was planning to use exactly that sort of thing to monitor battery voltages also!

2.7V sounds a bit low for cut-off for LiPo cells, I would cut off at 3V at absolute minimum - 3.2V is used by batteries with their own built in charge management chips. So for maximum battery life I would play safe and use 3.2V - the only case for going lower is in a quadcopter or something where you need to get back to earth and it is better to damage the batteries than cut-off power!!

Thanks!

I was going to look up the right value later. 2.7V was stuck in my head, probably from some ancient spec I read that may or may not have been applicable for the batteries I will actually use.

In fact, I know that some devices shut down at around 3.6V, when there is still residual leakage current, so there is lots of time to notice before damage occurs to the battery when it is left in the device. 4.2 to 3.7 leaves lots of room and simplifies the regulator choice, too...

ESP8266 for dummies, LuaLoader and project updates: http://benlo.com/esp8266

- Sat Jan 17, 2015 11:52 am #7515 I connected my lab supply directly to the adc pin and it worked.
That means something is wrong with my voltage divider, even though my voltmeter shows the correct values.