Voltage Drop on APM Power module

I have introduced some voltage/current issue into my quad but I cant track it down.
Here is the Breakdown of what I have:

1) 30a 4 in 1 ESC SKY III (Timing High)
2) MT4006 Motors
3) (2) 3s 5100 3dr Batteries
4) 14x5.5 CT props
5) 14 gauge wire
6) APM Power module
7) Auqacopters bullfrog frame

The weight all in is 2200 grams.

Here are my calculation from eCalc
http://ecalc.ch/xcoptercalc.php?ecalc&lang=en&cooling=excel...|mt4006-13&gear=1&propeller=t-motor_cf&diameter=14&pitch=5.5&blades=2&project=Bullfrog


The Quad will hover at 50% throttle but the voltage drops very rapidly. It drops to 10.3 in under 10 minutes triggering failsafe. I hooked a monitor up to the battery and spun the motors up to 50% (loaded ). Under load the power module shows 10.3 volts while the battery monitor still shows 11.5. I have swapped out the battery packs twice

I have tried to calibrate the power module via the instructions on the wiki. The voltage matches when with no load hovewever under load the power module voltage Drops off quickly.

a couple of other observations.

1) The current draw from the power module is higher that I would expect 27amp vs 20amps
2) The ESC is really heating up 160+ F, while the motors are at room temperature.
3) eCalc says I should 20 min of flight time. but the power module goes to failsafe after about 10 min.
4) Pluging my batter in right after the flight to the monitor reads 11.9.

I have read other similar threads about unexplained voltage loss but they do not seem to draw any conclusions. (http://ardupilot.com/forum/viewtopic.php?f=49&t=7265)

Should I take it for granted that the power module is bad. aka showing the incorrect voltage, or is there something else going on.

What does a normal voltage drop look like?


Thanks for any help or suggestions.

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I am having a similar issue. I have an f450 that would pull around 20amps at hover with a gimbal/go pro and a 5amp 3s battery. I recently upgraded to the f550 frame and now with 6 motors, the gimbal/go pro, and 5amp 3s battery it pulls around 24amps at hover. The problem is that now the voltage is showing in mission planner below 10 volts and causes a failsafe. I hooked a voltage checker and the battery itself didn't get below 10.5. Any idea what could cause this? Is the voltage reported from the power module to the pixhawk directly? if so than the reported voltage should be almost equal to the voltage from the balance connector?

I'm seeing the same issue here. I've posted some info at rcgroups here: https://www.rcgroups.com/forums/showpost.php?p=37049653&postcou...

Has anyone figured out what the problem is? I'm seeing a 2-3V discrepancy between what the PM is reporting and my multimeter reading under a 10A load.

I've taken a video of it here: https://www.youtube.com/watch?v=SU3ClCOEYv0

Yeah, I had this problem and I couldn't figure it out more than year by ordering many different power modules, but in result problem wasn't with power modules  but with my CHEAP EBAY PIXHAWK!!!

Please don't buy any NoBrand pixhawk from ebay, aliexpress etc. 

Once I bought Brand - "RadioLink" Pixhawk from Banggood I got 90-100% precise readings from any power modules.

Here is link, but it's out of stock right now - http://www.banggood.com/Radiolink-Pixhawk-APM-Flight-Controller-Wit...

It's much more expensive than cheap ebay copy, but much more cheaper than original. I was lucky, I got 35% clearance coupon, when I bought it.

It was my last try buying new pixawk and it was worth that. I was really surprised when I saw precise readings with it.

So answer is that simple, you get what you pay for, buy new pixhawk from trusted Brand or Buy original! :)

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