Li-Polys
07-12-2003, 03:45 PM
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Hello All
First off whats the differents between the E-Tec Li-poly and the Kokam Li-Polys, besides price
Also i ws thinking of getting the 2+2 parallel 2s2p 2400mah 7.2v Li-poly for my Feda, anyone else try this yet, or should i just stick with the single 2-cell 7.2 pack
First off whats the differents between the E-Tec Li-poly and the Kokam Li-Polys, besides price
Also i ws thinking of getting the 2+2 parallel 2s2p 2400mah 7.2v Li-poly for my Feda, anyone else try this yet, or should i just stick with the single 2-cell 7.2 pack
07-12-2003, 05:37 PM
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Hi Simbo nice to see someone else from CT, anyway the Etec's seem to have the higer output from what I've seen but there are some high out put Kokams out also you should be fine with a 2S 1200mha pack , most of the guys like Hoverup,Kenru,Dodgey99 etc. are using them and getting 20 minutes or so in flight times on them. they are about half the weight of the stock pack so you'll have to rebalance your Heli, some are mounting very far forward up under the canopy or slung underneath out in front
07-12-2003, 08:48 PM
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Attila,
Li-Poly is short for Lithium Polymer, which is actually a type of Lithium Ion. It is a different battery chemistry. They are one of the greatest things to happen to electric flight. They have much more than twice the capacity of NICAD and NIMH batterys of the same weight, but they do require special chargers to charge them safely.
Simbo,
The Etec's will work at a higher discharge rate. The standard 1020mah Kokams just don't quite handle enough current for the stock Feda. You could use 2S2P 1020 Kokams, but that is a lot of extra weight. Most people are really happy with the 2S Etec 1200mah for the Feda, reporting 15 to 20 minute flight times.
Jeff
Li-Poly is short for Lithium Polymer, which is actually a type of Lithium Ion. It is a different battery chemistry. They are one of the greatest things to happen to electric flight. They have much more than twice the capacity of NICAD and NIMH batterys of the same weight, but they do require special chargers to charge them safely.
Simbo,
The Etec's will work at a higher discharge rate. The standard 1020mah Kokams just don't quite handle enough current for the stock Feda. You could use 2S2P 1020 Kokams, but that is a lot of extra weight. Most people are really happy with the 2S Etec 1200mah for the Feda, reporting 15 to 20 minute flight times.
Jeff
07-12-2003, 09:58 PM
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Thanks Jeff, I just got my RCM and noted an add for such batteries. The chargers are very reasonable. I will try a few to see about them...Seems like only drawback is a two hour charge time. Thanks again for responding to my question...
07-12-2003, 10:34 PM
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I have heard that the 2 cell 1200 is less weight then the stock battery, and that folks have had to move the battery more to the front for balance, hence going with th 2x2 2400 pack may be the same weight ?
Hello Zflyer
Maybe someday we can hook up and you can teach me to fly these things LOL
Hello Zflyer
Maybe someday we can hook up and you can teach me to fly these things LOL
07-12-2003, 11:31 PM
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The eTech 1200 (2s) is indeed lighter but not so much so that it'll throw the balance way off. I'm using a pair of those right now and they are great. I would imagine a 2s-2p pack would be too heavy. The 2s pack mounts on the front end of the battery rails and tucks up nicely under the canopy. The decrease in weight does help flying too. I'm getting 20 or more minutes of flying time. Worth the money and wouldn't go back!
07-13-2003, 12:39 AM
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LOL just as soon as I Learn How Simbo, Still trying with my HBird but I seem to wreck something new each time I think I've got it. This time it's the main and pinion gears was a little slow on throtle cut when I swung it into the couch, a Speed 300 has quite enough torque to put a flat spot in the main in about a second and a half also decreases the diameter of the pinion in the same amount of time. I have a new main but I'm fresh outa pinions LOL
07-14-2003, 02:40 PM
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Hi guys, Hi Z!
You won't get off the ground with 2s2p. Too much weight.
Trust me, for a FP heli like the HB or Dragonfly / skylark you want 2s.
Go to Bishops power products. I got my batts and charger from them . Their service is perfect.
They take 1 not 2 hours to charge (usually 40 mins as you never fully discharge lipos)
If you go to CP (i.e. pic pro) then you want 3s. I sold my 2s on ebay and got what I paid 4 it.
Lipos rock. You will NEVER get pissed off with batteries again.
You could go straight for a 3s but unless you are brushless you'll chew through main motors with the higher voltage. I found 2s to be perfect for a stick hummingbird. When I went separates and brushless 2s was not enough. My Pro flies like a wasp!
Also, as you only need 1, u can install it permanently in your heli so you don't have to dick around setting the CoG all the time.
I get 20+ mins on hum and pro (no lunger fly the hum)
Go for it!
You won't get off the ground with 2s2p. Too much weight.
Trust me, for a FP heli like the HB or Dragonfly / skylark you want 2s.
Go to Bishops power products. I got my batts and charger from them . Their service is perfect.
They take 1 not 2 hours to charge (usually 40 mins as you never fully discharge lipos)
If you go to CP (i.e. pic pro) then you want 3s. I sold my 2s on ebay and got what I paid 4 it.
