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Old 07-18-2007, 03:22 PM   #1
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Default Which is Quicker 5 or 6 cell?

Can someone explain with technical info why 5 cell BL seems as quick as 6 cell? I know weight is part of the equation but it seems like a six cylinder car against a V8 is the same. 7.2v versus 6v? Surely more volts mean more power? More power quicker car and Longer runtime? Anyone??
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Old 07-18-2007, 03:28 PM   #2
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Less weight for the car to carry, especially in and out of the corners. When 5 cell cars enter the corners they carry less weight.

An eight cylinder car is heavy. A six cylinder car is lighter. It picks up to speed quicker but has less torque to keep the car upto speed. The infield is for the light car. The long straight is for the heavier car.

At Reedy Race this year, 5 and 6 cell cars cars were basicly putting in the same lap times.
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Old 07-18-2007, 03:28 PM   #3
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Can someone explain with technical info why 5 cell BL seems as quick as 6 cell? I know weight is part of the equation but it seems like a six cylinder car against a V8 is the same. 7.2v versus 6v? Surely more volts mean more power? More power quicker car and Longer runtime? Anyone??
5 cells doesn't seem faster, IT IS Faster than 6 cells

its easier to lay the power down,with less tire spin, tires last longer,motor and esc run cooler

you can gear up a little more than 6 cells
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Old 07-18-2007, 03:31 PM   #4
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Do you find a slower (less HP) car is EASIER to drive/handle then a much more HP car? In this case, we are not talking about Corolla vs Corvette. it is 6V vs 7.2V with the same BL motor system...only a little bit LESS HP, but you can push the existing car to its LIMIT....versus have more HP but you are fighting around the corner and TRY to keep your car in control.

Thats the different...

Don't forget, it is not drag racing...it is a road course. Every corner/turn counts...if you drive the best line, with the most speed, it will gives you the best lap time.........then keep that for 5 minutes, will equal to the best time. And in this case, may be a little bit LESS POWER car will give you the best time then a more horse power time.

Not to mention the extra 1 cell weight (not a lot) and a little bit less stress on your rubber tires.....those are the advantage of being 1 less cell.
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Old 07-18-2007, 03:35 PM   #5
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What about run time?? Can you still expect the same runtime with less power on tap?
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Old 07-18-2007, 03:35 PM   #6
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It's more like taking a formula ford chassis and dropping in an F1 engine and running it around Monaco. Sure it will be faster down the straight, but the Formula Ford engine will be much more driveable with the little tires and the tight confines of a track similar to what we run.

We moved from 7 cells to 6 in the early '90s in offroad for the same reason. We were just making too much power and we were spinning the tires. When we dropped a cell, it allowed us to move the power band higher up, not spin the tires off the corner, and go the same speed if not faster down the straight. Now offroad is close to dropping a cell again.
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Old 07-18-2007, 03:37 PM   #7
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What about run time?? Can you still expect the same runtime with less power on tap?
I believe you get a little more run time out of 6 cells.
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Old 07-18-2007, 03:49 PM   #8
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I believe you get a little more run time out of 6 cells.
I think its more that with 5 cells you use more powerful 3.5t brushless motors and gear them much higher. If you did this with 6 cell then you would probably dump just as bad, but you don't need to gear them as high with 6 cell because there is more voltage and power anyway.

So runtime is harder to make with 5 cell on larger tracks.
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Old 07-18-2007, 04:23 PM   #9
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I think its more that with 5 cells you use more powerful 3.5t brushless motors and gear them much higher. If you did this with 6 cell then you would probably dump just as bad, but you don't need to gear them as high with 6 cell because there is more voltage and power anyway.

So runtime is harder to make with 5 cell on larger tracks.
Runtime is harder to get because there is more energy stored in a 6 cell pack vs. a 5 cell.
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Old 07-18-2007, 04:27 PM   #10
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Originally Posted by Jack Smash
Runtime is harder to get because there is more energy stored in a 6 cell pack vs. a 5 cell.
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
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Old 07-18-2007, 06:23 PM   #11
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The amount of power our size of motors can put out is fixed. This is because the amount of heat that size of motor can dissipate is fixed. Try to put more power into the motor and you'll end up in temperatures where efficiency disappears (say 180degF and above).

5-cell or 6-cell, the power limit that the motor can handle is the same. 5-cell hits that limit at higher current, lower voltage, and with a motor with fewer turns of thicker wire (less internal resistance). 6-cell is the opposite.

5cell relative to 6cell:
same size motor --> same power limit
same power --> same speed on the track
slightly lower weight --> slightly better acceleration and deceleration and corner speed

However, as was just pointed out,
one less cell --> less energy in your battery
less energy in your battery --> dumping is easier to achieve
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Old 07-18-2007, 06:50 PM   #12
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The amount of power our size of motors can put out is fixed. This is because the amount of heat that size of motor can dissipate is fixed. Try to put more power into the motor and you'll end up in temperatures where efficiency disappears (say 180degF and above).

5-cell or 6-cell, the power limit that the motor can handle is the same. 5-cell hits that limit at higher current, lower voltage, and with a motor with fewer turns of thicker wire (less internal resistance). 6-cell is the opposite.

5cell relative to 6cell:
same size motor --> same power limit
same power --> same speed on the track
slightly lower weight --> slightly better acceleration and deceleration and corner speed

However, as was just pointed out,
one less cell --> less energy in your battery
less energy in your battery --> dumping is easier to achieve
i havent had any runtime issues with 5 cells (3.5 motor)even with my old 3700's
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Old 07-18-2007, 06:57 PM   #13
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You guys are getting too complicated. Here is is in a nut shell.

If you are drag racing in the street in front of your house 6 cell mod will be faster as it will have a highter top speed.

On a race track 5 cell mod is faster becuse it is more driveable and lets racers get around the track more quickly. 5 Cell faster becuse it allows racers to drive harder with more control. Top speed is not as important on the track...fast lap times are the key.
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Old 07-18-2007, 06:59 PM   #14
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You guys are getting too complicated. Here is is in a nut shell.

If you are drag racing in the street in front of your house 6 cell mod will be faster as it will have a highter top speed.

On a race track 5 cell mod is faster becuse it is more driveable and lets racers get around the track more quickly. 5 Cell faster becuse it allows racers to drive harder with more control. Top speed is not as important on the track...fast lap times are the key.
very well put Adrian

p.s. where are those pics??
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Old 07-18-2007, 07:12 PM   #15
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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.
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