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標題: 請問12仔用3.7V Lipo電會用幾turn brushless? [打印本頁]

作者: derek5 時間: 2009-6-24 22:53
標題: 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！

作者: abba 時間: 2009-6-25 09:50
用3.7V玩？唔會嘛？

作者: pmkpang 時間: 2009-6-25 10:17
我用2cell Lipo行8.5T，23/96齒，Speedmind呔，直路唔快，但勝在夠線性。

作者: mtaristo 時間: 2009-6-25 10:27

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

作者: mtaristo 時間: 2009-6-25 10:29
heard somebody say 3.7 V LiPo in 1/12 use 3.5R to gain back the speed, must use receiver battery.

作者: abba 時間: 2009-6-25 11:25
IFMAR regulation changed?

作者: derek5 時間: 2009-6-25 11:29
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....

作者: abba 時間: 2009-6-25 11:38
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

作者: tekin708 時間: 2009-6-25 12:08
3.5R or 4.5R

作者: derek5 時間: 2009-6-25 15:51

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!

作者: pmkpang 時間: 2009-6-25 22:39
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。

作者: hardmankam 時間: 2009-6-25 23:26
本帖最後由 hardmankam 於 2009-6-25 23:27 編輯

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

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

作者: hardmankam 時間: 2009-6-25 23:40

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.

作者: pmkpang 時間: 2009-6-26 09:47
點解唔用30C呢？

作者: rk2 時間: 2009-6-26 09:57
very surprise to know about this " 3.7V Lipo " to be used in 1/ 12....

作者: hardmankam 時間: 2009-6-26 10:35

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

作者: abba 時間: 2009-6-26 10:36

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......

作者: hardmankam 時間: 2009-6-26 11:08
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.

作者: pmkpang 時間: 2009-6-26 17:44
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

作者: hardmankam 時間: 2009-6-26 18:18

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！
derek5 發表於 2009-6-24 22:53

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Derek5 C-Hing,

If you want to achieve the same/similar speed for 4NiMh+4.5R, it is better for you to try 2S lipo instead. Maybe 2S + 6.5R, you would have similar speed. For 1S, its very difficult to achieve similar speed.

Most people who try 1S is for stock or super stock racing, not MOD racing.

作者: abba 時間: 2009-6-26 19:27

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.
hardmankam 發表於 2009-6-26 11:08

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There are small size 2S. IP and Energy; one piece or split type...

作者: hardmankam 時間: 2009-6-26 22:10
本帖最後由 hardmankam 於 2009-6-26 22:11 編輯

Most of those smaller 2S lipo are only 2000 to 2200mah. I dont know how long these will last when paired fast motors.

for reference: My friend play his RC12 with 2S lipo (~2200mah) + Black pig and can play for 15 mins.

作者: hardmankam 時間: 2009-6-26 22:13
for myself, i play my 1/12 with 2S A123 instead. (2200mah @ 6V) I can play for about 15 to 20 mins. per charge. this is with a 9.5R motor

作者: abba 時間: 2009-6-26 22:19
I am using Novak 10.5R, 1800mah, 25C, playing more than 15 mins...

作者: TP222 時間: 2009-7-2 11:47

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Speedzone Prototype 1 cell LiPo pack

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Categories - Batteries, Electric, Products, Speedzone - add a comment

Speedzone have sent us this prototype image of their upcoming 1 cell LiPo pack, ideal for 1/12 scale and WGT. Specs will be 3.7v, 5000mAh rated at 40C and taking a new approach, this pack will feature in-built bullet connectors, what they claim is a first for a 1/12th scale LiPo pack. General availability is set for late July.

Source: Speedzone [speedzoneusa.com]

作者: micky 時間: 2009-7-2 15:54
4.0 best choice

作者: ringolau 時間: 2009-7-3 09:55
I saw some one play 12R5 with 3.7V Li-Po used Trinity 3.5R . The speed is faster
than NiMh 4 cell.

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