Hi,
I purchased PIxhawk 2.1 and it came with its own Power Module (power brick). I assembled and configured a quadcopter. When I connected the battery that is fully charged everything works fine. However, if the battery is not fully charged (voltage slightly off) I get the Low Battery beeping.
It narrowed down the problem to the Power Module. Apparently, it reads voltage about 2 V below of the actual battery voltage. I even disconnected all components from Pixhawk and just left connected a buzzer, a safety switch and the battery through PM, but the problem with the low battery is not going away.
I'm using QGroundControl (on Mac). When I connect a USB cable and the battery, the PM reads 10.55V in QGC, for the fully charged 3S battery, which actually has 12.53V as tested with the voltmeter. At this voltage, I get a Low Battery warning from QGC speaking, but no buzzer.
When the actual battery voltage drops a bit to 12.45V, I get a buzzer beeping and QGC shows only 13% of the battery at 10.46V.
So, Pixhawk's Power Module seems to lose about 2 V from the actual battery's voltage. Keep in mind that there is really no load on the system and ESCs are not even connected - everything is at rest. Did I get a faulty PM with my purchase or did I do something wrong with PM's calibration?
I searched google for straight 2 days but can't find the answer. I would understand if PM loses some 0.2/0.3 V, but not the full 2V. Something seems oddly wrong here.
I'm using 3S 5000mAh 52C battery.
Pixhawk is fully configured with QGC and has the following parameters:
Number of cells: 3S
Full Voltage: 4.05V
Empty Voltage: 3.40V
Voltage divider: 10.17793941
Amps per volt: 15.39103031
Please help!
Replies
Anyt,
Thanks for pointing me in the right direction to look into Voltage Divider value. After I carefully read the instructions I realized that in order to perform the battery calibration the actual battery must be plugged in. My rookie mistake! Once I performed the calibration with plugged in battery the number jumped to 12.23234653, which made QGC to correctly displayed battery at 100%.
Thanks again for your time.
Hi Anyt,
I'm sure the battery is fine, I have 2 of them and the behavior is the same. As I mentioned, I did test the battery with the voltmeter and the voltage is fine about 12.53 when fully charged. I'm a bit puzzled on how to troubleshoot the divider values. I tried your link, but not sure what to put for both resistors. I tried QGroundControl calibration, but the only parameter it asked for is the voltmeter measured battery voltage, I entered 12.53 and got the result as in the snapshot 10.1779.
Since I never did this type of calibration, do you have any advise on the values I can use for my battery? Want to make sure I don't damage anything.
Might be there is a problem with your battery. I refer you to test the battery first of all. You can test the actual voltages by loading test using a multimeter. To do this connect the multimeter probes with 100 ohms resistor and then measure the voltages of the battery. This will tell actual voltages that are left. Once all setup troubleshoot the divider values. Even if the problem lasts please refer to this manual of Pixhawk.