Voltage measurements always wrong

I am using a APM 2.8 and 3dr clone power module.
My voltage readings on MP are always wrong. I have calibrated the voltage monitor multiple times but it always shows a very high voltage…and therefore no low battery alarm.
I sent the voltage monitor, ran the motors at half throttle until 9.3v and no alarm (set for 10.2v). The monitor still showed about 12v.
Also interesting that when I am only connected to USB…no battery…that MP still shows about 12v and current drain while just sitting on the table.

Maybe your clone 3DR Power Module is not functioning like you think it is?

Yes, sounds like a bad clone, this is not normally an issue people ask about.

Is it normal to see a battery voltage displayed on MP when its only plugged in to USB…no battery connected ?

As far as the power module goes…what voltage should I get on the pins to the APM?
I measured them all and don’t get the battery voltage on any of them, so I’m not sure how the APM knows what to display.

Like members have pointed out, your clone 3DR Power Module may not function the way a genuine 3DR Power Module does so it may be incompatible with Mission Planner.

I can accept that maybe the module is defective but there has to be a way to test it. It came with the APM so I’m sure it’s compatible.
I’ll just keep googling it I guess.

the power module have really 4 signals, +5V , GND , current and voltage - on the original one there are clearly marked labels and test-pads.
The 6-pin DF13 connector just uses two wires for 5V and GND.

To test - you would check the voltage pin, that similar to the current pin, should show a lower voltage, proportional to input voltage.
if you feed it 16v , maybe you should measure 1.8volt , if you then apply 8v, you would expect to see 0.9v from the power module.
(I am not sure about the real divider, but you get the point )

I appreciate the reply.
I selected the APM 2.5+ and 3DR module, selected voltage only and it seems to be fine (better).
It’s within .2v most of the time.

Thanks again.