Battery questions for my new Flamewheel

GimpyGeek

GimpyGeek

Member
So I am building my first multirotor (all my RC experience is on borrowed toys) and I am trying to figure out which batteries I should be using. I have read some great information on Lipo batteries here, but I still have a question about what I gain or lose by going 3s or 4s.
I have a stock DJI F550 with the 2212 DJI motors, 30a DJI ESC's, Naxa w/ GPS and Senrigan gimbal. From everything I am reading, the F550 can run either 3s or 4s batteries. The gimbal can only run 3s according to the manufacturers site.
A long time ago, I used to work at a battery manufacturer, so I know a fair bit about NiCd, NiMH, L-ion and battery basics, so I am going to make a guess as to what the net effect of the 3s vs 4s batteries would be, but it is only a guess, and I could use some guidance.
I am guessing that a 4s battery, being higher voltage, would give the heli more power to the motors, giving crisper response, whereas the lower voltage will not have the same sharpness. I understand that runtime is mostly a factor of battery capacity, and as I am planning on doing more aerial video and photography, I am not thinking that I will need the 4s batteries, but would be fine with a higher capacity 3s. As for the gimbal, I understand that I could run a low capacity 3s directly to it.
So, is my guess correct or am I off target here?
Thanks in advance!
 

SoCal Blur

SoCal Blur

Member
The difference in voltages also drive what size props the motor can use (and therefore how much thrust can be produced). In addition, the 4S generally will weigh more than the 3S battery so that also will affect your flight times.

Keep in mind that you can use the 4S battery and then use an inexpensive BEC (Battery Eliminator Circuit) to power your gimbal from your 4S battery.

There's not a lot of spec info on these motors, unfortunately:

DJI 2212/920KV
Dimension : 28X24mm
Rating : 920kv
Battery :3S,4S Shaft : 8.0mm
Weight : 56gr (with Prop Adapter)
Standard Current : 15-25A Max Current : 30A
Recommended prop : Li-Poly (11.1V) : 10x4.5 Li-Poly (14.7V) : 8X4.5
Gold connector is included.

You should check out eCalc http://www.ecalc.ch/xcoptercalc.php?ecalc&lang=en so you can play with different values to give you an idea how it affects performance.
 
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GimpyGeek

GimpyGeek

Member
Hey SoCal, thanks for that good info. I forgot about the prop size, which reminds me... I have two sets of props that came with the F550, 8" and 10". According to your reply, the recommended prop for the 3s battery is the 10"? That seems counter-intuitive... I would think that the bigger prop would have more resistance and therefor require more power (voltage) to turn. Am I upside down on that?
And now I have to ask about props... The bigger props are for heavy lifting and the smaller ones are for aerobatics?
I am leaning towards a higher capacity 3s battery, but before I purchase a couple batteries for my desert trip, I want to make sure I get the right ones for my flying desires.
I like that eCalc, but I am not able to find any better specs on the DJI motors than you posted above. It looks like DJI doesn't want to admit to making them...
 

OneStopRC

OneStopRC

Dirty Little Hucker
Best all round prop you can get is a 9x5 Graupner, if you can find them. It is recommended that you use 10" on the 3S and 8" on the 4S. The 4S will spin the motor faster which will make it heat up quicker... I know it is hard to understand but that is the way it is.
 

P

PeterLester

Member
Too much voltage leads to a motor conductor insulation failure while too much current leads to a thermal runaway condition. So in either case the motor fails. Electric motors are designed with a balance of current versus voltage in mind so that the conversion of electric watts to motor output thrust is optimized. And this also enables each motor to be constructed with the least amount of weight and size for the desired output thrust.
More powerful motors need more current and well as more voltage since motor watts equates to motor output horsepower/thrust.
The same applies to ESCs which are rated for both amps and volts, i.e., the #S rating. P = V * I and V = I * R......

GimpyGeek said:
So I am building my first multirotor (all my RC experience is on borrowed toys) and I am trying to figure out which batteries I should be using. I have read some great information on Lipo batteries here, but I still have a question about what I gain or lose by going 3s or 4s.
I have a stock DJI F550 with the 2212 DJI motors, 30a DJI ESC's, Naxa w/ GPS and Senrigan gimbal. From everything I am reading, the F550 can run either 3s or 4s batteries. The gimbal can only run 3s according to the manufacturers site.
A long time ago, I used to work at a battery manufacturer, so I know a fair bit about NiCd, NiMH, L-ion and battery basics, so I am going to make a guess as to what the net effect of the 3s vs 4s batteries would be, but it is only a guess, and I could use some guidance.
I am guessing that a 4s battery, being higher voltage, would give the heli more power to the motors, giving crisper response, whereas the lower voltage will not have the same sharpness. I understand that runtime is mostly a factor of battery capacity, and as I am planning on doing more aerial video and photography, I am not thinking that I will need the 4s batteries, but would be fine with a higher capacity 3s. As for the gimbal, I understand that I could run a low capacity 3s directly to it.
So, is my guess correct or am I off target here?
Thanks in advance!
Click to expand...
 
