What's The Smallest FPV Drone 6s Batteries Make Sense On? Should I Put 6s On 2.5"? - FPV Questions
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- čas přidán 9. 09. 2024
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Fun fact, magnets losing their effectiveness under heat is how those cheap $10 rice cookers work.
Once all the water is gone, the heat radiates down into a magnet until the magnet under the bowl "fails". The switch flips from cook to warm.
Hmm. Didn’t know that. So that’s what that little disc under the rice bowl in the rice cooker is.
Someone watches technology connections I see
@@joshuajhoyt YES!
Bardwell has explained it theoretically, assuming you have the batteries. In practice, however, it ultimately depends on the availability of the batteries (unless you make them yourself). And the simple fact is that the smallest 6S battery is 1050 mAh (for me my main market). And that limits how small the drone can be for that battery. And in my opinion, in practice, 6S only makes sense with a 5 inch medium weight. At 5 inches ultralight and under 5 inches 6S makes no sense in my opinion (except for 3-4 inch cinewhoops maybe).
you can get 300mah, 450, 550 mah 6s batteries which are extremely fun on 3 and 4inch quads
Great answer. Very interesting. I just built a 3.5" freestyle quad, went with 4s, but wondered about 6s when I was picking motors.
get some 2105.5-2600kv, its a blast with 6s 1300mah,. u sould try it
Theres a couple of points I disagree with here, but they are pretty minimal.
The first one is there are functional limitations on how you can wind a motor that mean there's a limited Kv range you can achieve with a given stator size and magnet combination. In a lot of cases that is the functional reason you end up changing voltages as motor sizes increase even before you run into the power delivery limits of the batteries. Now our 5" drones sit in an interesting space where we can achieve a decent range of Kv pretty effectively, so that's not really a limiting factor for a lot of what were doing, but for instance you can't functionally make a 0702 motor low enough Kv to be useful on higher voltages due to not being able to fit enough turns on the windings with sufficient gauge wire. Same is true in the opposite direction on larger motkrs. At sone point you are at only one or two turns per armature on the stator to achieve the Kv you want.
I also would point out there are a lot of other factors like switching losses and relationship between duty cycle and efficiency of the motor that matter a lot in where optimum voltage and Kv will sit for a given application. Moving the throttle point that is the most used into a more effective band for the motor is a key part of the discussion, and often that is achieved by lower voltages, not higher. It depends on the specific application of course.
My main point woild be that the real point at which you want to go up in voltage is when you exceed the power delivery requirements of the lower voltage in terms of how many watt hours of battery you can carry and how high you can push the Kv.
To that end, I don't actually think 6S makes sense until you get above 2000kv or so. If you actually look at the details of the setup, most folks are running 6S 1300mAh batteries. Those are roughly watt-hour equivalent to 4S 2000mAh, and a 4S battery of that size can pretty easily handle the load of motors up to 2800-2900kv without running into limitations. That's Kv equivalent to 1950kv on 6S at the top end, so unless you're pushing past that point you're just sacrificing efficiency and stressing the voltage ratings on the regulators on the low voltage electronics by moving to 6S without gaining much if anything in terms of power delivery. 90% of the supposed gains people see in going to 6S is because they're simultaneously going to a higher relative capacity battery that has a higher output relative to the voltage.
The other factor is that due to demand everything currently has been optimized for 6S. Compare the number for 4S 2000mAh batteries to the number of 6S 1300mAh batteries available at the FPV shops for example. Also look around for ~2800kv motors snd compare it to the selection of ~1950kv 6S motors.
Anyway it's a fun discussion, but in the end it's more academic than practical. Anything in close to the right range will work great and fly well, so in the end flying whatever works for you and is readily available is the right choice regardless of the technicalities of why or minor optimizations. Fly what you enjoy and have access to! It's just a lot of the commonly shared info on the topic is inaccurate at best.
I fly a 3" on 6s with tmotors 1507 2700kv and it fly absolutely great and much power it gives👌🏻
I have loads of 3 inch. 1506, 1606, 1507 and 1408 all on 6s. They're superb.
