what are the value and voltage numbers I get from reading BT_LV thru an ADC pin?
I’m using an ADS1115, i2c module, connected to BT_LV and my Raspi 4 board.
Currently I’m seeing returns from the ADS as e.g. Value=17700 and Voltage=2.21.
The documents say that the value of BT_LV is 1/3 the actual voltage level but, what is it based on?
If I multiply the 2.21 * 3.33 I get a voltage of 7.359.
Is it based on the 8.4V max or 4.2V of each battery?
So, to recap… what is the actual voltage that triggers LO_DT and what is the value I’m getting from the BT_LV pin via analog input?
Thanks for whatever info you can provide.
Wish this information was in the “documentation”.
Kerry
The 1/3 ratio of BT_LV is most likely designed based on the resistor ratio in a voltage divider circuit, with the goal of adapting the high voltage to a safe measurement range and calculating the actual value through software.
The maximum voltage for each cell is 4.2V, so the maximum total voltage for two cells in series is 8.4V. The actual voltage that triggers LO_DT is around 6.4V.
LO_DT is the battery low voltage status pin. Under normal conditions, this pin is low. When a low battery voltage is detected, this pin goes high. The value received at the BT_LV pin is approximately 2.3V.
It only goes high momentarily when a low battery voltage is detected, and it returns to low after the Raspberry Pi is powered off. You can measure the voltage at the LO_DT pin when a low battery voltage is detected.