e2548 Power Systems

All things related to 2548 Scale

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Ed Kettler
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e2548 Power Systems

Post by Ed Kettler »

It looks like we have a workable twin solution with the Turnigy 3536 1400 Kv motors and 40a ESCs (lots of over engineering on the ESCs) and we are narrowing down the battery size through flight testing. Right now we have a 4s 5000 that we'd like to down size the weight.

I have a lot of 3S 2200 batteries, and for the winter build season I'd like to create a few e2548 singles that could run 6S by marrying up two packs instead of buying or modifying packs. What <b><u>tested</u> </b> solutions work in a 6S configuration? Stats?

Thanks!
Ed
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Post by crash_out »

I've been working along the same lines, Ed. I haven't done very much testing, but at 6s, you're going to need a motor of about 800kv.

There is a 42-40-750 Turnigy SK, but I suspect that is not enough KV to get you to 14,500...LightFlightRC has a 36mm ARC inrunner rated at 800 kv that should pull it off. I have test run a Himax 3630-780 on 6s, but it's a moderately expensive motor to be running.

Regardless, there is going to be a LARGE difference in amp draw between the 3-pitch APC and the 4 pitch MAS. On some test runs I've done with a Himax 3630-780, the amp draw can very nearly double(18-20 amps versus 32-34 amps).
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Post by Lee Liddle »

For starters, it will take at least 8s 2200 to sustain the 660w needed to do a 2548 single. You could go 9s, but then you are getting into expensive esc.

You`ll either need to buy some 2s to go with your pair of 3s, then you could do 5s2p (pretty heavy) or 8s. Or make some single cells and go 4s2p.

Here`s an 8s motor http://www.hobbyking.com/hobbyking/stor ... otor_600kv

And a 4s motor http://www.hobbyking.com/hobbyking/stor ... tor_1450kv

Image


I have both of these and have bench run them with the MA 10/4. Haven`t flown combat with them, but they should work.

I have flown combat with the Ammo 36-50-1500 when it sold for $35. You need a min of 1350kv on 4s. The Arc 36-55 with the right kv is an excellent motor, but the shaft is pretty soft and it costs almost 4 times more than the Turnigy outrunners.

Nice thing about the outrunners is that they can be repaired. Shafts replaced, windings rewound, magnets glued, and bearings replaced all pretty easily. With an inrunner, you can replace the whole shaft assy (very expensive) and swap bearings, that`s about it.
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Post by Lee Liddle »

BTW here`s a little math to help explain why 6s 2200 won`t do the trick.

You need 660w to turn an MA 10/5 at 14.5k, give or take a little, but basically that`s about 9/10ths of a horse power, which is consistent with what an OS .25 will do.

So if you take your volts (22, it`s always best to round down a little) then divide 660 by 22, you`ll see that you will need 30 amps at 22v to get 660w (amps x volts = watts). For 6s, you`d need at least a 3000mah battery, and a motor with a kv of about 800 to 900. (no less than 800 though)

Well, a good 2200mah cell will give you 30a, but not for 5 min solid. Mathematically a battery can give 12c (2.2a in this case) for 5 min, but it will be completely dead. So really you can only expect to get about 10c for 5 min, and that`s pushing the limits.

30a divided by 2.2a = about 13.6c you`ll only get about a 3.5 to 4 min flight and it will start slowing down at 3 min.

4s (14.4v)....... 660/14 = 47amps.......... 2p 2200 is a 4400 battery .....47a is about 11c which is pushing it but I`ve done it and it works, because your amp draw drops about 10% in flight.

8s (28.8v) 660/28v = 23.5a, again, that`s a little over 10c, but will work.

That`s what you need to know Ed. I could tell it to ya on the phone, but then you`d hang up and go " What the he11 did Lee just say?" So here it is so you can reefer back to it. LOL
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Post by Lee Liddle »

Here`s an example of what would make a good 6s motor. It weighs 6oz, is rated at 770w and it has the SK quality. As long as the KV rating is accurate.

http://www.hobbyking.com/hobbyking/stor ... 0Kv_/_770W

Image

and here`s the battery that you`d need times 2

http://www.hobbyking.com/hobbyking/stor ... _Lipo_Pack

Image
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Ed Kettler
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Post by Ed Kettler »

Lee Liddle wrote:I could tell it to ya on the phone, but then you`d hang up and go " What the he11 did Lee just say?" So here it is so you can reefer back to it. LOL
Exactly :D

Using the watts of the OS 25 is a good starting point ... that was somewhat of a mystery on how you decided what the right choice was going to be. One mechanical horsepower of 550 foot-pounds per second is equivalent to 745.7 watts

Looks like the 4S 5000 we use on the twins weighs almost the same as the combos (in some cases less), so will probably go that route at least for testing.

What setup are you running in the Skyraider?

Thanks!
Ed
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Re: e2548 Power Systems

Post by combatgoblin »

Lee,
From what I have read if you use say a 35-48-900 motor and two 3000mah 3s2c lipos you can turn a 10x4 at 14,500 for 5min
or do you need to go with a larger battery say an 8s2c 3000mah.

