I have a Volt/Current sensor connected to the APM 2.5.2 board via the PM port:



And as instructed by the vendor, it's configured as a 3DR power module:



Now I have a discharged 3s Lipo, which is 11v on a volt meter. Then:

1. When connect the APM to a computer via USB cable, and run the Mission Planner. It shows the battery is 11.2-11.4v. I think this is acceptable.

2. When connect the APM to the computer via a Xbee wireless link (The Xbee is on the Telem port on the APM board), the Mission Planner shows it's 13.6v!

3. When connect a minimOSD to the Telem port and read the FPV screen, it is around 13.6v too.

So the USB port sends different figures than the Telem port???

Any idea? Thanks!