5 cells? Why?

Old 05-29-2007, 12:02 PM
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Originally Posted by Advil
I wonder how fast a LIPO car could go if it only had to make the weight of a 5 cell car?????
You will see soon enough. Lipo is a sure thing now. It's not worth discussing 5 cell since the whole concept is stillborn.

At first we will run LiPo mixed with NiMh at NiMh weights. When LiPo takes over the weight will get dropped. Once NiMh is no longer used there is no sense in strapping an extra 160g to our cars for no reason.

The Stock and 19T clases will go a little faster at the lighter weight. Mod will go slower. The wheelspin on lighter cars will make it harder than ever for racers to make the jump from 19t to Mod.

I suspect 19T would be faster than Mod at most normal sized tracks.
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Old 05-29-2007, 12:10 PM
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I dont think we should keep the current weight with LiPo and build heavier cars, there won't be a need. The car will be lighter and therefore break less anyway.
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Old 05-29-2007, 12:10 PM
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Originally Posted by andsetinn
Actually the formula is: Less Voltage = More Runtime and Less Heat. Nothing retarded about that.
I forgot. Tsk tsk tsk, I must be getting old. Fewer cells = Less Weight. It means there is Less Weight to accelerate so you use less power to accelerate. It also means you accelerate comparably faster so the gap between 5 and 6 cells is smaller than you might think. It also means Less Weight to decelerate in crashes resulting in fewer broken parts.

Having said all this. I think 5 cell racing should be just another class in racing, not that it should replace 6 cell racing. I also think it would be better if LiPo and/or brushless would get seperate class to race in. Then we just wait couple of years and see which classes will die because of lack of racers. If they all have lot of racers, then everybody wins.
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Old 05-29-2007, 12:11 PM
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Originally Posted by AdrianM
You will see soon enough. Lipo is a sure thing now. It's not worth discussing 5 cell since the whole concept is stillborn.

At first we will run LiPo mixed with NiMh at NiMh weights. When LiPo takes over the weight will get dropped. Once NiMh is no longer used there is no sense in strapping an extra 160g to our cars for no reason.

The Stock and 19T clases will go a little faster at the lighter weight. Mod will go slower. The wheelspin on lighter cars will make it harder than ever for racers to make the jump from 19t to Mod.

I suspect 19T would be faster than Mod at most normal sized tracks.
Adrian, when lipo's do become the norm, how will this affect the chassis layouts?
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Old 05-29-2007, 12:33 PM
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Originally Posted by andsetinn
Actually the formula is: Less Voltage = More Runtime and Less Heat. Nothing retarded about that.

ACTUALLY higher voltage systems are more effieceint (read more runtime, less heat). 5 cell can be just as fast(in mod), but it puts a lot of strain on the cells since the motors are not as efficeint, and pull more amps.
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Old 05-29-2007, 12:37 PM
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Funny, I just picked up a Losi JRXS-R just to run lipo in (not built yet). I'm keeping my current TRF415 just to run the NiMh dinosaur cells, but want the simplicity of the Losi just for the balance issues associated with lipo. I tried my best to get the lipo balanced in the 415, but a orion 3200 weights in at 7oz, while my GP3700's are around 14-15oz mark. I had to add so much lead it looked like a boat anchor gone bad. As lipo does gain more approval manufactures will have to redesign there cars.......I'm sure they wont mind, some cars are replaced every 12 months anyway. Associated, Losi, and Schumacher are lipo friendly, but the losi is the one I consider the car layout of tommorow.
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Old 05-29-2007, 02:07 PM
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May as well break out my HPI Pro 3.5, that is li-po brick friendly. That was a stab at the Losi JRXS-R. Syndrome, simmer down boy.
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Old 05-29-2007, 05:48 PM
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Originally Posted by yyhayyim
Adrian, when lipo's do become the norm, how will this affect the chassis layouts?
Not much but the distribution of equipment will change. Lipos will get smaller and alloy for more room to put equipment on the right side of cars.
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Old 05-30-2007, 03:17 AM
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Originally Posted by geeunit1014
ACTUALLY higher voltage systems are more effieceint (read more runtime, less heat). 5 cell can be just as fast(in mod), but it puts a lot of strain on the cells since the motors are not as efficeint, and pull more amps.
Well, the Ohms law says Voltage=Current*Resistance. As you can see in this formula, using basic mathematics, less voltage equals less current. (It's much more complicated than that, but I'm not going to explain why resistance in motors changes with load, temperature and speed.) Trust me, this formula is valid.
Less current equals more runtime. You can look at the batteries as buckets full of electricity, if you empty them slower (with less current) then it takes longer for them to get empty. That, my friend, means more runtime.
You're right about efficiency of higher voltage systems. But, then you'd have to change the motors too .
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Old 05-30-2007, 05:37 AM
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Originally Posted by andsetinn
Well, the Ohms law says Voltage=Current*Resistance. As you can see in this formula, using basic mathematics, less voltage equals less current. (It's much more complicated than that, but I'm not going to explain why resistance in motors changes with load, temperature and speed.) Trust me, this formula is valid.
Less current equals more runtime. You can look at the batteries as buckets full of electricity, if you empty them slower (with less current) then it takes longer for them to get empty. That, my friend, means more runtime.
You're right about efficiency of higher voltage systems. But, then you'd have to change the motors too .


