Hello

I pose the question to anyone willing to chip in..what is the biggest factor in extending flight times for a quad? Best/largest battery, decent motors/props, cheap escs? Good battery and Best motors? Best of all?

One of the places I fly I see occasional phantom flyers and this is typically what happens. I start flying, he takes off from his phone, shoots up to couple hundred meters and its no longer in sight. About 8 minutes later my voltage alarm screams at me and tells me to come down which I do gladly. Another 10 minute later I'm sure the phantom lost GPS and drifted to infinity. Another 5 minutes pass and I hear motors and finally see the quad coming down for a landing. He takes battery out and goes again.....

I don't regret any of the time I've spent working on my quad as I have learned alot and know how to handle many different situations but I've often wondered what is the secret sauce that gets you to that type of endurance.

The big thing I noticed from the DJI quad is the 5200 mah battery that costs 100$. I typically fly 3300-4000 mah. I also typically fly the battery down to storage voltage (11.4 V) levels to hopefully extend life of battery. From what i've seen the dji users have no idea the voltage of the battery but are given percent life left. How far are they pushing their batteries?

My next vehicle I'm working on will be around the 1.5-2.0 kg. I'd really like to get to 20-25 minute endurance. Any advice on how to push the endurance please inform me. I typically use HobbyKing for items since they are cheap but maybe this is my downfall. I've never tried any of the top end stuff but if it would bring me to the 20-25 minute level I'd consider it.

Cheers

Steve

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Replies

  • Both the Phantom and Walkera x350 were upgraded doubling flight time. The new ones p2 and x350 pro both went from 2200 to 5200 mAh, but dual bats for the old ones did not do much.
    The other new thing they got was the larger props. And nothing beats their respective original props for flight time. So props are important. And on the x350p ppl are getting 3-4 minutes extra out of eMax motors and simonk esc.
    • Easiest and cheapest thing to do instead of experimenting with real parts is use a modeler.  This one lets you pick real components if you pay for the $1 per month.  Totally worth it!  Saved me hundreds probably instead of real experimentation:

      http://www.ecalc.ch/xcoptercalc.php

      The biggest factors I noticed, in order of bang for your buck:

      1.  Prop size.  The bigger the better.  Number of blades didn't matter much.

      2.  Low KV motors.  Just make sure you can still get ~1.5 to 1 thrust to weight, otherwise you wont fly very far :).

      3.  Weight.  What helped me a ton was pick a system, and start increasing the battery capacity.  Make a chart with battery cost on one axis and flight time as per the calculator on the other.  At some point you start paying HUNDREDS of dollars for 30s more hover time :).

      This calculator was VERY close to my real hover times.  My quad weighs in at ~6.2lbs and I'm getting about 30 min hover time with a 16Ah 4S battery.  

  • Developer

    @agentremnant,

    I completely agree with your list except for point 3. about responsiveness.

    I assume you are talking about motor responsiveness and not how sensitive you have the R/C control sticks, and style of flying. If you did, then forget this. :) Flying smoothly does of course use less energy.

    But motor responsiveness, should be tuned as aggressive as possible without getting into problems with motor sync etc.

    The reason for this is that a multicopter is by design inherently unstable. Meaning that during flight the autopilot is constantly making adjustments to try and find a equilibrium where the copter is standing still at the wanted attitude. And if the motor response is tuned down then the adjustments become larger then necessary. And large adjustment requires more energy rotating the mass of the copter back to the wanted position, then small ones. A tightly tuned system making rapid small adjustment gets you much closer to the wanted equilibrium (and optimal power consumption).

  • We have a 20+ minute flight time on a smaller sized 375mm H-type quad running 4s batteries. We sell this in a kit form and RTF versions depending on what you want.
  • I posted something similar recently. Here you go:

    1. Motor / Propeller Efficiency (watts per gram of thrust) - Further, props must have clean undisturbed air to be most efficient.