Lipos rock. You will NEVER get pissed off with batteries again.
You could go straight for a 3s but unless you are brushless you'll chew through main motors with the higher voltage. I found 2s to be perfect for a stick hummingbird. When I went separates and brushless 2s was not enough. My Pro flies like a wasp!
Also, as you only need 1, u can install it permanently in your heli so you don't have to dick around setting the CoG all the time.
I get 20+ mins on hum and pro (no lunger fly the hum)
Go for it!
07-14-2003, 03:41 PM
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But...???
Isn't the stock cutoff voltage for the ESC too low (dangerous for Li-Polys)?
What about max current? Li-Poly = 4A then poof!
Anyone know the peak sustained current for the stock hummingbird? I have one and would like longer flight time....
What about max current? Li-Poly = 4A then poof!
Anyone know the peak sustained current for the stock hummingbird? I have one and would like longer flight time....
07-14-2003, 04:21 PM
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Jim,
The Kokam 1020 cells will handle about 3 amps. The Etec 1200 cells will handle about twice that. They don't go poof if you exceed that by a little bit, the just don't perform well. The stock HB pulls around 4 amps, so the Kokams are not a good match, but the Etec is just about perfect, with around 20 minute flight times.
As for low voltage cutoff, the heli will probably stop flying before the batteries get so low as to damage them. If you stop flying when it gets hard to climb, you should be OK.
Jeff
The Kokam 1020 cells will handle about 3 amps. The Etec 1200 cells will handle about twice that. They don't go poof if you exceed that by a little bit, the just don't perform well. The stock HB pulls around 4 amps, so the Kokams are not a good match, but the Etec is just about perfect, with around 20 minute flight times.
As for low voltage cutoff, the heli will probably stop flying before the batteries get so low as to damage them. If you stop flying when it gets hard to climb, you should be OK.
Jeff
07-14-2003, 05:10 PM
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Exactly. it is Sooo obvious when the lipos start to lose power, then you land. Believe me, it is more than obvious.
There is a lot of panic about this. I have the lo volt cut off set to the min of 4v on my Phonex 10 esc. Never reached it.
Never had problems with my hummingbird with the stock hummingboard either.
There are 1oo's of people super happy flying lipos. Don't fret. It works.
"What about max current? Li-Poly = 4A then poof! " - strange statement if you consider a search here or elsewhere will yield 100's of happy people running li-po's on micro helis.
And as for current draw... you should see my Pro on a 3s e-tech pack. Nothing gets even warm, but it performs like you would not believe...!
There is a lot of panic about this. I have the lo volt cut off set to the min of 4v on my Phonex 10 esc. Never reached it.
Never had problems with my hummingbird with the stock hummingboard either.
There are 1oo's of people super happy flying lipos. Don't fret. It works.
"What about max current? Li-Poly = 4A then poof! " - strange statement if you consider a search here or elsewhere will yield 100's of happy people running li-po's on micro helis.
And as for current draw... you should see my Pro on a 3s e-tech pack. Nothing gets even warm, but it performs like you would not believe...!
07-17-2003, 08:37 PM
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Thanks for all the info guys, but
My heli don't fly no more, had a small crash from only 3 feet high, and now it has lost the ability to lift off the ground, seems to only get up to half speed, all controls seem to work, can skid on ground forward, back, side to side, and yaw but not enough main rotor speed to lift off, don't have a gauge to check pitch, paddles seem to be level, and main blades are fix pitch, thinking maybe motor, speed control, paddles, or battery.
Grounded for awhile
Stinks being a newbe at this stuff LOL
My heli don't fly no more, had a small crash from only 3 feet high, and now it has lost the ability to lift off the ground, seems to only get up to half speed, all controls seem to work, can skid on ground forward, back, side to side, and yaw but not enough main rotor speed to lift off, don't have a gauge to check pitch, paddles seem to be level, and main blades are fix pitch, thinking maybe motor, speed control, paddles, or battery.
Grounded for awhile
Stinks being a newbe at this stuff LOL
07-18-2003, 11:48 AM
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3 feet doesn't sound like enough to bend anything. I was flying outside last night and it got a bit gusty, I hit the dogs pool from fast forward flight. Picked it up, plugged the landing gear back in and went back to riding the gusts. 
Does it sound the same, are the blades turning as fast as they used to? Have you tried twisting the blades as shown in the instructions?
Does it sound the same, are the blades turning as fast as they used to? Have you tried twisting the blades as shown in the instructions?
07-18-2003, 12:58 PM
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Simbo,
You might check the gear mesh (back lash) between the main rotor motor and the big gear. Heck, check the mesh of the tail rotor too. If the mesh is too tight, it will put a lot of extra load on the motor(s). A small crash like you had may be enough to shift the motor slightly and cause that sort of problem...
You might check the gear mesh (back lash) between the main rotor motor and the big gear. Heck, check the mesh of the tail rotor too. If the mesh is too tight, it will put a lot of extra load on the motor(s). A small crash like you had may be enough to shift the motor slightly and cause that sort of problem...
