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=excellent&rotornumber=4&config=flat&frame=550&tiltlimit=90&weight=2200&calc=auw&elevation=500&airtemp=25&qnh=1013&batteries=0&battcap=5100&battri=.0068&battv=3.7&battccont=20&battcmax=30&battweight=86&chargestate=6&s=3&p=2&esc=max_30a&motor=tiger_motor&type=46|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.
Replies
Current draw should be 21 A with a good motor so with 10200 mAh 3S you should fly 28 minutes .
With 27A and 10200 mAh 3S you should fly 22 minutes.
So apparently your batteries are almost dead .
Hi Eric. If your ESCs are getting hot then the first thing I would do is lower the timing to Med. Low or even Low (higher timing rates normally work better with high kv motors.)
Regarding voltage loss and flight times, are you starting with fully charged batteries - i.e. is each cell is at a full 4.2V?
In mission planner, is the displayed voltage exactly the same as when you measure the battery (connected) with a reliable voltage meter?
What voltage is your failsafe set to? If your 3S flight battery measures 11.9V on landing (after a triggering an alarm/failsafe) then it's set to trigger way too early.
Same problem, tried many power modules.. still experiencing this problem. Hope someone could help. I have Micro APM from HobbyKing and Pixhawk both using different power modules, both of them have same problem described here. Can't figure out WHY!!!!...
Hi Eric,
I know it's been awhile since this post, but I've just started experiencing the same issue with my Hexacopter. I think I've been having the problem all along, but I've just added a FrSky Voltage Sensor that give me real-time readings while in the air. I've calibrated the Pixhawk power meter but it would always read about 1-1.5V below what the FrSky sensor was reporting at the balance cable, so I just started going by Lowest Cell Voltage from the FrSky sensor...BIG MISTAKE!
I was flying the other day and my Lowest Cell Voltage reported to my Taranis read 3.6V, so I assumed the voltage at the flight controller was about 10.8V (3.6V x 3s) which should have a little bit of flight time left, or at least enough to safely bring it back for a landing. Unfortunately, I looked up to see my copter slowly dropping out of the sky and crashing (fortunately a slow descent from only about 15 feet and almost no damage). My only conclusion is that the power module and/or power distribution board really are eating up more than 1V between the battery and the ESCs/Motors. Very frustrating!
I've ordered a power module/BEC kit from Christian at http://www.mauch-electronic.com/ which I'm hoping will address some of the resistance and calibration accuracy issues.
-
1
-
2
of 2 Next