請問12仔用3.7V Lipo電會用幾turn brushless?

如題:
我現在用4cell就用4.5 turn brushless, 但想要回同樣的速度，唔知道用SMC個隻3.7V Lipo要用幾turn呢？ 謝謝！

用3.7V玩？唔會嘛？

我用2cell Lipo行8.5T，23/96齒，Speedmind呔，直路唔快，但勝在夠線性。

用3.7V玩？唔會嘛？
abba 發表於 2009-6-25 09:50

                               
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why not?  

BMI Racing DB12RR LiPo Edition


As the use of LiPo batteries in the 1/12th scale class has been gaining ground and sanctioning bodies and manufacturers have begun standardizing cell formats, BMI Racing have finally developed a new version of the DB12RR for this class. The LiPo edition features a lower chassis that has been optimized to locate and retain a 4000mah 3.7v LiPo pack. The chassis has had the slot dimensions adjusted to match the pack as well as pocketing of the chassis to lower the pack for optimum center of gravity.

from bmiracing.com

heard somebody say 3.7 V LiPo in 1/12 use 3.5R to gain back the speed, must use receiver battery.

IFMAR regulation changed?

SMC唔係有1C Lipo 3.7V囉~ 聽講要加novak個件booster就可以了，不過就唔知用幾turn brushless....

Even you use 3.5R in order to have speed gained, the efficiency will be low as it isn't the purpose of those high speed motor designed for....any valid reason to use 3.7V

3.5R or 4.5R

3.5R or 4.5R
tekin708 發表於 2009-6-25 12:08

                               
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ching, have you try that before? is it the same speed as using 4 cells? thanks!

師兄，其實我諗應該係咪要睇埋隻魔打嘅Kv值呀。RPM＝Kv×V
用Novak 8.5T，Kv＝5000，用1cell 3.7V RPM＝18500 RPM，用2cell 7.4V RPM＝37000 RPM
用好盈 8.5T，Kv＝4000，用1cell 3.7V RPM＝14800 RPM，用2cell 7.4V RPM＝29600 RPM
再計埋Roll Out嚟揾個靚仔嘅Gear Ratio末得囉。

From westerner's forums, people usually run 1S lipo with higher turn motors (like 10.5 or 13.5).  The main reason is because for lower turn motors, it requires a LOT of power from the battery. In single cell lipo, it may not be able to provide that power... causing the battery to fail.

Here is my understanding:
eg: 4.5R motor usually needs 450watts
Power = Voltage x Current  ... so in this case Current = 450W / 3.7V = 121A

In order to provide ~ 120A, the lipo needs to be at least 5000mah@25C.

Note: the current SMC 1s Lipo is 4000mah@25C

Can't see the reason to use 1S.....

Can't see the reason to use 1S.....
abba 發表於 2009-6-25 23:33

                               
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Westerners are trying out 1S + 10.5R.  The speed is similar to 4Nimh + 13.5R
With 1S lipo, the car is lighter and less wear on the tires.

點解唔用30C呢？

very surprise to know about this " 3.7V Lipo " to be used in 1/ 12....

點解唔用30C呢？
pmkpang 發表於 2009-6-26 09:47

                               
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SMC's current 1S lipo is only 25C.   maybe later they will make higher C while have high mah

Westerners are trying out 1S + 10.5R.  The speed is similar to 4Nimh + 13.5R
With 1S lipo, the car is lighter and less wear on the tires.
hardmankam 發表於 2009-6-25 23:40

                               
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Lipo itself is very light. I think the different between 1S and 2S isn't significant. But the speed will be highly affected. In addition, ESC may need something to do to cope with the lowered voltage. Still don't understand the advantage of using 1S......

The problem of 2S is not the weight, but the size of lipo.  If they can make 2S smaller with a high C and high mah, then it is much more flexible than 1S.

1# derek5


If my calculation is correct;
assume your 4.5T motor has 9000Kv, with 4.8V you'll get 43200RPM,
with factory recommanded rollout, max speed equates to 79.05Km/h

if using 3.5T, 10500Kv at 3.7V, you'll get 38850RPM
with factory rollout, max speed around 65.35Km

May need to sacrifice heat and accelaration when re-gearing to the same speed