No one said 6S won't work, it's just you end up with a heavier quad with no more power than an appropriately setup 4S rig. It flies fine, it's just not gaining anything and you're losing efficiency and the batteries are small enough in capacity that the cycle life and current delivery can be hit or miss. In general 4S is just the more reliable and effective option, but 6S still will work fine in most cases.
I just can't agree with this. My 4s 3.5 quad is lighter yes but definitely not as fast and not as much power as the 6s version. There is an obvious difference. @@QuadMcFlyFlies
@QuadMcFlyFlies it makes a huge difference with 6s the weight isn't that much more and you feel the power difference. So iam not agree with what you say.
How to get the samll LIPOs ? And which one ?
We use outrunner motors for the torque. People who were there in the beginning should know this. 😉
The real benefit to higher voltage is LESS AMPS for the same amount of work done. Thats why your heavy amp draw household appliances aren’t 110v. Because they draw half as many amps at 220V for the same amount of work done at 110V and your electric meter is charging you for the amp usage.
In the context of mini quads, less amps, means you need less wire gauge and battery connector size for the same amount of work or less voltage drop over the same wire size.
So from an efficiency standpoint and a weight saving standpoint, you should see better and better results as overall mini quad weight goes down… to a point of course
So there's a couple of problems with this analogy. It definitely is true when you're dealing with the kind of power bandwidth that 220A appliances draw, but we're not anywhere near that range with our miniquads. That's kind of the point of what Joshua is saying. Even at 4S we are nowhere near the limits of the wires and connectors we're using for even 5" drones at the highest power levels.
Also we're dealing with a brushless motor and control system that introduces a lot of additional variables when it comes to efficiency, switching losses, limitations of the design and dimensions of the motor to the point where the discussion becomes a lot more complicated.
The short version is after loads and loads of testing, 6S really only becomes useful when you exceed a pretty significant power delivery requirement, otherwise your best bet for efficiency is the lowest voltage that can deliver the power requirement you need.
Maybe I'm wrong, but doesn't the power meter calculate wattage, and the power company charges you by the kilowatt hour? So, a higher voltage but fewer amps would probably still come out to about the same power usage. Or am I missing something?
@@lawrencelovato2253 You are exactly right and I can down here to say it.
We are charged for Volts * Amps, not just amps. So, if you jump from 120 V to 480 V just to save a buck, by dropping the current from 20 Amps to 5 Amps, you would (in this fictional "charged by amperage" world). However, since the USA standard (and probably worldwide standard) is to be charged by power and not current, the cost would be the same.
There's my unnecessarily long response. I like electricity.
I've built 2.5 inch 6s cinewhoop and my reason was longer flight time. But I wouldn't recommend going below 2.5 inch, hell I recommend don't go lower 3 inch if you truly want to be efficient.
I just like using the right motor for the right rating , its less complication, and better flying time, I did put 6s on a 4s quad, it flew ok, but didnt like the difference, it was screaming too much. I have 1 4s quad and its already a beast on 4s, nazgul evoque , aint going nowhere, its my go too quad.
I have s quadmula Djinn 2.5 inch with 3000kv on 650mah 6S and flys great
Awesome
Not arguing but try the quadmula djinn on 6s. You can really dominate your movement against the air.
Up to 1804 size motors you can stay with an 850mah 4s and xt30.
Woth more power hungry 2004 and bigger motors you will want 650 to 850 mah 6s xt30 lipos.
Just my experience from building many many 3 to 4 inch quads.
You can push an xt30 up to 90A burst. No problem. It's only for a few seconds.
Beyond that either change to xt60 and bigger 1200mah 4s lipo or stay xt30 and use 6S 850mah lipos.
Yes AND… lol. You can get away with XT30 and smaller wire much easier on 6S. So if you want to try to get an HD 3 or 4” quad under 250g, you may NEED those few grams of weight savings
You're losing any grams gained on the connector in weight gain on the battery itself in extra wires and balance connector weight, not to mention the cell packaging. Pretty much across the board a 4S build is going to be lighter than a 6S.
