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e-Century Hummingbird - Swift > How hot after summer flight should a123s be?
 
 
dwb
Heliman
Location: Orsières ch

My Posts This: Topic  Forum		Hello all!
Just have to rant just a little, love my swift,a123s and dx6i!
But I start to worry about how hot the a123s get after warmer air temp flying.
I run only 5s a123s in my swift with 550+ motor,100amp esc,slow forward flight,lots of hover orientation practice.
I have a habit of checking esc, motor,a123s after flights.
You can easily touch and leave your finger on both esc and motor, but a123s seem to be getting hot.
I understand that I should feed this motor 14.8 volts and that under load my 5s a123s are only giving 13.5, is this the problem?
Must add I am flying in much warmer air temps now as well.
Thanx for any advise!
David

Sorry, another observation, question.
Is it normal that the main blades and flybar do not spin in exactly the same parallel planes?
I have adjusted the head as best as I can?

MCX, LAMA V3,SWIFT 16,DX6i,RF G 3.5
06-17-2009 06:48 PM
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Ben-T-Spindle
rrProfessor
Location: Central Illinois

My Posts This: Topic  Forum		You need to make a 5s2p or 6s2p pack.
Your 5s1p is way too small.



... BTS
06-17-2009 07:36 PM
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CompyMike
Senior Heliman
Location: sacramento, ca

My Posts This: Topic  Forum		I run 10 A123 cells in my swift. But I am at 36 volts. Try out a 5s2p. Get longer flight times and the pack wouldn't be worked as hard. Or just add a cell to your 5 cell pack. Make sure your esc can handle that voltage. Headspeed would go up a little. So either enjoy the more power or drop your headspeed and have longer flight times.
06-17-2009 07:55 PM
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wrathofkhan
Veteran
Location: LA, CA - US

My Posts This: Topic  Forum		I also run 10s1p configuration.

I am not sure if the 550 motor can handle the weight of 5s2p. I am also curious about the amp draw in your 5s1p setup (or for that matter even for 5s2p, if you decide to go that route).

Just a rough calculation:

Say for example if your system draws 1,000 watts during some maneuvers, for a 5s1p (13.5v) it would be around - 74 amps (1,000/13.5). Most likely you are not drawing that kind of continously, but it must have stressed the batteries, that is why I am guessing they became hot.

As far as I recall, the cell voltage drops way below 2.7 - around 2.1-2.2 v/cell. If you calculate using these lower voltage, you will see that the amp draw for each of the cell is quite high.

It's too bad my computer crashed and I lost all my data, but as far as I can recall, I was drawing over 1,500 watts easily on my 10s1p setup - but then again 10s1p is about 400g heavier (plus I am using a bigger motor).

hope the info helps.


cheers, khan
06-18-2009 04:50 AM
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dwb
Heliman
Location: Orsières ch

My Posts This: Topic  Forum		Will 6s a123s hurt a 550+?

Thanx for the thoughts.
I considered 5s2p but also thought it would weigh to much, and for now I do not mind 6, 4 min flights.
I had also thought of testing a 6s a123 but as I understood that a123s give 2.7 v under load and the 550+ is rated lipo 4s, 14.8 volts,and the 6s a123 would do 16.2volts,would this not be good for the motor?
thank you
David

MCX, LAMA V3,SWIFT 16,DX6i,RF G 3.5
06-18-2009 08:29 AM
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wrathofkhan
Veteran
Location: LA, CA - US

My Posts This: Topic  Forum		I am sorry, I am not familiar with the 550+ motor. Do you have the specs on the motor? As far as I know, Swifts can come with that motor for 4s - I tried looking it up on century site, but couldn't find the specs.

Basically, you should multiply the kv rating of the motor with the expected voltage, this will give you the expected RPM. And then you compare the expected RPM with maximum RPM of the motor.

as far as hurting the motor, i can not say for sure. but my guess is, it will not. under stress, the a123 will drop way below 2.7v (and from my calculations, i am pretty sure you are stressing the batteries way more than the ESC/motor - otherwise, they would get hot too). say if you drop the voltage to 2.2, your rpm will go down accordingly. i am guessing that is what is happening.

i have a trex 450 with 3s config. the drop in voltage is significantly higher than on my swift. i am afraid, the same might be true in your case since you also have a low cell count on your swift. i still find it very interesting that a 5s a123 actually can fly the swift for 4 minutes

cheers, khan
06-18-2009 09:03 AM
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e-Century Hummingbird - Swift > How hot after summer flight should a123s be?
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