Tattu 6S2P 7000mah 15C battery LHS setup

[Wammied]

Hi everyone, long time lurker Mike here.
I'm the proud new owner of a (used, 6 flights) KDS Agile 7.2 heli
It has a Castle Creations Phoenix Edge HV 160 ESC and a sep. BEC.
The motor is a KDE 535Kv .
Batteries are 2 6S Turnigy 5000mah wired as 12S

With the current (pun intended) 12S setup, the former owner says it's good for about ~4min. of 'mild' smackin'.
(I have no idea what the motor pulls, need the Castle link to look at the log,
but I'm guessing, based on run time 100-120amps?)
Being that I'm not a total 'smackdown pilot' (decent ticktocks, no piro-flipping (yet,
I'd like the longer flight times (lower head speeds) that 6S offers.

Sooo, I've found these 7000mah 15C bats on sale (sale ends today),
http://www.genstattu.com/ta-15c-7000-6s1p.html
and am thinking if I wire them as 6S2P, I should get 30C (210amps=7ampsx30)
That would be 14,000 mah, good for maybe 12mins?
Am I correct, in that the C rating would double from 15 to 30 with a parallel pack?
Would this work?
Thanks for any help guys

[Ozzy Mozzy]

I have an Agile 7.2 setup for 12s with a Heli Jive and Pyro 700-52. I get around 5-6 minutes at 1700 head speed

On one 6s 5000 pack I get about 10 minutes at 935 head speed

What head speeds are you wanting on 6s?
The weight of 2 packs will need to considered!

[Wammied]

Hi Ozzy and thanks for the reply.
Wow, 935 and 10mins on one bat.!
I'm wondering if you run the 18 tooth pinion?
and maybe have possibly dialed back your throttle curve?
(I checked out you ESC but was unable to determine if it's freewheeling or not)
Also, what size main blades are you running?

The Castle is not freewheeling, and I've read that less than a 70% curve will make it very hot. I've got the 20 tooth pinion 690's and I know it runs 2100rpm at 100% throttle curve.
So I'm thinking, everything else being the same, I should get ~1050 on 6S?

That said, if you're getting ~10min on 6S 5000mah,
I should get ~25min on 6S2P 14,000mah?
(minus the extra weight, call it 20min) maybe way overkill....
Problem is, I already pulled the trigger on 2 15C batteries ($80 apiece on sale
I know 15C is only 105amps and probably not enough with one,
but I thought it would work at 2P (30C)
Ok, so a bit heavy, but huge flight times!

Pefect for extended inverted hovering practice etc.,
or just cruising around 'big sky' style, taking in the sights with the gopro

[Ozzy Mozzy]

I'm using a Vbar Controller, I Can't remember what Throttle % I had for 935 hs

Main blades are Cyclone 715mm
Motor Pinion 19T

I think from memory 90% throttle was about 1100 hs which was ok for some slow 3D (rolls and flips)

[TdB]

A 700 size helicopter with one single 6s pack is extremely effecient and will give you longer flight times, due to the low weight.
Putting 2 6s packs in the frame takes away the effeciency, so this will not double your flight time.

Like a previous member said: a single 6s 5000 can get you 10 min.
So with a single 6s 7000, you should be able to get 12 min, or even longer!

You are not correct that the C rating doubles, it is still 15 C
But where 12s1p 7000 mAh at 15 C gives you: 7 x 15 = 105 A continuous, a 6s2p 7000 mAh at 15 C gives you 7 x 2 x 15 = 210 A.

So the capacity gets you higher discharge rates, not the C rating.

My advice: fly low headspeed with a single 6s pack, it leaves more room for margin, given the low weight.

Flying a 700 size at 1000 RPM fully loaded (with 2 6s packs) can be very tricky.

[Wammied]

Thanks for the responses guys.
Ozzy, your numbers are encouraging:
if you're getting ~1100rpm at 90% with 715's and a 19 tooth pinion/530Kv motor,
Maybe I'll get a bit more rpm. Just guessing, without doing the math, probably 1200~1300+ with 690's and a 20 tooth pinion/535Kv motor?
Do you know how many amps your setup is pulling?

TdB, I'm hoping that 15C (105amps) on a single 15C pack is enough.
I still need a castle link to be able to check current draw,
Ozzy reported he gets about 10min on one 6s 5000 pack at 935 head speed.
If he's taking it down to 20% capacity, that's 4000mah/10=28 amps that he's drawing?
If 15c/105amps 6S is not enough, I'm hoping that with a bit higher head speed using the 20 tooth pinion and 690 blades/535Kv , will help offset the weight of two batteries.
Again, I'll only be practicing piro'ing hovers upright
and inverted for the most part w/this setup.
(I've already purchased these batteries, so hopefully I'll be able to use them!)

Biggest question: Is 105amps continuous enough for non-agressive flying?

[Ozzy Mozzy]

My Motor is 520kv and I go down to 30% on the pack

Can't remember what peak amps I was getting, I would have to check my logs. I doubt they would ever have been close to 100amps though

TdB is right, you are going to feel the weight of that extra pack.....

Best thing you can do is try it with one 6S pack and then try it with 2 of them, see what you think....

