I just bought the tiny power module to power and measure the current and voltage from an 8S battery.
By putting the available parameters in the guide (https://drotek.gitbook.io/pixhawk-3-pro/main-devices/power-supply/tiny-module). I get a voltage value of 25V while I have 31V. The current value is negative (-280A). I checked that the battery was connected on the right side.
I then tried to adjust with QgroundControl without success.
Do you have a solution for me?
For the moment I’m disappointed, we had an old pixhawk hkpilot32 with its power module that gave me a better accuracy. I hope to have better with a hall effect sensor and for now it’s a failure.
After a few tests, I found a value that I think is just for the current but not for the voltage.
Here are the settings I used:
-BAT_A_A_PER_V : 35.67
-BAT_V_DIV : 9.09
-BAT_V_OFFS_CURR : 0.4
The other parameters are by default.
It’s not perfect but it’s more satisfying. If someone tests with an 8S battery, I’ll be curious to know if they have the same parameters ?
So I found the explanation, it’s very simple. The voltage reading can only be made up to 25.245 V. For a higher value the sensor is saturated. So for my 8S battery, about 30V, the value does not change because the sensor is saturated.
The explanation comes from the fact that it is a simple voltage divider bridge that is equal to 7.65V (value present in the drotek doc). So when I have a value greater than 25.245V, this value divided by 7.65V gives a value greater than 3.3V. That explains the saturation of the analog-to-digital converter!
It would have been nice to put it in the specifications. Only up to 7S for the tiny module !
To solve this problem, simply change the value of a resistor of the voltage divider bridge.