That's entirely aside from the point that an XT30 is plenty enough for 4S on 3.5" unless you're planning on carrying a full weight GoPro with full size motors (2204-2305 range) with heavy prop loading. Keep in mind the 30A rating is a constant current rating, and direct testing has demonstrated that XT30s can deliver 60A without issues for the duration of a flight without showing any rise in resistance or measurable losses over an XT60. There's really no need to go to XT60 for any smaller application regardless of voltage on anything below 4" in my opinion. I even run them on my light weight 5" builds.
but what about difference in voltage sag between cell counts?
6s on 3 inch every time for me.
Ballistic.
So i fly 6s on a 21 inch prop and rarely get more than 22 min flight times... its a big ass 36,000 MaH 6s tattu and 320Kv t-motor... what can i do to get better efficientcy (the quad weighs 18.5 pounds)
What are you even doing with a quad that big.
@grandpa_stanley7813 it's for work, can't really give exact details but I just would expect there's a more efficient way to keep it in the air longer. Maybe not though cuz of the weight.
@@WHEATSFPV I think 6s is kinda low voltage to run on a quad that big. Have you considered running 2 smaller batteries in series to make a 12s?
I'd say this... 3", 3S. 3.5", 4S... Bigger, higher.
Well, unless it's a cinewhoop...
Agree for typical tri blade props. But for very high pitch or cinewhoop props you will want more cells and power
@@chrisbee5481 exactly.
So why am I flying 6s on a 21 inch prop
@@WHEATSFPV 21? Out of my League 😆
Lower KV almost always equals more torque...in practice. I will demonstrate:
1. Same voltage eg 2400kv vs 2700kv - Your power limit is the amps the battery can dish out, the lower kv motor produces more torque for the same amount of current, therefore more torque.
2. With different voltages eg 4s vs 6s - manufacturing benefits, also heat build-up effects efficiency, system is power limited so better efficiency = more torque, ALSO the rest of the system doesn't change (typically) the motor resistance might drop proportionally but you don't use different escs, wiring or connectors which also produce losses, therefore lower current = more torque.
TL;DR, system power limitations, motor manufacturing, heat buildup etc all mean that for all practical purposes lower kv = more torque.
There's a lot to unpack in there, but the short version is the primary measure of torque is angular acceleration, not maximum RPMs, and the motor will have very similar angular acceleration of the same mass regardless of the Kv assuming all other variables stay constant in relationship to each other. The relationship between the torque constant (how much current it takes to produce a given unit of torque) and the velocity constant (the angular velocity that produces a given amount of back emf/voltage in the coil) means that the power requirements for producing that torque also balance out assuming voltage is scaled at the same rate. Smaller mAh battery of higher voltage with equal C rating can deliver the same effective current as a larger mAh battery with a lower voltage. Essentially the torque constant is scaling at exactly the same proportion as the current delivery capacity of the battery, which entirely cancels each other out in the torque discussion.
As far as wire losses go, we're actually not operating anywhere close to the ranges where the losses make any significant contributions to overall output at either 4S or 6S, so that discussion is almost entirely irrelevant here.
Short version, there is no appreciable torque difference from lower Kv motors there is only a functional limit due to the relationship between battery's current delivery and the motor's Kt/Kv.
@@QuadMcFlyFlies The point I am making is that there are a lot of what I would call "perfect world" assumptions there that don't really reflect the reality of the systems we use.
"Smaller mAh battery of higher voltage with equal C rating can deliver the same effective current as a larger mAh battery with a lower voltage." - we almost never actually do this. Even if we did there are other system imperfections that tend to make this untrue, lower kv motor construction is (usually) better. IR^2 losses compound each other, reducing overall efficiency which increases power requirements. Do 1800kv motors run at the same temp as 2700kv motors for the same power in practice? Do 2400kv motors run at the same temp per unit thrust as 2700kv motors?
Basically I don't think this assumption: "assuming all other variables stay constant in relationship to each other" is valid...except in very exceptional circumstances that almost never occur in RC and even less often in the extremely power restricted world we live in.
I'd love to see some testing but I do think the system losses need to be accounted for when thinking about this. Even 1% is 1% more power from the battery which increases the sag, which increases the current requirement etc. It's likely the impact is proportional to the increase in resistance squared. The current we use is enough to desolder the connectors we use if maintained for a significant amount of time. Its not the major consideration but I suspect it adds up, especially towards the end of a flight where temps and sag are maximised.
