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Old 07-18-2007, 08:32 PM   #16
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So why are people running 5 cell burning motors and dumping batteries?
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Old 07-18-2007, 08:46 PM   #17
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Originally Posted by BlueBird-sr View Post
So why are people running 5 cell burning motors and dumping batteries?
This paragraph basically explains it:
But now to get some of the power (speed) back, you might drop to a lower wind (less resistance) which will get more current to flow more easily. Basically what you are doing is increasing the ammount of Watts the motor displaces BACK to what a given motor of a higher wind would put out at 6 volts. Now this gets you back up to speed (given the weight of the car is identical 5 or 6 cells) but at the expense of runtime. This is because each cell has a finite ammount of wattage it can produce (represented as mwhr on the cells)

Plus to get the same overall speed the motor must be geared to a lower fdr (bigger pinion) which we all know decreases run time because the motor draws much more power at stall than at max unloaded RPM. Brushless motors are rated by the number of RPM they produce per volt. Its basically fixed. So, to get the same overall speed, you gear them up and use hotter motors. Both of these actions reduce runtime because of the increase in displaced wattage.
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Old 07-18-2007, 08:55 PM   #18
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So what you are saying is that 5 cell is hard on motors and batteries?
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Old 07-18-2007, 09:31 PM   #19
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I'm saying that running a 6 turn is harder on your batts and motor than running a 12 turn.

It doesn't matter if its 3 cells or 20.

Am I being to vague?

Two cars the exact same weight that are capable of reaching the same speed, where one is 5 cell and one is 6 cell will be more difficult on the 5 cell car. READ SAME WEIGHT.

Two cars SAME MOTOR but different weight will be easier on the 5 cell car. (easier on the batts AND motor with the LIGHTER 5 cell car). AND the lighter 5 cell will have longer run time, but it will not be as fast as the SAME motor in a heavier car with 6 cells.
Heavier due to extra weight of the added cell.

So, yes, if your 5 cell car weighs as much as a 6 cell car, its harder on your batts. And, if you expect your 5 cell car to have the same speed as a 6 cell car, its going to be hard on your batts.

Same thing if you raced a 4 cell 12'th scale against a 12'th scale that has 6 cells. If you wanted the 4 cell to even be close, you would have to gear it to the moon. (In a straight line race) But its harder on your motor, and will result in decreased run time due to the increased amp draw.
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Old 07-18-2007, 09:57 PM   #20
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Originally Posted by PitCrew View Post
I think you guys have it generally backwards....
Just for starters, think about 12 scale 4 cell. Same motors, but they run WAY longer. (I know part of it is drive train effeciency)

But, you do not put power INTO the motor. Its not getting FORCED in there. The motor DRAWS power because of its very low resistance.
When you are using higher voltage, the current can more easily flow across what resistance it has. Therefore, with higher voltages comes higher current (amps). This means that the total ammount of power (watts) is much higher at higher voltages. And not just because the voltage is increased, but the amperage goes up as well.

So, at lower voltages (5cell) the motor draws less amps (because it does have resistance). So with lower voltage, there is less excess current that gets turned into heat, and more of the available power goes into making motion. Since the capacity is the same (one cell to 10 cells with a 4200 mah pack is STILL 4200 mah!!!!!) the runtimes will be higher with a given motor.

But now to get some of the power (speed) back, you might drop to a lower wind (less resistance) which will get more current to flow more easily. Basically what you are doing is increasing the ammount of Watts the motor displaces BACK to what a given motor of a higher wind would put out at 6 volts. Now this gets you back up to speed (given the weight of the car is identical 5 or 6 cells) but at the expense of runtime. This is because each cell has a finite ammount of wattage it can produce (represented as mwhr on the cells)

So simply, same motor with 5 cells will have longer runtime than 6 cells, but will go slower if car is same weight.
Hotter motor with 5 cells will have less runtime than its higher wind counterpart at 6 cells to acheive the same speed at the same weight.


Have you ever run 5 cells? higher voltage systems are more efficeint than lower voltage systems. you are trying to move the same mass with less power, so the motor is going to draw MORE amps than with a 6 cell pack. dont believe me? go run a 6 cell pack till it dumps then run a 5 cell pack. betcha you get about 1-2 or so mins less runtime.
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Old 07-18-2007, 10:06 PM   #21
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LOL

I know.

Selective reading I guess.....

did you read this:
Two cars the exact same weight that are capable of reaching the same speed, where one is 5 cell and one is 6 cell will be more difficult on the 5 cell car. READ SAME WEIGHT.

But, it draws more amps only because it will have to be geared higher to acheive the same speed.

