I'm prototyping a ultra low power wireless sensor.
To consume less I run a arduino mini pro at 1.8V at 8MHz with sleep 99% of time.
The power comes from a LIR2032 coin and the 1.8V is generated from a LDO regulator HT7318. I use the regulator cause my NRF24L01 will not support such as 4V voltage and cause an atmega328p consumes less with a lower voltage
I want the consumption be as low as possible (nA/pA if possible)
But to preserve battery life I have to know when voltage goes down.
I'm interested in the Nick scheme:
Measure Lithium ion battery voltage (thus remaining capacity)
But I got some trouble :
-A direct battery measurement is fully stable but drain battery.
-With Nick scheme it doesn't drain battery but I like to reduce the measurement time needed cause of the capacitor C14. (I added a capacitor to the arduino output to cut off the measurement a short time after switching)
-If I remove the capacitor from Nick scheme, the measurement is absolutely not stable, but I don't understand why ?
I read there are some all integrated solutions like LTC4150, are they better or worse considering ultra-low consumption?
Other links I found:
Low power battery voltage monitor
Zero or low-current voltage divider for switch identification
Which MOSFET to use for battery voltage measurement?
Reducing Voltage Divider Load to Extend Battery Life
Topic: Battery monitor/sensing ratio calculation on MotionMote/WeatherShield
Power saving techniques for microprocessors
Arduino Pro Mini: Power consumption
Sorry for my poor English :)