[Wammied]

Hey thanks Ozzy, 520 means my 535 and bigger pinion should give even more rpm, maybe 1400-1500. I'm hoping the only effect on 6S 15C will maybe be a slower spool up time, and not a hot battery.
As far as weight of 2 bats at 6v, this thing is so powerful to begin with, it'll probably feel like my old X-Cell .60 bent frame!
(if I can get 1400-1500 out of it)
Oh, one other thing, does your heli 'list' to one side, with one battery in it?
Or does your FBL compensate for it?
Anyway, I should be able to test things out in the next week or so.
I'll post my findings then.
Thanks again you guys

[Ozzy Mozzy]

Remember my 10 minutes was at 935 HS with one pack (nice and light)...... Higher HS shorter flight times and then add the extra weight of an extra pack.... it will be interesting to see what you get! When are you going to test this out?

I was surprised with one pack on the side, didn’t even notice it!

[Wammied]

While it's true I'll have a higher head speed with the 690's and the pinion,
that will def. help with the weight.
I think if I get 1400rpm, I'll be good.
(I think I have seen others running 1400 on 12S with a reduced throttle curve (free wheeling ESC's) with good results, doing waaay more than I plan too)
As for reduced flight time with the higher headspeed,
I'll have 11,200mah's to play with (80% of 14,000)
I hope to test things in the next week or so

[TdB]

Keep in mind that with a smaller rotor diameter, you also drop down in lift and efficiency.

The wider the rotor, the lower the rpm, the more efficient.
(as long as other variables such as blade chord length and blade airfoil remain the same)

[trillian]

Originally Posted by Wammied

Biggest question: Is 105amps continuous enough for non-agressive flying?

It should be, given the right headspeed and, as you say, not being aggressive on the pitch.

My Minicopter Triabolo is a fairly heavy old thing, it ends up very close to 6kg with a pair of 5000mah packs. I'm flying it on 12s at a headspeed about 1290 (according to Mr Mel's headspeed calculator). And the average amps drawn is around 30-35. So if it was running 6s it would need roughly 60-70 amps to get the same wattage.

It's not at all sluggish at that headspeed either, the comparison is a little different because it has three blades but at the end of the day it comes down to a certain amount of watts required to lift a given mass and sling it around.

[Wammied]

Hey thanks trillian that is great news/info!
Just learned of Mr. Mel too, thanks for mentioning that.
Mr. Mel says that, at 85% efficiency (guessing)
I should get a mid-flight hover rpm 1433 with my gearing on 6S.
With 14amps of 6S2P weighing just few ounces more than the "stock' config, and ~1400 rpm, I think I'll be in good shape for some moderately aggressive, extended flying.
Thanks again, I will for sure post my results when I get some!

[Wammied]

So I was finally able to finish and test a 6S2P setup on my KDS Agile 7.2
Only had one test flight, this morning, as my spotter had to leave.
(can't fly alone at my club)
Don't have a tach but it seems to make about 1000rpm
with the throttle curve at 100%.
It is a little bit wobbly in the hover but smooths out perfectly in FF,
and most importantly to me, hovers inverted without any wobbling.
(I thought I had a 20 tooth pinion, I was mistaken, it's a 19.
Think I may get the 20 for a few more rpm.)

Only flew for ten minutes with some flips and rolls and came down only having used 2200 out of 7000mah (2X).
Should be good for 20 minutes easy!
Doesn't seem 'too heavy' with that setup, as it still climbs out with authority and still do some 'big air' immelmans and cuban eights.
Inverted punch outs are respectable.

Loooove the way it sounds and I think an overall perfect setup for me for protracted inverted hovering/muscle memory training.
So there it is, if you want some decent twenty minute flights,
on cheap ($80) 15C batteries, go ahead on 6S2P (and maybe a 20tooth pinion for the wobble), the weight is not an issue.
Thanks again for everyone's help,
learning lots about modern electric helis!
Mike

[Ozzy Mozzy]

Good to know!! I might try a couple of 6s packs next time, I'm curious now....

[Wammied]

Hi Ozzy
After some more test flying, I've discovered that flying with one pack does all but eliminate the wobble. This is flying 6C on my 12C setup (1800,1900,2100) It will blow the tail out after 4-5 tic tocs but that's about the most extreme I do with it.
I much prefer to fly it a scale manner on 6S. It seems to look and handle in a more scale-like fashion than HHS. Making a pass down the center of the runway, the nose seems to be noticeably lower for a given airspeed, appearing more scale-like. Also, you can really just about 'feel' it, when that beast comes down the runway! Between that, the swish swish blade noises, and the flight times (timer set for 9.5 min. and come down with ~30% in a 7000mah pack), I'm lovin' this setup!

[Ozzy Mozzy]

Yeah I love the sound of the blades at 1000 and Its a very relaxing long flight....

I recently got a Logo 600 and set it up for 6s, lowest HS I use on that is 1400, I get about 8 minutes! it's becoming my go to Heli.....

[trillian]

Good to hear it's going well Mike.

I remember the first time I saw a heli at low headspeed was prob about 4 years ago and someone was flying a TDR and I loved the sound of the blades when doing an aileron roll etc. I was fascinated by it.

My next project is a Suzi Laos 800 (this was a very limited production frameset and canopy using Trex 800 head and tail, bearing blocks etc.) I have seen a video of a Suzi Laos at something seriously low, like 700rpm). Anyway it should be interesting and will be my first 800 size heli.

[TdB]

800 size helicopters should definitely be able to go as low as 700 rpm.
I'm interested in a video (with sound of course ) if you manage that!

Btw, I can recommend not using the DFC head, to much stress on the links!

[trillian]

Originally Posted by TdB

800 size helicopters should definitely be able to go as low as 700 rpm.
I'm interested in a video (with sound of course ) if you manage that!

Btw, I can recommend not using the DFC head, to much stress on the links!

Yeah the DFC head might get changed by the time I outfit all the electrics. I'm trying to connect with other owners for tips and stuff.