# LiPo Battery power monitoring with ESP-12E

I am using 3.7V LiPo battery and ESP-12E in this project. I need to monitor how much charge is there in the battery to help when battery falls below certain level and notify to charge it up again. I've red that 3.7 LiPo batteries maximum voltage goes upto 4.2V. And readable analog input voltage for ESP-12E is 0-1V. I was planning to make a simple voltage divider to convert 4.2V to 1V and provide it to analog input of ESP-12E. Voltage divider resistors - Input Voltage:4.2V Output Voltage:1V R1: 1 Kohm R2: 330 ohm

So as charge in the battery drops the analog input voltage to the ESP-12E drops. But I have a doubt about voltage divider wether to use voltage divider or something else for this project. Because voltage divider will consume power continuously to drain the battery and will cause the circuit inefficient. and I've also red that voltage divider is mostly used in high impedance circuits.

So is simple voltage divider suitable for this circuit or should I use some other DC-DC converter or regulator for converting 4.2V to 1V more efficiently to drain as much less possible power from battery itself to provide it to analog Input of ESP-12E?

• What is the mAh capacity of your Lipo? Jun 19, 2020 at 21:14
• why don't u use higher values for resistors, like 10K & 3.3K. You could also use precision resistor with tolerance of 1% or lower. Jun 19, 2020 at 21:16
• LiPo Battery capacity is 500mAh. Jun 19, 2020 at 21:18
• I would use voltage divider but with a PMOS in series at the battery voltage side. Then control the gate from the uC, pull the gate low only during the battery voltage measurement. That way, if you then for example, measure only once every few minutes, power consumption from the voltage divider is so small it can be ignored. Jun 19, 2020 at 21:25
• I could use higher value resistor but how could lower tolerance help (is 5% not sufficient)? and also will this be better in terms of power consumption than that of any alternative for voltage divider? Jun 19, 2020 at 21:28