Keep reading what I am saying. If you run the voltage up higher, the amps also increase even under NO LOAD. Have you ever broke in your brushes on a pulsar or motor master??? Don't belive me, run the motor at 2 volts, and look at the AMPS. Then run the voltage up to 7 volts... Notice the AMP DRAW????????
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Old 07-19-2007, 02:07 AM   #22
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i havent had any runtime issues with 5 cells (3.5 motor)even with my old 3700's
What type of run time are you getting with 5 cells? I think this is where you and I differ. I guess because I am spoiled by Li-po, and you appear to be quite the proponent for 5 cell, I'm curious as to what type of run time are you getting with the 3.5. I know it allows for more careful and concise driving on the track, but what size track are we talking about? I know you will give me an honest answer without being overly biased.
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Old 07-19-2007, 07:05 AM   #23
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Originally Posted by bxpitbull View Post
What type of run time are you getting with 5 cells? I think this is where you and I differ. I guess because I am spoiled by Li-po, and you appear to be quite the proponent for 5 cell, I'm curious as to what type of run time are you getting with the 3.5. I know it allows for more careful and concise driving on the track, but what size track are we talking about? I know you will give me an honest answer without being overly biased.
with the 3700's and twith the 3.5 i get just over 5 1/2 minutes with the 4200's i can get 6 minutes easy
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Old 07-19-2007, 11:36 AM   #24
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Quote:
Originally Posted by PitCrew View Post
LOL

I know.

Selective reading I guess.....

did you read this:
Two cars the exact same weight that are capable of reaching the same speed, where one is 5 cell and one is 6 cell will be more difficult on the 5 cell car. READ SAME WEIGHT.

But, it draws more amps only because it will have to be geared higher to acheive the same speed.

Keep reading what I am saying. If you run the voltage up higher, the amps also increase even under NO LOAD. Have you ever broke in your brushes on a pulsar or motor master??? Don't belive me, run the motor at 2 volts, and look at the AMPS. Then run the voltage up to 7 volts... Notice the AMP DRAW????????
i did a test this afternoon. ran the motor (fantom CO27) at both 2v and 7.2v as you suggested, but i got diffrent results...
Attached Thumbnails
Which is Quicker 5 or 6 cell?-test1.jpg   Which is Quicker 5 or 6 cell?-test2.jpg  
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Old 07-19-2007, 11:50 AM   #25
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Is that a SILVERCAN?????

OK well you win.

So Why is it then that guys are melting stuff down at 5 volts rather than at six.

Go back and re-read my posts after you tell me why and you will see I have explained exactly why.

As far as my pulsar goes, mine starts at 2 volts, and usually shows around 7-8 amps for a stock motor (with no fan or anything). Then as I run the voltage up, the amp draw goes up. My better motors will cut the pulsar off.
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Old 07-19-2007, 01:32 PM   #26
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Originally Posted by PitCrew View Post
Is that a SILVERCAN?????

OK well you win.

So Why is it then that guys are melting stuff down at 5 volts rather than at six.
......
Who said that guys are melting stuff or have any kind of problems with 5 cells?

Only in certain occasions, i.e. very large open, high speed tracks, there might be problems making runtime, but overheating and equipment failure is defenetly a thing of the past.

Have you raced 5 cell brushless?
In Europe we 've been racing 5 cell brushless since November with great results and it seems that the rest of the world will follow our example.
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Old 07-19-2007, 02:22 PM   #27
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Originally Posted by Superkarter View Post
There is the same capacity in 5 vs 6 cell packs but because you can run things harder with 5 cell you use up more of that capacity
Incorrect. Each cell holds 4200mah. Adding a cell increases power capacity. For example If you wired them in parallel a 5cell pack would have 21000mah available with an output voltage ov 1.2v. A 6cell pack would have 25200mah at 1.2v. Since we wire in series, we see an increase in voltage not capacity, which is still an increase in available power.
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Old 07-19-2007, 04:44 PM   #28
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Originally Posted by John Doucakis View Post
Who said that guys are melting stuff or have any kind of problems with 5 cells?

Only in certain occasions, i.e. very large open, high speed tracks, there might be problems making runtime, but overheating and equipment failure is defenetly a thing of the past.

Have you raced 5 cell brushless?
In Europe we 've been racing 5 cell brushless since November with great results and it seems that the rest of the world will follow our example.
I didn't say that 5 cell stuff was melting down. Somebody else said it. I did see a speedo (5cell mod) go poof last weekend at Nats. I was paraphrasing a question with that sentence.

Looks like some people are getting what I am saying. That in order to make a 5 cell car as fast as a 6 cell car when they weigh the same, the 5 cell car must be run harder, ie...lower wind motor and taller gearing. This will decrease runtime.

However, for example if you ran 5 cell 19t with a lighter car vs 6 cell 19t with a heavier car, the 5 cell car will be slightly slower but it will have a longer run time. Unless it is geared really crazy or something.
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Old 07-19-2007, 05:57 PM   #29
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Speedo go poof all the time for no good reason...even in stock.
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Old 07-19-2007, 06:10 PM   #30
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Quote:
Originally Posted by PitCrew View Post
I didn't say that 5 cell stuff was melting down. Somebody else said it. I did see a speedo (5cell mod) go poof last weekend at Nats. I was paraphrasing a question with that sentence.

Looks like some people are getting what I am saying. That in order to make a 5 cell car as fast as a 6 cell car when they weigh the same, the 5 cell car must be run harder, ie...lower wind motor and taller gearing. This will decrease runtime.

However, for example if you ran 5 cell 19t with a lighter car vs 6 cell 19t with a heavier car, the 5 cell car will be slightly slower but it will have a longer run time. Unless it is geared really crazy or something.
have you run 5 cells?? I run 5 cells and you dont have to gear really crazy, only 2 or 3 teeth more on the pinion, i also ran 5 cells with the 10.5 at our last carpet race and it was pretty fast and my gearing wast too far off the 6 cell guys with the 10.5
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