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Re: e2548 Power Systems

Post by Ed Kettler »

I have put about 7 flights on my FW-190 with the 3648-1450 motor running off a 4S5000 and it flies great. Need to do some work on the cooling air flow as the battery gets pretty warm.
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dditch
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Re: e2548 Power Systems

Post by dditch »

Very interesting. I"m a Heli pilot mostly so the eVersion of SSC is where I gravitated since I'm mostly electric and have lots of 2200mAh 3S packs.
a 6S 3000mAh pack is very popular (425mm bladed heli like the Align 500 or Align 500 clones). Right now, 6S ESCs are easy to come by and are cheap. Anything over 6S and it gets a little harder. HK sells the 60-70SS that does handle 8S. But I'm more interested in 6s 3000 cause of my battery supply as well as Single battery solution. 9S might be interesting if the availability of inexpensive ESCs were there.

I'm only SSC right now but want to do 2548 next year. I've been flying the Nanotech batteries and I think they are great for e-Combat. They charge up really fast, are lighter, smaller and stay cooler. They also have a very low internal resistance so the voltage drop under load is less (25C acts like a 30C turnigy). This allows a higher Max RPM.

For the ESC, I like the SS series cause of the cost and big heat sink. I've only had one contest w/ it but in my last couple weeks of test flights the SS ESC has not heated up (yea I'm bringing air to it, A hole in the front and a larger hole to exit). ESC and battery should get air in a scale fuse.

Reloading batteries while keeping them protected is a challenge. My SSC planes have that right now so I'd be curious what Scale kits look promissing to be able to reload the batteries and get the CG well?

I"d be looking into this motor:
http://www.hobbypartz.com/monsterpower- ... motor.html

Im using the Monster Power 15 on my SSC even though it's heavier than the SK 1100KV motors mentioned in the SSC section.
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Re: e2548 Power Systems

Post by midair02 »

Ed Kettler wrote:I have put about 7 flights on my FW-190 with the 3648-1450 motor running off a 4S5000 and it flies great. Need to do some work on the cooling air flow as the battery gets pretty warm.
Ed,

How many amps does that setup pull? I don't want to let the magic smoke out of my ESC. :wink:
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Re: e2548 Power Systems

Post by Ed Kettler »

I am using a 60a Turnigy ESC
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dditch
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Re: e2548 Power Systems

Post by dditch »

I flew 2 events with this motor in my Oscar:
http://www.hobbyking.com/hobbyking/stor ... oduct=4912

I used 500 heli batteries
Gens Ace 5300mAh 6S 25C pack.
On the ground, I was easily getting 14500 with a MAS 10x4
On the WAttmeter it was pulling about 650W so it shows up more wattage than it's rate for on the book.
I don't know the long term risks because I've only had about 8 flights on it.
I'm anxious to put my eagletree logger on it because it sure felt like it unloaded pretty good in the air.
It was pulling about 30A on a full pack static on the bench. I know most my electrics will drop the current 10% in the air so that puts it at 27A approximatly.
I have a 60A SS ESC in it.
That 5300mAh pack is pushing it. I MUST dial it down before "start combat" and periodically drop throttle to keep from pushing the limits.

My electric was flying better than my Nitro. It was a shame though, all that power caused me to snap in a tight turn and hit the field
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Re: e2548 Power Systems

Post by midair02 »

dditch wrote:I flew 2 events with this motor in my Oscar:
http://www.hobbyking.com/hobbyking/stor ... oduct=4912

I used 500 heli batteries
Gens Ace 5300mAh 6S 25C pack.
On the ground, I was easily getting 14500 with a MAS 10x4
On the WAttmeter it was pulling about 650W so it shows up more wattage than it's rate for on the book.
I don't know the long term risks because I've only had about 8 flights on it.
If you can get away with a 100 over the max recommended, I should be able to get away with 30 over on this one:

TGY AerodriveXp 25 SK Series 35-42 1250Kv / 630w
http://www.hobbyking.com/hobbyking/stor ... oduct=7072

http://rccombat.net/forum/viewtopic.php?f=54&t=13710
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Re: e2548 Power Systems

Post by Ed Kettler »

I am withdrawing my support 3648 - 1450 ... it just failed to start on Friday with no prior warning, may have a magnet problem. I also lunched two Turnigy 3536-1400s in SSC yesterday. My opinion of Turnigy motors is dropping
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dditch
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Re: e2548 Power Systems

Post by dditch »

I swapped the motor shaft on my Turnigy 4240-900Kv last week and test flew it (6S 3300mAh setup) last friday.
It did not miss a beat, Running strong and easily getting 14500RPMs

I'm so happy with the efficiency of my SSC setup that I'm going to try some Turnigy SK motors on my 2548 Kate.
I have these on order to try (I think lee's old pic of the SK35-48 900Kv motor is outdated):
http://www.hobbyking.com/hobbyking/stor ... oduct=7393
http://www.hobbyking.com/hobbyking/stor ... oduct=7125

I'm hoping the efficiency will be better than the Gold Turnigy which when looking at the smaller .15 sized motors pulls more current than the SK which has better hardware in it. I'll be able to take a static watt meter test to compare them.

I REALLY thing that 6S is better when you get to 2548 to keep the current down.
I just happen to use the 6S 3300 in my Helicopters so that makes it more convenient for me.
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