    2. Weight - Look at the watts per gram of thrust calculation and you can determine exactly how much time you can free up by removing extra wire, connectors etc...)

    3. Responsiveness (yes, if your UAS is highly response and not smooth it will consume more power just like a teenage jamming the gas a brakes in a car get worse gas mileage than someone smoothly shifting and driving.). This applies to POS HOLD and STABLIZATION modes as well. Over thrusting and having waypoint snapping too tight are factors as well. 

    4. aERODYNAMICS - not a HUGE deal.... unless you are traversing distance vs stationary centric ops.

    5. Unbalanced propellers.

    6. Unlubricated brushless motor bearings.

    7. Nylon props instead of carbon fiber. The flex of the prop reduces efficiency

    8. Grams per mAH. Figure out the best way for you to run batteries. Sometimes 3 smaller batters weigh more than 1 larger one. Sometimes not. 

    9. Peripherals. Don't forget all the electronics on your rig are sucking from the same fuel tank. Its not nearly the amperage that constitutes a minute or two. But we are eeking out as much as possible here. Also, if you dont need it.... gain some weight back. 

    Things I dont know.

    Is it more efficient to thrust late closer to the ground vs gradual descent?

    Ideas, I have been working on a release method where I discard batteries mid flight. Its slightly better than a wash (extra weight from servos), but it isn't definitively worth it. Obviously there are limited use cases (and yes I use those little army men parachutes. 

  • Developer

    Weight. If your copter was weightless it would fly/float for ever..

    The low kv motors, bigger propeller etc. all just means to try and combat the weight preventing your copter from flying.

  • I find that using a lower kv motor with a higher voltage 4s-6s gives you a lot more flight time...i just built a t960 hexa with 4114-320kv motors running a 10000mah battery...17inch props ....depending on wind and weather fully loaded i'll get 30-40 min...just bear bones 45+ min...Higher c rated lipo batteries seem to run longer because if its discharge rate and density but adds a little more weight...it's sometimes hard to find the perfect formula ...companys are now going a lot lower kv motors with10-12 cells & 50k+ mah battery packs, trying to stay up forever..I don't use the cheapest stuff but i won't get the most expensive because most of it is made in china and quality control sometimes is not up to par and not consistant. Hope i answered your questions...Aloha oi..

  • I've been using 10,000 mah 4S batteries in my Quad H2O which is not a light frame (waterproof). The batteries come in a heavy plastic enclosure intended for model cars and boats. I carefully slit the case with a dremel to remove the batteries and then splayed the pack out as 2 + 2 which gave me a long and fairly thin pack that fit into my quad. I reinforced the structure with flat fiberglass slats the length and width of the battery and taped them on with light packing tape. I get 18-19 minutes with this pack.

    I haven't been using them lately because I live half the year in Maui and left them behind. I'm twitchy about shipping lipos anyway, and ones that I've modified seem like they should stay put--outside, in a metal box.

  • There are lots of factors at work so its really hard to just pin it to just one. Yes a bigger battery has more energy in it, but it also has more weight. And it seems to me as you keep increasing the battery size you get diminishing returns until you are actually hurting the flight time of your multirotor.

    One thing that is guaranteed to increase flight time is reducing the weight of your craft. However there generally isn't any excess weight on it to begin with so you have to be creative. Ultra light weight frames exist but they are expensive. And the flight time gains may not be as much as think.

    The best thing you can do is experiment. Try larger batteries, try a lighter frame, try new motors. There is tons of interesting and creative ideas that people have had for extending flight time. You don't have to go all out like they did, but just try to integrate some of their ideas into your design.

    Here is one of my favorites:

    http://diydrones.com/profiles/blogs/my-97minute-06second-record-qua...

    Also this is a good thread to read:

    http://www.rcgroups.com/forums/showthread.php?t=1719368&highlig...

    Also don't be afraid to experiment and research. Asking questions and getting answers is alright, but finding answers or what works for you is way more fun.

  • Low KV motors, (sacrifice agility)
    And low weight
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