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 Electronics info 
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Post Electronics info
I posted this info on the forum once before.

This is just some info on Lipos and Brushless motors to help those coming into the hobby

Lipo batteries

each lipo cell has a nominal voltage of 3.7v so...

a 2s (2 cell) lipo is 7.4v
a 3s (3 cell) lipo is 11.1v
a 4s (4 cell) lipo is 14.8v
and so on...

the "C" rating is a constant multiplier and has no unit value. most companies will list two numbers, the lower one is the constant C rating and the higher is burst which should only be used for about 10 sec. I usually tell people to forget the burst and focus on constant C

why is it important?

lets say your running an castle mamba monster (abbreviated MMM) with a 2200kv motor. the 2200kv motor pulls about 120amps. if you have 4000mah 25c batteries, they will not provide enough amps

how its calculated
4000mah --> 4.0 amps
4.0amps x 25c = 100amps

as you can see if the motor pulls 120amps and your battery can provide only 100amps it is going to be too much for your batteries and they will overheat and puff

now if you got better batteries... say a 5000mah 30c
5000mah --> 5.0amps
5.0amps x 30c = 150amps

which will provide plenty of power and will stay cool after your run


now Kv v.s. number of turns

the number of turns is a more constant way of rating a motor b/c it is the number of times the coil is wrapped with wire and Kv rating will vary depending on manufacture.

to give an example

the Associated LRP Vector X-12 10.5 Turn Brushless Motor has a Kv rating of 3600Kv

the Novak SS10.5 Pro Brushless Electric Motor (discontinued) has a Kv rating of 4200Kv.

both are 10.5 turn motors but produce different Kv

this can be thought of as two muscle cars with 5 liter V8 engines going on the dyno, car A pulls 500hp and car B pulls 450hp, but each engine is made by a different manufacture and tested on different dynos.

Most of the time sensored motors will be rated by Turns and sensorless motors in Kv, why is this... i have no idea

Kv is a constant which is rpm per volt

if you have a 4600Kv motor and your running a 7.4v lipo battery the motor will produce 34,040rpm

how it is calculated
4600Kv x 7.4v = 34,040rpm
4600rpm/volt (rpm per volt) x 7.4v = 34,040rpm .... volts cancels out

after some research most motors will not survive running over 50k rpm for too long

sensored and sensorless

what the sensored is a sensor in the motor that detects exactly where the rotor is in relation to the can, the ESC processes the info and gives the motor the correct power to the correct wire. sensored systems are usually very smooth through out the power band. sensorless systems just have the 3 power wires which make these systems much less expensive.

now your probably thinking can you mix and match... yes and no

you can use a sensorless ESC with a sensored motor but your motor will cog pretty bad up to about 5mph or so, and sometimes coming out of corners.

only way to use a sensored ESC with a sensorless motor is if the ESC is capable. some senored ESCs will not put power to the motor unless the sensor cable is connected and some ESCs like the castle mamba pro (abbreviated mmp) and tekin RS/RS pro can run both sensored and sensorless motors

if you have questions or corrections just post them

hopes this helps you

Last edited by konaman on Sat Dec 04, 2010 6:28 pm, edited 1 time in total.

Wed Sep 15, 2010 9:06 pm
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Post Re: Electronics info
Outstanding post! A good candidate for sticky IMO.

Thu Sep 16, 2010 10:01 am

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Post Re: Electronics info
How should you store your Lipo batteries? Fully charged, fully discharged, or does it matter? Also do you hook up the balance wire every time you charge or is there a specific time to do it? I'm new to Lipos. Any help is appreciated.

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Fri Oct 29, 2010 7:52 am
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Post Re: Electronics info
I keep mine charged, and only balance them once every couple of months.

They're the only way to go.

Fri Oct 29, 2010 8:40 am
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Post Re: Electronics info
Do not ever discharge fully!! Store full charged and they do not like the cold!!

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Fri Oct 29, 2010 10:48 am
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Post Re: Electronics info
Hey man I gotta quick question. I hope you know the answer because Im stuck. I have a sc700 esc and Im having a problem setting it up. I have set up different esc's in the past but the instructions are either beyond me or maybe Im not catching on. Any help would be greatly appreciated. Thanks

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Thu Dec 13, 2012 6:58 pm

Joined: Mon Dec 27, 2010 10:51 am
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Post Re: Electronics info
How do I determine how many amps my motor will draw?

Thu Dec 20, 2012 10:19 am
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