The number of times people say that lower voltage will mean more current draw drives me nuts.

To those who don't believe, run a motor on your motor checker and slowly turn the voltage down, the current will drop as well.

As Andsettin said, higher voltage systems are more efficient, but not if the motors are only designed and rated for 7.2V as they are now.

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Old 05-30-2007, 06:12 AM
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I happen to work on 240v and 480v electrical systems. Given both voltages are running electric motors, at say 1075 RPM, a typical 240v motor will draw maybe 1.5-2amps depending of the HP rating of the motor, while the same HP rated motor on 480v will draw 1 amp or less. I dont know the exact formula off the top of my head, but this is from 14yrs field experiance. So the more voltage you have does = less amperage draw. I know this based on commercial equipment, but the same will hold true for R/C systems of any type no matter the size of motor and voltages.
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Old 05-30-2007, 06:53 AM
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Originally Posted by hobbipro
I happen to work on 240v and 480v electrical systems. Given both voltages are running electric motors, at say 1075 RPM, a typical 240v motor will draw maybe 1.5-2amps depending of the HP rating of the motor, while the same HP rated motor on 480v will draw 1 amp or less. I dont know the exact formula off the top of my head, but this is from 14yrs field experiance. So the more voltage you have does = less amperage draw. I know this based on commercial equipment, but the same will hold true for R/C systems of any type no matter the size of motor and voltages.

But when going to fewer cells, the HP, or Watts, does not stay constant... This is how the motors pull less amps... Isn't electrical power = Voltage * Current? That would explain the drop in amps with a constant power rating for higher volts...
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Old 05-30-2007, 06:59 AM
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The above is true but if you put 480v into the 240v motor it will pull more current than the 240v motor at 240v. If we want to run higher voltages we need to change the motors to suit.
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Old 05-30-2007, 07:13 AM
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Originally Posted by Steve Weiss
I think another reason why 5 cell might be faster around the track is that you aren't getting the wheel spin that you do with 6 cell/lipo ...

It's akin to why 19T/stock guys can be just as fast if not faster through certain infeild sections than the mod guys are at times...

You're not spining tires...over shooting corners...etc...
Agree with you on that point and it makes total sense. I have noticed that even at IIC that some 19t guys are just as fast as Mod guys sometimes.
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Old 05-30-2007, 07:53 AM
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Guys,

If your argument behind five cell is becasue it is slower you coudn't be more wrong...Check out the video from the Reedy race and you will see some missles going down the back straightaway and faster lap times then LY!

Most of you guys who say that it is slower have never even tried it yet...on top of that you say it is "retarded" again without even trying it. Everyone wants to stay in their comfortzone and do the same thing and never try anything new...essentially operating in a bubble.

O wait I have something for you all of you!
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