Battery Power observation

No issues here, just an interesting environmental observation.

I have a few cubecell’s under test running only on battery.
One has a 700mAh LiPo and was set up a week ago transmitting every 10 minutes to TTN. I also left the LED running so i could see the transmission cycles.
Start voltage on the battery was 4.18V, the USB was pulled and the unit’s power cycled.
Last night the voltage was sitting at 3.87V and that is after a week of running however this morning the voltage has risen to 3.91V.

I suspect this is because last night the temperature was about 20 degrees C and this morning it had risen to 23deg C. I may make up a peltier to stick on the battery and decrease the temperature to confirm my suspicions but find it rather interesting.

One of the other units is running 2X 2400mAh 18650’s and the voltage seems to be rock solid at 4.14v

temperature is essential for LiPo or LiIon batteries.
just a few degree more are less can change the usable capacity.

I knew it did but did not realize they were so sensitive to change. being able to see the change over only a couple of degrees is prety interesting.

One reason is the temperature.

another reason is may be a problem with the battery itself or inaccurate ADC measurements.