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Help with high power consumption.

Con GCon G Sydney AusClub Members Posts: 26

I have built a hexcopter to carry a gopro and I'm finding power consumption to be a bit high causing battery life to be too short. I have a moderate knowledge level of this stuff but wondering if someone could offer some guidance on if its possible to reduce power consumption. Below is a list of the important stuff I have used.
Frame: https://hobbyking.com/en_us/s550-hexcopter-frame-kit-with-integrated-pcb-550mm-black.html
Motors: https://hobbyking.com/en_us/ntm-prop-drive-28-26-1000kv-235w-short-shaft-version.html
Props: Various brand 9X4.7 SF ( I have been experimenting with different brands but all produce about the same results)
AUW: 2.1kg running a 3S 5800 lipo.

Drone flies beautifully, power is just right but I'm not sure if I could lower current draw. Motors/speed controls don't get warm at all. I have tried 10X4.7SF props but power consumption goes up to around 21A and things start to get warm. 10inch is the frame's limit so can't go bigger.

Sitting on the bench with drone armed, all accessories powered up (Gimbal, Gopro, lights, GPS locked on, OSD on, video TX powered up, e.t.c) I am getting around .5a draw which I'm ok with (props not spinning), if I pick up the drone and move it around forcing the gimbal to work harder this will go up slightly but not by enough to worry about (<10% increase). In a stable, altitude hold hover out of ground effect (>2m high) and no wind the drone is drawing around 19A according to the power module and OSD (I suspect the actual current draw is higher and the power module is incorrect as I'm only getting around 10 mins flight time). I'm going to test this with a proper power meter and compare with the power module.

Question is, is this the best I'm going to get with this sort of weight (don't really have an option to reduce weight as everything on the drone I'm happy with and want to keep as is). Or with different motor/prop combination will I be able to reduce current draw. I'm a bit reluctant to try different motors unless I know they are going to be an imporvement as they are not cheap, esp when I'm buying 6 of them. I'm thinking of trying 8inch SF props to see what that gives me but Ihave a feeling the power of the drone will suffer. I'm hoping someone with a more thorough knowledge of motor/prop combinations might be able to chime in with some advice.

Thoughts?

Comments

  • HobbyKing_SupportHobbyKing_Support HobbyKing Support Posts: 388 ✭✭

    It sounds like you've set things up quite well though those motors should only really pull up to about
    ~15A-18A according to specs so 21A is a little on the high side. Which ESCs are you using?

    The first thing I would examine is your lipo... how high is the C rating? A higher C rating (60+) may help things run more efficiently. In reality a 10 min flight time sounds about right for that much weight and only one 5800mAh lipo. 8" SF props probably would lessen amp draw but you're right that power would also suffer a bit. It's always a tradeoff or compromise between power and efficiency. If you can run two lipos in parallel that would effectively double your flight time with only a minor penalty in weight.

    This lipo may be a good choice:
    https://hobbyking.com/en_us/zippy-compact-5800mah-3s-60c-lipo-pack.html

    You may also want to try 4S lipos.

    Other user's comment:

    "X-666 quadcopter (heavy build with FPV gear and lightshow)
    10x3.8 APC prop
    4s3300 nanotech 65-130C
    About 10 minutes of airtime...still fine tuning prop selection"

    Let us know how the test with the power meter goes.

  • Hobbyking_IanHobbyking_Ian Club Members Posts: 117 mod

    Amps are pulled not pushed so if you want less current draw fit a lower pitch prop. Try a 10x3.8

    In terms of battery, try a multistar 10c You might find you can have a 5000mah pack for the same weight so your just getting more flight time and they are cheaper

  • Con GCon G Sydney AusClub Members Posts: 26

    Thank you for the replies. I have been having some other related trouble with the drone so have been unable to work on this problem. I hooked up a watt meter and found the readings I was getting through the OSD to be way off (as I suspected). Prearmed I was actually drawing about 900ma (osd was reporting 400-500ma) confirmed with a watt meter and a multimeter. With throttle at 50% is was drawing 24a (OSD reporting around 19A). I have played around with current per volt and other battery settings in the firmware but can't seem to get a consistent close to accurate reading across the various running conditions (i.e I can get it report correctly at 50% throttle but its then way off at idle or higher throttle settings and vice versa if I set it up for idle power consumption). I tried changing over to adrucopter firmware but that's when I started having other problems. Things like motors not spinning up when armed, very gittery flight. I went back to PX4 firmware but the problems remained. I have been working on this over the last few days and am finally starting to get it fixed so back to working on the power consumption.

    I like the idea of a lower C rated battery which will hopefully be significantly lighter so I will look at some batteries around the 10C 5000mah range which should be able to supply 50a without breaking a sweat and be plenty for my setup. I'll report back with my findings.

    Just to confirm the amp figures I'm using are the total draw of the copter including all motors and accessories, not individual motors.

    The speed controls I am using are these https://hobbyking.com/en_us/afro-20a-multi-rotor-esc-simonk-firmware.html

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