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kloner

kloner

Aerial DP
generally speaking a stock f550 frame with nothing on it flies bitchen on 3s, add a hero zen and you jump to 4s so it'll get back more within it's flight envelope with a near midstick throttle at hover in manual like it had with 3s and no load,,,,, add much more than that and you want bigger motors like 2814,,,, 900-1000 kv keeps this whole 10" prop and still carry weight thing going, but then you got arms like ours to pump it up to 800mm and it can run massive motors, massive props,,,, still somewhat limited to a nex type camera gimbal.... or less.... the frames only so strong. the add much more than that is like landing gear, third axis, fpv gear, second lipos for gimbals, etc. it's an aircraft, defies gravity, loves any bone you can thrown it, will throw itself at the ground if you overload it..... worse thing that happens is it's all gone right.....

when we run higher voltage packs it relieves the amp draws like a welder does better on 220 than 110, etc. if your single rotor, you probably see 3s 450's along with 12s 450's..... it's all throughout all the branches of hobby to increase voltage to maintain lower amp draws in general on all the parts, power distro, esc's, lipos all matters.

when you get into bigger slower more torqy motors, you can spin bigger props way more efficiently..... i have a stock discovery, been running around at 60 amps continuous a long time on 4s. I recently changed these up with a kit we developed and my same flying style rendered a max of 26 amps continuous on 6s, basicaly like saying a car got 30 miles to the gallon, i put my kit in and it got 65+ mpg..... as a laymen term. in another month were gonna have complete motor, esc and arm packages for this rig that will give it flight times over an hour
 
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R

RichardDoty

Member
The capacity will decide how long it will run, as long as the voltage can satisfied the minimum volt for start the motor. IMO
 

GimpyGeek

GimpyGeek

Member
kloner said:
generally speaking a stock f550 frame with nothing on it flies bitchen on 3s, add a hero zen and you jump to 4s so it'll get back more within it's flight envelope with a near midstick throttle at hover in manual like it had with 3s and no load,,,,, add much more than that and you want bigger motors like 2814
Click to expand...

So I have built the Alware landing gear/gimbal combo, which weighs a little over 1.5 lbs with the GoPro on it. You would recommend a 4s battery at this point? What do you think about running two 3s 2200 50c batteries in parallel? I am guessing that I would still be under voltage with that setup?
 


R

rilot

Member
Just for reference, my F550 with AUW of 2.4kg flies on 4S 5000mAh cells. I run 9x5 Graupners and it flies beautifully.
 

GimpyGeek

GimpyGeek

Member
shoot. shoot. shoot.
Yesterday I went to my local hobby store and spoke to the owner about batteries, and he recommended some 3s 2200mAh 50c batteries, which I bought two of. I took them home and replaced the ends with Deans connectors and started charging them when I saw kloner's post.

Kloner, the batteries that you linked are rated at 25c, please forgive my constant questioning, but I was under the impression that I would need a higher c rating (40+)?

Rilot, what is the c rating of the batteries you are using?

And if I switch to the 4s battery on my rig (with the added weight of the landing gear gimbal combo) will I have to use the 8" props and lose the stability of the 10" ones? I hear everyone recommending the Graupner props, which I will get once I have gotten some flight time under my belt.

I really appreciate everyone's input.
 
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T

Tahoe Ed

Active Member
You really don't need 50C lipos. The max that I have for my MR craft is 35C. Most of mine are at 20C. They all work fine. That is from a F330 to a S800. 4S to 6S. Others may have different opinions.
 

kloner

kloner

Aerial DP
give the packs a shot..... there in the right range

50c 2200 has 110 amp continuous, parralel with another 220 amps cont

25c 5000 pack has 125 amp cont service

an f550 overloaded and crashing prob ably doesn't hit much pas 80 amps, more normal your probably hovering at 20-40 amps max
 

SoCal Blur

SoCal Blur

Member
The 50C batteries will work - of course the down side is the extra weight compared to 25C batteries and the additional cost.
 

GimpyGeek

GimpyGeek

Member
OK, very good information from y'all.

What about the props? The kit came with two sets, one 10" (sticker says 450PRP and 450P10) and the other is 8" (one sticker says 450P08, the other says 330P08). Do you recommend the 8" props with the 4s batteries, or will the extra weight offset the effect of the higher voltage?
 


kloner

kloner

Aerial DP
they use bigger thicker wire, connections, fatter cells with more lithium content...

you want the 4s and 10" props
 



GimpyGeek

GimpyGeek

Member
rilot said:
Those 4S 25Cs will do you just fine. Mine are 25C by the way.
Click to expand...

My friend has a Phantom (first version) and he is using 3s 25c batteries. When he removes his batteries after a flight, they are pretty warm. I just figured with two more motors I would have a higher draw so would want to be able to pull more current than the 25c allows.
 

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