Li-poly for Hacker B20 4.1 HELP - RC Groups
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Sep 20, 2003, 09:35 PM
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Li-poly for Hacker B20 4.1 HELP

Hey evrey one. I need some help. I have a Hacker B20 4.1 wiht a C.C. 35 speed control.
I want to no if there are any Li-poly's that I can use with this setup any and all help would be gerat Thanks Jeremy
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Sep 20, 2003, 09:44 PM
The Magician.
birdofprey's Avatar
Welcome to RCGroups.

What kind of airframe and which B20 do you have? There are a number of different B20 motors that use different numbers of windings as well as Long and Short cans.

Sep 20, 2003, 10:32 PM
Registered User
Donald Duck's Avatar

Li-Polymers with Hacker B20 4:1

Sure you can use Li-poly batteries with the Hacker B20-4:1. Two LiPo batteries in series will be about the same as 7 NiMH cells. Three in series will be about the same as 10 NiMH cells. However, you have to worry more about the current draw. Assuming you use 1200 mAH LiPo cells, depending on the propeller and the current draw by the motor needed for the speed of your plane, you may have to go to 2 or even 3 LiPo parallel sets of 2 or 3 LiPo cells in series --- that is, 2S2P or 2S3P or 3S3P. I run a Hacker B20-18L/4:1 on 10x1100 mAH NiMH cells, drawing about 13 amps at full power for a 9x6 APC-e prop. To match that with LiPo cells, I would probably try 2S2P to start, then if I needed more power, go up in series. Increase the number of parallel cells if the LiPo cells get too hot with the required current draw.
Sep 22, 2003, 12:41 AM
Registered User

Thanks For the reply's

I have this setup in a Airwave Design Sukhoi 3D the motor is a B20 22L 4:1 and the prop is a 11 X 4.7

Thanks Guy's
Sep 22, 2003, 04:06 AM
I use 2 Hacker B20-15L motors with the 4:1 gearing in some of my 3D models.

With this motor and a 9x6 prop on one plane with an 11x3.8 prop on the other, static current draw is 20 amps on 3s LiPos (Same power as 10 cells). This is far too much for the 1200 mah LiPos...2p does help, but I prefer to use a 3s 2100 mah Thunder Power pack. This pack easily handles 20-25 amp burst for short verticals and is capable of 12.6 amps continuous.

But, both airplanes only weigh around 16 ounces so most of the flight is spent around 1/4-2/3 throttle which makes flight times 15-20 minute easy per charge. With 30 ounces of thrust, both models have AWESOME vertical - the 9x6 is good for speed, the 11x3.8 is great for slow flying but great pull and acceleration.

With any Hacker B20 motor, the Thunder Power 2100s are your best bet when pulling 15-20 amps static. Use 3s for the power of 10 cells, and 2s for the power of 7 cells.

You can get these Thunder Power packs at your local hobby shop (they can order them from Horizon for you), or at these sites:

And many others too!

Last edited by LVRCFlyer; Sep 22, 2003 at 04:11 AM.
Sep 22, 2003, 04:09 AM
I think the Thunder Power 3s 2100s will be perfect for your 22L motor - only weighs 4.5 ounces with 2100 mah and the power of 10 cells

Sep 22, 2003, 08:16 PM
Registered User
Donald Duck's Avatar

Li-polymers in parallel

If you use three 1200s in series, and two of those packs in parallel, you will do fine on a Hacker B20 15L. I am flying a SR Batteries X250 model on 10 1100 mAH NiMH cells, with a 8x6 APC-e propeller. It draws between 11 and 12 amps at full throttle. I plan to replace the NiMH batteries with LiPo, in a 3s2p configuration of 1200 mAH Etec cells. The use of two parallel LiPo packs will reduce the current draw from each pack by 50%, while maintaining the voltage. That means each pack will be putting out about 5 to 6 amps at full throttle, or roughly 5C, which should work o.k. Most of my flying is at about 3/4 throttle. Replacing the NiMH battery with the LiPo packs will reduce the weight by 2.5 ounces, which is pretty significant for a 24 ounce plane. However, I cannot disagree with the use of 3s Thunder Power 2100 mAH cells, but I already own the Etec 1200s.
Sep 22, 2003, 09:14 PM
Registered User
Clayshobbies's Avatar
The Thunder Powers would be great. I use the 3s 2100 with my BP20-15L and my new Himax.

