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Old 09-01-2016, 06:58 AM   #331
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What about LiFe 2s? :-P
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Old 09-01-2016, 11:35 AM   #332
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What about LiFe 2s? :-P
Size and capacity aren't there at the current time. If you could pack at least 3A into a typical 1/12th battery it would work.
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Old 09-01-2016, 11:49 AM   #333
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Given a fixed resistance, increasing the voltage will increase the current draw.
http://www.electricaltechnology.org/...creases_4.html

Your correct though, if your water pressure (volts) increases, then the amount of water flowed (amps)increases. Assuming the hose nozzle (resistance) doesn't change.

BUT, in electrical reality. If you lower the voltage, your load will draw more amps. So dropping from a 1s Lipo to a lower voltage 1s Life pack, should put more load on the ESC, if the motor can still pull it.

And generally in most cases, if my load only draws 2500 watts. And I can choose different motors or resistors to meet that wattage requirement (true work). Higher voltage will offer lower amp draws.
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Old 09-01-2016, 11:56 AM   #334
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If you're still running a 3.5 with a higher voltage, it will draw a higher amperage. But a 3.5 drawing more amperage on a higher voltage, is going to dyno much more wattage than it would on less voltage.

So naturally you'd drop down to a 6.5 motor that could produce the same power/wattage at the higher voltage. And much lower amp draw for the same amount of true power output.

It's easier to figure with pure resistive loads. A 2500w 480v heater draws less amps than a 2500w 208v heater.
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Old 09-01-2016, 12:34 PM   #335
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We could continue the Electrical Technology 101 discussion, but I think we're missing the point. There are 2 things I'm confident we're not going to do:

We're not going 2s
We're not going LiFe
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Old 09-01-2016, 01:10 PM   #336
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Exactly, we're stuck with 1s.
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Old 09-01-2016, 01:14 PM   #337
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The point is long gone or we wouldn't be talk about saving 1/12th

RANT
If 99% of the racing community feels 1/12th MOD is too fast it's not on straight speed, if it was a minimum rollout would all but eliminate that.
See bellow what I see as the culprits of decline:
-In almost every other electric class one battery is enough for a race day, not 1/12th when you are close to dumping all the time and the turnouts are what they are;
-price of electronics, availability of 1s batteries and other classes they could be run;
-current pace of chassis design development is too fast and too many options. Aluminium chassis, longitudinal or transversal battery placement, flex, no flex, wide, narrow... It's a pan car! It's supposed to be simple, if it is not simple then accept that only a handful of drivers worldwide can run them. Required know-how is inversely proportional to people driving the mentioned class, it happened with 1/8th on road, happens with 1/10th TC MOD and the others. Off road is stable because the requirements are lower.

The whole formula for 1/12th is wrong from the beginning, who thought about decreasing voltage when capacity increased? Were we supposed to run 1.0v when the capacity reached 10A?
/RANT
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Old 09-02-2016, 05:14 PM   #338
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Quote:
Originally Posted by Zerodefect View Post
http://www.electricaltechnology.org/...creases_4.html

Your correct though, if your water pressure (volts) increases, then the amount of water flowed (amps)increases. Assuming the hose nozzle (resistance) doesn't change.

BUT, in electrical reality. If you lower the voltage, your load will draw more amps. So dropping from a 1s Lipo to a lower voltage 1s Life pack, should put more load on the ESC, if the motor can still pull it.

And generally in most cases, if my load only draws 2500 watts. And I can choose different motors or resistors to meet that wattage requirement (true work). Higher voltage will offer lower amp draws.
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Originally Posted by Zerodefect View Post
If you're still running a 3.5 with a higher voltage, it will draw a higher amperage. But a 3.5 drawing more amperage on a higher voltage, is going to dyno much more wattage than it would on less voltage.

So naturally you'd drop down to a 6.5 motor that could produce the same power/wattage at the higher voltage. And much lower amp draw for the same amount of true power output.

It's easier to figure with pure resistive loads. A 2500w 480v heater draws less amps than a 2500w 208v heater.
The theories stack up with older brushed motors, double the voltage, which in turn doubles the current, producing quadruple the power.
But brushless DC motors don't seem to work like that.
If you lower the voltage the motor wants to pull more current to compensate.
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Old 09-03-2016, 12:33 AM   #339
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Originally Posted by Skiddins View Post
The theories stack up with older brushed motors, double the voltage, which in turn doubles the current, producing quadruple the power.
But brushless DC motors don't seem to work like that.
If you lower the voltage the motor wants to pull more current to compensate.
I paid money to learn electromagnetism physics and this is just not true.
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Old 09-03-2016, 04:26 PM   #340
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I paid money to learn electromagnetism physics and this is just not true.
So what is the effect on power of a brushless DC motor if you increase or decrease the voltage?
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Old 09-03-2016, 05:59 PM   #341
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Originally Posted by Skiddins View Post
So what is the effect on power of a brushless DC motor if you increase or decrease the voltage?
Short version, halving the voltage means 1/4 the power, and 1/2 the amp draw at zero RPM max torque, and 1/2 the peak RPM.

Long version:

There is no such thing as a DC brushless motor. Our brushless motors are three phase, permanent magnet motors, or permanent-magnet AC (PMAC) motors. The reason we use these for RC racing is that they can provide power very smoothly, unlike an AC induction motor which is the workhorse AC motor for everything from your clothes washing machine to a streetcar.

Even though it may be difficult to explain the inner workings entirely, what we call a "Brushless Motor ESC" would more accurately be called a "variable-frequency, hall-effect sensor-triggered, DC to 3-phase PMAC motor power supply."

In spite of these being, at least at a glance, more complex than non-induction brushed motors, the operating principles and forces are exactly the same. Zero-RPM peak torque (and peak amp draw at 0 RPM) can be calculated from internal resistance, ideal zero-load free-spin RPM calculated from resistance and strength of the internal permanent magnet rotor, and amp draw at any RPM is ideally a perfect linear correlation between your peak amp draw at zero RPM and your max free-spin RPM. With locked timing we can slightly "trick" the motor into upping the power output at the expensive of efficiency, but the power curve will still follow these rules.

Power = Volts * Amps.

Amps = Volts / Internal Resistance.

Therefore Power = ((Voltage)^2) / Internal Resistance

The only way to make a motor (in operation) increase its amp draw following a drop in input voltage is to hold the motor much closer to its stall speed.
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Old 09-03-2016, 10:02 PM   #342
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Quote:
Originally Posted by Skiddins View Post
The theories stack up with older brushed motors, double the voltage, which in turn doubles the current, producing quadruple the power.
But brushless DC motors don't seem to work like that.
If you lower the voltage the motor wants to pull more current to compensate.
Yes, exactly.
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Old 09-08-2016, 09:39 PM   #343
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Default Vegas 6.5

Hearing Vegas will be 6.5 .... Any thoughts
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Old 09-08-2016, 09:41 PM   #344
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Hearing Vegas will be 6.5 .... Any thoughts
Wish I had time to go this year ....
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Old 09-09-2016, 02:28 AM   #345
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Hearing Vegas will be 6.5 .... Any thoughts
Same guy who would have won with a 3.5 will probably win with a 6.5. Those are my thoughts.
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