Discussions

I'm having problems with voltage monitoring. 

I'm using ArduPlane v2.7.3 and Mission Planner 1.2.52 mva 1.0.
I have an APM 2.5 and APM 2.5 Power Module.

My 3DR Radio telemetry setup back to Mission Planner says my battery is about 0.3v less than it actually is.  For example, right now Mission Planner says battery is at about 11.57v (bouncing  between 11.52 and 11.63v) but I then unplug and test it with my Fluke voltmeter and it reads 11.87v.  Also, it says it is 99% available when in fact it was at 68% available based on recharging my battery just now.

When I put in a fully charged battery, Mission Planner says I have 12.3 but should say 12.6v.

Is this normal?  Is there a way to calibrate it?

I've read this page a couple times: http://code.google.com/p/ardupilot-mega/wiki/Voltage#APM_2.5:_Using_the_APM_2.5_Power_Module_to_measure_current_and_v

It says two things that confuse me:
1) it says to select "APM2.5 3DR IV from the APM Ver dropdown."  But that option isn't available for me.  I instead selelct "2: APM2.5 - 3DR Power Module."  This probably is no big deal.
2) Typing in the APM Input voltage on the Battery Monitor Configuration screen is apparently not necessary starting with ArduPlane 2.7.1.  I read in the ArduPlane 2.7.1 release notes that "auto-scale analog input based on board voltage. This also removes the INPUT_VOLTAGE parameter, as it is no longer needed."  And if I do try to type something in the APM Input voltage field MP displays a popup window saying "Not Available" with an OK button.

Any feedback welcome.