Mamba Pro - for all you tech-heads

[SpEEdyBL]

Originally Posted by Pdelcast

Careful, that's an assumption that may not be necessarily true. Just because the Kv of the motor is lower, doesn't mean that the current draw will be lower. Gearing has just as large an effect on current draw than Kv.

At a given voltage, and a given truck/car, it will still take the same number of watts to drive at a given speed -- and therefore the same current.

Patrick

Very true, but the 1900 i am refering to is effectively a 1512 1.5Y with twice as much resistance. Also, out of curiosity, I decided to gear the 1900 20/46 in my 8ight to match the theoretical top speed of the 2650 geared 14/46, and the 1900 was slower, was sort of sluggish, and ran cooler, meaning it used less power. Actually, I have noticed that the MMM heats up the most when using low throttle, i.e. racing on a track where the average speed is 15mph, vs. bashing out in the street or a grass field at 40 mph. With a 1900, i have to use more throttle input to get the same speed, causing the esc to run cooler as well. Those were just my experiences that led me to assume the 1900 on the MM Pro was ok. In fact, I don't even use the MMM fan with the 1900. I don't need it and the connector and solder joint to it broke off anyway. It's also a V2...

[Pdelcast]

Originally Posted by SpEEdyBL

Very true, but the 1900 i am refering to is effectively a 1512 1.5Y with twice as much resistance. Also, out of curiosity, I decided to gear the 1900 20/46 in my 8ight to match the theoretical top speed of the 2650 geared 14/46, and the 1900 was slower, was sort of sluggish, and ran cooler, meaning it used less power. Actually, I have noticed that the MMM heats up the most when using low throttle, i.e. racing on a track where the average speed is 15mph, vs. bashing out in the street or a grass field at 40 mph. With a 1900, i have to use more throttle input to get the same speed, causing the esc to run cooler as well. Those were just my experiences that led me to assume the 1900 on the MM Pro was ok. In fact, I don't even use the MMM fan with the 1900. I don't need it and the connector and solder joint to it broke off anyway. It's also a V2...

In most applications, yeah a 1512 1.5Y (1900) will draw less current because it generates more torque. But don't think it's the resistance -- a 1512 1.5Y is just as much a dead short from phase to phase as a 1512 1Y (2650...)

Resistance in these motors is so low that it doesn't have any significant effect on current draw.

[Pdelcast]

Originally Posted by SpEEdyBL

Very true, but the 1900 i am refering to is effectively a 1512 1.5Y with twice as much resistance.

You could make the resistance 50 times as much -- still wouldn't have any real effect on current draw.

You have to realize these motors will pull whatever current they need to produce the torque you ask of them.

A 1512/1.5Y has about 6.5 milliohms of resistance. With a 20 volt battery, the stall current is about 3100 amps.

A 1512/1Y (like the Castle 2650 motor) has about 4.5 milliohms of resistance. With a 20 volt battery, the stall current is about 4400 amps.


So you see, resistance doesn't matter ONE BIT. It's about torque generation -- which is gearing, tires, terrain, vehicle weight, etc.

The motor will draw whatever current it needs to generate the torque that is asked of it. A 1512/1.5Y when incorrectly geared can easily draw over 1000 amps.

All of these types of motors don't have enough resistance to have any real effect on current draw.

[BrianG]

Originally Posted by Pdelcast

You could make the resistance 50 times as much -- still wouldn't have any real effect on current draw.

You have to realize these motors will pull whatever current they need to produce the torque you ask of them.

A 1512/1.5Y has about 6.5 milliohms of resistance. With a 20 volt battery, the stall current is about 3100 amps.

A 1512/1Y (like the Castle 2650 motor) has about 4.5 milliohms of resistance. With a 20 volt battery, the stall current is about 4400 amps.


So you see, resistance doesn't matter ONE BIT. It's about torque generation -- which is gearing, tires, terrain, vehicle weight, etc.

The motor will draw whatever current it needs to generate the torque that is asked of it. A 1512/1.5Y when incorrectly geared can easily draw over 1000 amps.

All of these types of motors don't have enough resistance to have any real effect on current draw.

You should have a "newb" controller with a static 1 ohm resistor in series with each motor phase. Would help tame those current bursts, but not sure what adverse effect that would have on the ESC.

[Pdelcast]

Originally Posted by BrianG

You should have a "newb" controller with a static 1 ohm resistor in series with each motor phase. Would help tame those current bursts, but not sure what adverse effect that would have on the ESC.

We are planning to put a "newbie" mode in the next version of software -- where you can quickly program a "limited power" mode on power-up. This will limit output power to say, 50% of normal power.

I'm thinking that when I take out my electric Baja, I can run it in "normal mode", and then let my 8 year-old daughter take it out in "newbie" mode -- and I won't have to worry about it as much.

What do you guys think??

[muck]

Originally Posted by Pdelcast

We are planning to put a "newbie" mode in the next version of software -- where you can quickly program a "limited power" mode on power-up. This will limit output power to say, 50% of normal power.

I'm thinking that when I take out my electric Baja, I can run it in "normal mode", and then let my 8 year-old daughter take it out in "newbie" mode -- and I won't have to worry about it as much.

What do you guys think??

i like the idea, when i throw my daughter behind the remote, i will not have to cringe as hard.....

[BrianG]

Originally Posted by Pdelcast

We are planning to put a "newbie" mode in the next version of software -- where you can quickly program a "limited power" mode on power-up. This will limit output power to say, 50% of normal power.

I'm thinking that when I take out my electric Baja, I can run it in "normal mode", and then let my 8 year-old daughter take it out in "newbie" mode -- and I won't have to worry about it as much.

What do you guys think??

I like the idea. But, won't that be the same as simply turning down the throttle EPA on the radio? And your FAQ page specifically says not to do that. I can't think of any other way to programmatically accomplish what you are talking about. Personally, it would be easier to simply use less battery voltage and dial in 100% punch control.

Now, when you release your ESCs with data logging, you could use the current measurements to automatically dial in punch control and maybe even some EPA to keep current within reasonable limits.

[Pdelcast]

Originally Posted by BrianG

I like the idea. But, won't that be the same as simply turning down the throttle EPA on the radio? And your FAQ page specifically says not to do that. I can't think of any other way to programmatically accomplish what you are talking about. Personally, it would be easier to simply use less battery voltage and dial in 100% punch control.

Now, when you release your ESCs with data logging, you could use the current measurements to automatically dial in punch control and maybe even some EPA to keep current within reasonable limits.

The FAQ page says not to use the EPA because we don't want people setting up a system that draws, say, 400A at full throttle, and then using the EPA to limit current...

If currents are fine at full throttle (are within reason...) there's no reason why you couldn't use EPA to limit throttle levels.

Patrick