Thread: Mamba Max 7700v
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DRIFT_BUGGY
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Posts: 2,077
Join Date: May 2007
Location: Australia
03.24.2008, 05:00 PM

In internal and beta testing, we were unable to find gearing options that would actually thermal the controller when used within spec:
Max input voltage for ESC: 3s lipo or 12 cell NiMH/NiCah
5700Kv motor max voltage: 3s
7700Kv motor max voltage: 2s

The Kv of a motor is the number of rpm’s it will turn per volt of input. So the 4600Kv motor will turn 4,600 rpm per volt of battery. On a 6 cell pack we can presume good cells are holding around 1v per cell, so 6v x 4600Kv = 27,600 motor rpm.

On the other hand, if we take a 3 cell lipo pack with the 7700Kv motor, that gives us 10.5v x 7700Kv = 80,850 motor rpm which is safe for the ESC, but well over the safe motor rpm limit so it cannot be used either.

So how can you get the most speed? You might think the 7700Kv motor having the highest Kv would automatically allow you to have the fastest setup right? Let’s find out:

7700Kv x 2 cell lipo voltage (max with this motor) = 53,900 motor rpm.
5700Kv x 3 cell lipo voltage (max for the motor and ESC) = 59,800 motor rpm

So the fastest 5700Kv motor setup is actually 6,000 motor rpm faster than the fastest allowable 7700Kv motor setup!

Now if you are racing with 6 cell packs only, then obviously the 7700Kv motor will be the fastest option for you, but we are routinely asked “what is the absolute fastest setup for my car/truck?” The answer in this case, is the 5700Kv motor with a high quality and high output 3 cell lipo pack made for 10th scale cars.
   
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