Plus I sell them for $5-$10 less then the 4 venders above
Sep 23, 2003, 12:22 AM
Registered User


Wow!!! Thanks to all. This helps me out so much. Jeremy
Sep 24, 2003, 11:10 AM
texan's Avatar

I'm running a Hacker B20 15L 4:1 with a 10x4.7 prop in a Wattage Crazy 8 on KOKAM 3s3p 1020 LiPo pack. Performance is excellent ... saved about 9oz from the previous 10cell cp1300 setup. Controller is Hacker 30 amp.

Sep 24, 2003, 01:27 PM
Tim H.'s Avatar
Originally posted by Clayshobbies
The Thunder Powers would be great. I use the 3s 2100 with my BP20-15L and my new Himax.

Plus I sell them for $5-$10 less then the 4 venders above
Wow Clay! Great prices on the TP lipos. I just added a link to your site on mine. You'll be getting an order from me soon!

Tim H.

vw63 - I would go with the TP 3s 2100 pack. That's what I'll be running on my 40" Ultimate Bipe with a Hacker B20-15L, 10x4.7 or 11x3.8
Sep 24, 2003, 06:34 PM
Registered Snoozer
Neil Morse's Avatar
I've been flying my Switchback 3D with a B20-15L on 9 KAN950's with an APC 12X6 E prop with great success. I just bought my first Thunder Power 3S1P 2100 pack. I'm assuming I will have to prop down to avoid overheating the pack. What prop do people recommend? Thanks.

Sep 24, 2003, 07:18 PM
Tim H.'s Avatar
Static Analysis - 40" UB
Sea Level, 70F

Motor: Hacker B20 15L; 3704rpm/V; 0.064 Ohms; 0.7A idle.
Battery: TP 2100; 3 cells; 2100mAh @ 3.7V; 0.0033 Ohms/cell.
Speed Control: Castle Creations Phoenix 35; 0.0045 Ohms; High rate.
Drive System: APC 11-Inch Propellers; 10x3.8 to 11x4.7 (Pconst=1.11; Tconst=0.95) geared 4:1.
Airframe: 40" UB;; 17.5oz; 7.3oz/sq.ft; Cd=0.057; Cl=0.46; Clopt=0.65; Clmax=1.24.

NC Gear Diam Pitch Batt Motor Motor Input Output Loss Temp Motor Motor Elect Prop Thrust
..... Ratio (in) (in) Amps Amps Volts (W) (W) (W) (F) Ef(%) RPM Ef(%) RPM (oz)

3 4.00 10.0 3.8 13.1 13.1 10.9 142.9 122.7 20.2 155.5 85.9 36668 84.4 9167 27.0
3 4.00 10.0 4.7 15.2 15.2 10.9 165.9 140.3 25.6 178.6 84.6 35720 82.9 8930 28.9
3 4.00 11.0 3.8 17.1 17.1 10.9 185.1 153.7 31.4 203.2 83.0 34809 81.2 8702 34.9
3 4.00 11.0 4.7 19.3 19.3 10.8 209.3 168.2 41.1 244.3 80.3 33414 78.3 8354 36.6

I would try a 10x4.7 and an 11x4.7

Last edited by Tim H.; Sep 24, 2003 at 07:21 PM.
Sep 24, 2003, 07:42 PM
Registered Snoozer
Neil Morse's Avatar
Thanks, Tim. I will give those two choices a try and monitor my pack and motor temperatures carefully.

Sep 24, 2003, 09:11 PM
Registered User
Clayshobbies's Avatar
I use the APC 10x6 Slow Flyer with my TP 3s 2100, Hacker BP20-15L and the Himax 4.3:1.

Thanks Tim. Is everything on your site free?