@@frasersteen you're in luck, I've done extensive testing on this over the years, and unfortunately I can tell you that doesn't play out the way you think it does. The issue you run into is the electronics themselves are less efficient as you go up in voltage due to things like switching losses. 6S is pretty much always less efficient than the equivalent 4S setup. And yes, the temperature differences between 4S and 6S at the motor are negligible. I've test over 300 motors with several thousand motor and prop combinations and this holds true pretty much across the board. I have data on the bench as well as pretty extensive flight testing.
BTW, I'm the guy (Ryan Harrell) Bardwell referenced in this video as being the one who knows this kind of stuff :D
@@QuadMcFlyFlies You are indeed a god amongst men and I have watched or read pretty much everything you've published. I'm aware of your expertise and I'm not actually questioning it. You have written about this already on MQTB. What I am arguing is that in the real world we don't use the kind of apples to apples change that the theory depends on. I would also add that your excellent testing, rightly, isolates the motor and prop as variables rather than testing the actual system in use. 100% fair but it does mean that there will be differences when the power is limited by having to share a far smaller battery with 3 other motors.
Your testing indicates that almost universally 6s produces more thrust than 4s even when the listed KVs are equivalent. This is a strong indication of more torque, it's probably not an apples to apples comparison due to manufacturing efficiencies, but it never will be. It also indicates (usually) that the lower kv variant of motors for the same voltage tend to be more efficient per unit thrust. Batteries tend to stay the same so if efficiency increases it will result in more available torque in most cases. Plus even on the smaller quads higher voltage packs tend to be larger overall and greater than equivalent.
Take your point about switching losses but from what I understand switching losses decrease as the duty cycle increases so they will be at minimum when power demand is greatest and resistance is maximised. Some back of the envelope maths indicate you could be looking at 30W of losses in 20cm of 16AWG @35 degrees c &100A vs more like 60W with 150A. 20cm is a lot but with connectors escs and solder joints it felt like a fair estimate.
@@frasersteen I agree that the bench testing is only one aspect, but the point remains that in-air testing also backs this up. The primary thing is that we're not hammered at the top of the throttle except in very rare circumstances. Torque is reflected in flight much more in the rate of change of RPMs rather than the top end thrust. The instantaneous torque capacity of the motors is not going to be impacted the same by the output capacity of the power system, and while you might see a slight increase of peak power depending on your application, the parts of the throttle where most of us are flying are not limited in that way. The expressions of torque that we most care about for flight will have the least difference between voltages in practical application. I do agree that in situation where the limit is the maximum output power of the system a lower Kv motor will produce more maximum sustained torque when it bumps up on that ceiling, but that isn't a situation that impacts flight very frequently, or one that most pilots will actively feel except in a very narrow set of circumstances such as a sustained full throttle punch. Even then if the Kv, battery wattage, and weight are all equivalent to the voltage, difference will be virtually undetectable even in flight without looking at blackbox logs. So you are technically correct that there is a slight increase in the accessibility for maximum sustained torque as Kv lowers when the system is bottlenecked in terms of power delivery.
And yes, you're pretty much accurate on the connector and wire losses. 60W max will disappear in the total 2200+ wattage throughput of the system at 100 or 150A, and we don't spend more than a handful of seconds during a given flight in the > 100A current range. I think Bardwell covered this in a couple of his other videos as well.
Quadmula f25 build help!
DJI o3 air unit
Elrs
Should I go 6s or 4s? I see a lot on 4s and a lot on 6s. Can't decide. Some people ive asked say def get 6s
Should I get the speedybee f405 V3 mini stack to save money or is it worth spending more for the mini t motor f7 stack? Any other recommendations?
Thanks for any feedback or suggestions!
Got the same set up with speedybee in 6s.
I find that I have short fly time and lots of prop wash can't tune it well.
The build is like 256gr.
@@hashikill which battery are you using
Holy smokes 6s on 30mn prop? Sheww
22 min fly time with 21 inch props on 6S? None of that sounds right. First off I’ve never seen 21 inch props. And 22 minutes on a lipo? Never. You sure you didn’t type that wrong?
Who?