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Old Apr 05, 2011, 11:45 PM
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3s vs 4s 2200mah difference

I am new to RC electric RC and have two planes, the PZ P-47 which takes a 3s 2200mah lipo and an Airfiled bf109 which came with a 4s 2200mah lipo. Apparently the bf109 can take batteries from 2-4s. My question is what is the difference between a 3s and a 4s lipo that has the same mah (2200 in this case) assuming the C rating was the same on both batteries (20C)

Would I get longer flight times with the 4s 14.8v battery than with the 11.1v 3s battery?
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Old Apr 05, 2011, 11:58 PM
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Quote:
Originally Posted by kcchiefdawg View Post
I am new to RC electric RC and have two planes, the PZ P-47 which takes a 3s 2200mah lipo and an Airfiled bf109 which came with a 4s 2200mah lipo. Apparently the bf109 can take batteries from 2-4s. My question is what is the difference between a 3s and a 4s lipo that has the same mah (2200 in this case) assuming the C rating was the same on both batteries (20C)

Would I get longer flight times with the 4s 14.8v battery than with the 11.1v 3s battery?
With throttle management flight time should be similar. Full throttle the current draw will be much higher don't go from 3s to 4s with out checking amp draws and probably propping down several sizes.
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Old Apr 06, 2011, 12:05 AM
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Does current draw translate into torque or power? I am not switching from a 2s to a 4s lipo in my bf109, it came with a 4s lipo. I am asking because I already have two other 2s lipos of the same mah so I was wondering what I would notice by using those 3s lipos or if it is a bad idea.
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Old Apr 06, 2011, 12:12 AM
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Originally Posted by kcchiefdawg View Post
Does current draw translate into torque or power? I am not switching from a 2s to a 4s lipo in my bf109, it came with a 4s lipo. I am asking because I already have two other 2s lipos of the same mah so I was wondering what I would notice by using those 3s lipos or if it is a bad idea.
If you go down in cell count there will be a decrease in power but it shouldn't hurt anything.

VoltsXamps=watts. Most people relate power out put to watts so

Say 12 volts X 20 amps = 240 watts for a 3s setup versus 16 volts X 20 amps = 320 watts for a 4s setup. Not a perfect example but it gets the point across.
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Old Apr 06, 2011, 12:17 AM
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ok so the plane will have less power but the flight time should be comparable to that of a 3s lipo with the same mah and C rating?
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Old Apr 06, 2011, 12:22 AM
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Thanks, I think I get the idea of it being more powerful, so my only remaining question is about the flight times. I am assuming that the flight times should be about the same with both batteries due to the mah being the same. Am I correct?
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Old Apr 06, 2011, 12:42 AM
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Thanks, I think I get the idea of it being more powerful, so my only remaining question is about the flight times. I am assuming that the flight times should be about the same with both batteries due to the mah being the same. Am I correct?
Flying the same flight yes it should be similar.
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Old Apr 06, 2011, 02:32 AM
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Originally Posted by kcchiefdawg View Post
... Apparently the bf109 can take batteries from 2-4s. My question is what is the difference between a 3s and a 4s lipo that has the same mah (2200 in this case) assuming the C rating was the same on both batteries (20C)

Would I get longer flight times with the 4s 14.8v battery than with the 11.1v 3s battery?
Power is measured in watts, and watts = volts x amps, so if you want the same power from a 4S battery as from the 3S, you'll have to reduce the amps. Provided you do that (by using a smaller prop), you will then get longer flight time from the same mAh because you're using less amps

But you must be careful when switching battery volts; even though the motor and ESC are designed for 2S to 4S (7.2v to 14.4v), it does not necessarily mean that you can just put a 4S pack into a model that's been set up for 3S or 2S. The number of volts and the prop size determine how many amps the motor will draw, and putting in more volts without reducing the prop size will usually burn up the motor and/or ESC -- unless the motor is running at only half it's potential power output on 2S.

If you give us a link to your model, maybe someone with hands-on experience of it can say what prop you need to use -- or maybe it's in the instructions somewhere.
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Old Apr 06, 2011, 09:13 AM
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Thanks!
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Old Apr 06, 2011, 01:27 PM
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Originally Posted by abenn View Post
Power is measured in watts, and watts = volts x amps, so if you want the same power from a 4S battery as from the 3S, you'll have to reduce the amps. Provided you do that (by using a smaller prop), you will then get longer flight time from the same mAh because you're using less amps

(snip)
Not quite correct. But the end result is the same ;-)

Watts = volts x amps. Even if you prop down to keep the power level the same (fewer amps) with the 4 cell, you must remember the volts are HIGHER.

Example: 11 volts x 20 amps = 220 watts
but: 14 volts x 15.7amps= 220 watts

You will get longer flight times with the 4 cell, but it is because of the extra cell. Think of a gas tank that holds 4 gallons instead of 3 gallons. In round easy to understand numbers, use the example of a 1000mah lipo pack. A 3 cell pack contains 11 volts x 1000mah = 11,000mah while a 4 cell pack contains 14 volts x 1000mah = 14,000mah.

How long you can fly depends on the mah (milliamperhours) contained in the battery divided by the mah used by the motor and equipment.


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Old Apr 06, 2011, 01:41 PM
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Originally Posted by cliffh View Post
... You will get longer flight times with the 4 cell, but it is because of the extra cell. Think of a gas tank that holds 4 gallons instead of 3 gallons. In round easy to understand numbers, use the example of a 1000mah lipo pack. A 3 cell pack contains 11 volts x 1000mah = 11,000mah while a 4 cell pack contains 14 volts x 1000mah = 14,000mah.

How long you can fly depends on the mah (milliamperhours) contained in the battery divided by the mah used by the motor and equipment.


Cliff
Another way to look at it, but you need to get the units right

Since volts x amps = watts, the units in your example need to be 11,000mWh and 14,000mWh (mWh is milliwatt-hours).
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Old Apr 06, 2011, 04:56 PM
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Another way to look at it, but you need to get the units right

Since volts x amps = watts, the units in your example need to be 11,000mWh and 14,000mWh (mWh is milliwatt-hours).
You are absolutely correct. It is milliwatt-hours.

Thanks for correcting me.

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Old Today, 02:04 AM
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Hi that information was really useful
but just to make sure as I'm a beginner in this field can u please tell me if I'm right or wrong in my new and first setup:

-hex-copter with 6 motors A/2212 /1000kv + 6 ESC 30A
-DJI Naza- Lite Flight controller
-10X45 propeller 1045
-Lion Power Lipo 14.8v 5200mah 30C - 40C 4S1P Battery 156A Continuous discharge
- FS+i6 Flysky 2.4-Ghz 6 channels RC Remote transmitter
- DJI 2 axis gimbal for go-pro hero 3

thanks for your advice
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