Just finished the test with the EPIC. I'm slightly confused with my results... my flight time was just over 6 minutes. However the copter is only reporting using 11,000mAh out of the 20,000 total available? These batteries are pretty new still and have been taken care of. Also there really isn't that big of a load on them. Is there something up with the voltage reporting that the copter is giving me back? Here is the log file: Flight date: 9/10/2014 1:33:55 PM Flight time: 1:33:55 PM.4 - 1:40:04 PM.6 Duration : 369 secs, 00:06:09 Batt. time : 368 secs, 00:06:08 Start Location : +33.6054769 / -111.8632682 @446.5m Elevation(GPS) : -7.106 3.3 14.631 m (min/avg/max) GPS alt. (raw) : 439.725 449 461.462 m Altitude(Barom.): -0.15 7.42 16.65 m Vertical speed : -1.88 -0.04 2.62 m/s Max speed : 17.6 km/h Max target dist.: 0 m Max distance/LOS: 31.5 m / 32.2 m Sats : 7 6 8 Voltage : min. 21.7, max. 24.6 V Current : 0.5 115 161.8 A Wattage : 11 2617 3656.68 W Capacity: 11752 mAh Motor1: 1.7 15.3 25.1 A Temp: 39 52 59 °C Motor2: 1.2 13.9 23.4 A Temp: 40 55 61 °C Motor3: 1.2 12.7 20.9 A Temp: 37 53 59 °C Motor4: 1.4 12.3 18.5 A Temp: 38 53 59 °C Motor5: 1.9 14.2 23.4 A Temp: 37 58 66 °C Motor6: 1.7 12.8 23.4 A Temp: 37 58 68 °C Motor7: 0.2 17.2 25.3 A Temp: 37 61 69 °C Motor8: 0.0 16.8 25.3 A Temp: 37 59 69 °C Magnet Field: 84 93 105 % (ok) Magnet Inclination: 52 57 72 deg Errors / warnings: FC-Flag "LowBat" (5) occured 329 times! As you can see the copter is only seeing 24.6V as max voltage even though the battery was charged to 25.1V. I'm only pulling an average of 115amps which equates to 57.5 amps from each battery. These batteries are 10,000mAh and rated for 25c so effectively I should have 500amps max without any issue so why would i have such a huge voltage drop when I'm only pulling 57.5amps? Thoughts? Next time I will put a voltage alarm on one of the batteries and see if that goes off at the same time as I get the low voltage alarm on my Tx (It's set to go off at 22.2V or 3.7V per cell). I'll post the pictures and video soon. Josh
The MK "low voltage" alarm is a little misleading. It fires at whatever level you set. In your case with the Tattu LiPos (the best out there IMHO), you can go closer to 21.0V before being concerned. I have regularly seen 5-8 minutes of flight time between 22V and 21V, with plenty of headroom left when I land. But you should inch that number down carefully, as you're flying pretty heavy compared to what I do. Bottom line: you should set up your low voltage alarm to your own taste.
Wow I didn't realize you could go that low on them. Good to know. I'll do another hover test with them and will put a lipo alarm on for 3.5 and see what it does.
I'd go down by 0.1V each charge cycle and make sure the batteries are happy. Ever since I've set my low voltage alarm to 21V I've yet to hit it. I just listen to the Grapuner and generally head back at around 21.5V...or at least think seriously about it.
BTW, it also looks from your compass values you could benefit from an external compass. Do you have one?
Raw, no post stabilization... and no tuning on the gimbal... also was out of balance and in the Majestic mode. Overall still WAY better than anything else i've ever gotten on our old gimbal. With proper balance and tuning it would be perfect.
Josh: All the things that you're observing point to the voltage and current sensors on the Herk board not giving accurate data. Are there any calibrations that you have to do (rather like the BL-Ctrl v3 calibrations)? Andy
Andy, as far as I know it's not possible to calibrate. Josh, when you charge these batteries, how much capacity did you able to put back on to the battery? This way, you can be sure if the amps consumption data is correct or not.
Josh When I started switching over to the 4120's I noticed that the voltage dropped a bit faster but the amount of energy spent was about the same. At first I was seeing 8 minutes of flight time when I first installed the 4120's. First thing I did was calibrate the BL's to make sure the actual power consumed was accurate. I performed a flight with a pair of batteries, and after the flight charge each battery in solo mode. After each battery was charged I wrote down the total power that the chargers put back into the batteries. I then added both of these together and saw how close the actual GPX data was. It was quite off, the actual power spent was much lower than what was reported. I would then adjust the factory set number from 64 to whatever I needed to accordingly. As it turned out I needed to change this number up to 72. Now the actual GPX data was actually accurate as to how much energy the batteries were actually discharging in flight. I then monitored the telemetry with voltage and power spent. I was finding that when it reached 21.6 I was around the 12,000 MAH mark of power actually spent with 2 10,000 MAH batteries onboard. I would reach this point about 8-9 minutes inflight. I then found I was able to get another 3 minutes of flight time until the batteries actually spent 16,000. At this point voltage was about 21.2. I actually did a test where I got the copter in flight about the 13 minute mark and actually let it fly very close to the ground. I wanted to see if the data was really working so I didn't land the copter until 19,500 mark. I was able to get 15.5 minutes with it spending 19,500. I then charged both batteries in solo mode and combined they put 19,350 mah back into both batteries. So now I am setting the low voltage alarm level at 21.4 but I'm not actually trying to land until I get to the 16,000 mark. So I'm using the power spent number more as a true indication of how much time I really have left. Since you are running the Hercules board you need to see if there's a way to calibrate each ESC "IF" your actual number is off. You might want to try this and see if you get similar results. Hope this helps.
Thoughts on the batteries now that you have flown with them more Josh? I see your running 2 6s 10,000. I am going to switch from freefly batteries to something else and looking at tattu and either their 6s 10,000 or 6s 16,000
Hey Everyone, Thought I would give another update after flying the copter a lot lately (about 55-60 flights now in the last 2 weeks). First thing, IT FLIES BEAUTIFULLY!!! I mean best flying machine I've ever flown. It is super stable, even in strong winds (did a test flight in gusty 20+mph winds with our Canon 1DC on there for weight and it just moved around the sky a bit. No shaking, vibrating, ect. Very predictable and I still felt safe flying it. I will never need to worry about the copter overheating again. We did a job about 2 1/2 weeks ago flying an EPIC with heavy Zeiss cinema glass and it was around 109-111*F outside for ambient temps with no wind. Highest temp I saw after looking at the log files was about 55-60*C. Motors were warm but not hot. I have noticed, and after talking to a few other people, that the KDE motors tend to run warmer then other motors. They are the same temperature no matter what my payload is, from nothing to EPIC. There is only a few degree difference. The only problem I have been having, and I'm not the only one, is my AH only works when hovering... it holds perfectly in a hover but as soon as I fly forward or backward it starts to drop then if I go back to hover it climbs to where it should be. Another guy who is having this issue has been talking with Holger to try and figure out what is causing it. We have tried both the 0 for throttle setpoint and 127. Both behave the same. I never fly with AH so it isn't really an issue for me but it would be nice to have I guess. Oh and this thing is FAST! We flew it faster than I've ever flown one before and it still had more left in it! Even at the higher speeds it was still perfectly stable. The climb rate on it is insane as well. I've only done a full throttle climb once and it was scary how fast it climbed. Went from 12ft to 81ft in 1.2 seconds! Last thing is flight times. With our 1DC we get around 11 minutes. Thats landing when batteries are reading 21.3V. With an EPIC we get between 8-10 minutes depending on how it's setup. Josh