some help with the power module please

Hi,

Can some one please help me with setting up the power module calibration. I have completed all the steps listed in the wiki and configured both volts and current using OTHER sensor as shown in the youtube video.

First a little about the way I have set things up. I am not using the power module connector as I have a dedciated Castle creations BEC powering the input rails at 5V with jp1 removed. I have no servos in my setup. I use a haiyin 35C 5000 mAH 3S lipo but and after 6 minutes I land with just 7% battery left as indicated by a watt meter.copter is about 2kg and im running 850kv motors with a gemfan 10.45 slowfly. I have soldered 3 wires to the points I, V and GND on the power module board and connected to pins A2 and A3. Mission planner is also configured to to read A2 and A3. The Amp and volt readings under load are as close as I can get them when compared to a wattmeter.

Voltage divider is manually set at 10.5 and current per amp is set at 10.65. My problem is that after a 6 minute flight mission planner shows 3900 mah used however when charging im putting back 4600 mah. My low voltage LAND is set at 10.5. Despite that my batteries come down nearlt completely drained which means in an emergency I have no power left and its spoiling the lipos. 

The mission planner battery remaining percentage matches well with a wattmeter after a 6 min flight. Both show 7% left. The voltage on the mission planner under 60% load is marginally lower by roughly 0.2v than what the wattmeter shows. The aps drawn on the mission planner and wattmeter under 60% load is as close as can be...

Can someone please help to set the powermodule up correctly and come to the correct flight timer and LAND voltage.

Thank you.

Arshish

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  • I really need some advice here please... I think I am just stabbing in the dark. Can someone please shed some light on the following.

    1. While setting the battery  moniter Amps, if I set the amps per volt parameter such that the apms match a wattmeter at about 40% load then the total amps consumed after a flight is much less than what the charger puts back in. (Mission planner shows 3600 consumed but charger puts 4500 back). Due to this I have increased the Amps per volt such that mission planner shows what the charger is putting back in. My amps per volt is now 11.5. However this now means that the apms drawn indicated during flight is about 3 amps more than what a wattmeter shows. Why is this happening and is the approach I have taken correct?

    2. I have my timer set for 8.5 minutes after which I land. I then have a low battery RTL set for 10.65V which kicks in at about 9 minutes. (However while looking at telemetry data while flying the volts drop to lower than 10.65v for over 15 seconds before the rtl is triggerd. Is this normal and is 10.65 an appropriate low battey value?

    Thank you.

    Arshish

  • Ive made some progress and I think I may just have it sorted. My batter has also started performing better. Perhaps it was new and needed a few cycles.

    Rather than tune the amps for a particular throttle setting to compare with a power analyser, I tuned the amps per volt parameter such that the Mission planner shows the exact capacity used as is being put back into the battery on a subsequent charge.This has left me with the following settngs for a 5000mAh 3S 35C Lipo.

    Timer 1 - 8.5 Minutes - I should start to manually land now

    Timer 2 - 9.5 Minutes - This is when the battery hits 10.84V and the RTL failsafe kicks in. 

    I know from trial an error that I can fly for 10.5 minutes and land with 6% left based on the watt meter. I know this will spoil the batteries and this is just to low.

    So, when RTL kicks in (Timer 2) it will have 1 full minute for it to land safely.  If I make sure I manually land after Timer 2 and before Timer 3 I should be safe.

    The only issue I have noticed is that if I use RTL manually on a switch and while landing if the failsafe RTL kicks in it will unnecessairly prolong the landing taking me very close to the battery unusable voltage again.

  • Upon testing a little more I noticed that the apm current draw does not match the wattmeter current draw in a linear manner. As in if I get the two to match at 50% throttle, they are off at 100% throttle and vice versa. I have also noticed a similar issue with voltage calibration. I can get it to match exactly at a particular load, but it does not remain linear.

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