Mamba Pro - for all you tech-heads - Page 31 - RC-Monster Forums

SpEEdyBL · 10.16.2009, 08:37 PM

Quote:

Originally Posted by Cain

So, for a guy running 4S 1/8 buggy with say a Tekin 1900Kv motor, is this unit going to be suitable?

The 1900 draws 2/3 the current as the Castle 2650, I have done eagletree graphs on both. By my math, if the the MMM can handle the 2650, and the MMP is cable of 2/3 the current, the MMP should handle the 1900 just fine.

Pdelcast · 10.17.2009, 12:25 AM

Quote:

Originally Posted by SpEEdyBL

The 1900 draws 2/3 the current as the Castle 2650, I have done eagletree graphs on both. By my math, if the the MMM can handle the 2650, and the MMP is cable of 2/3 the current, the MMP should handle the 1900 just fine.

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

Unsullied_Spy · 10.17.2009, 05:26 AM

Is it a bad idea to run the CC 2650 on the MMP? I have 2 Hyper 7s and both are in need of ESCs and I'd like to try out the Pro, but the 2650 is going into my offroad basher and the Medusa is geared up to the point that it gets my MGM hot.

ravin · 08:29 AM

Quote:

Originally Posted by Unsullied_Spy

Is it a bad idea to run the CC 2650 on the MMP? I have 2 Hyper 7s and both are in need of ESCs and I'd like to try out the Pro, but the 2650 is going into my offroad basher and the Medusa is geared up to the point that it gets my MGM hot.

I was thinking of the same setup in a slash 4x4 on 4s.The slash is suppose to be about 1/2 the weight of a E-REVO .... (geared for low 40's).

Unsullied_Spy · 10.17.2009, 08:47 AM

In the Slash it should be fine because it's so light. I'm a bit worried about running one in my Hyper because it's rather heavy.

bdebde · 10.17.2009, 01:49 PM

If your MGM is getting hot, it would be a step backwards to go with the MMP; you need the MMM or add the fans to the MGM.

Unsullied_Spy · 10.17.2009, 06:13 PM

Quote:

Originally Posted by bdebde

If your MGM is getting hot, it would be a step backwards to go with the MMP; you need the MMM or add the fans to the MGM.

That's in my over-geared onroader, I'm thinking about my offroader but worried that the 2650 may be more than the MMP can handle.

kazuaki · 10.17.2009, 06:35 PM

Happiness...

SpEEdyBL · 12:42 AM

Quote:

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...

suicideneil · 10.18.2009, 10:48 AM

The esc heating up more with only partial throttle use is normal- the esc has to work harder (higher switching rate) making it less efficient- full throttle is when the esc is most happy and runs cooler.. its like a sign

Pdelcast · 10.18.2009, 01:42 PM

Quote:

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.

suicideneil · 10.18.2009, 07:57 PM

Unrelated Q for you Patrick:

Will the MMM v6 be using the same Fets as the MMPro, and have the adjustable BEC feature, maybe even the data logging feature too? If so, maybe it should be called the MMMPro?..

Another thought before I got to bed (1am here), assuming you do stick the car software/firmware into one of your ICE escs later down the line to make a HV car esc as such, would you be calling it the ICE Monster or the B.F. ESC as discussed a long time ago when a HV MMM was being wished for?

I do believe that either option would be rather cool...

Pdelcast · 10.19.2009, 12:39 PM

Quote:

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.

Pdelcast · 10.19.2009, 12:41 PM

Quote:

Originally Posted by suicideneil

Unrelated Q for you Patrick:

Will the MMM v6 be using the same Fets as the MMPro, and have the adjustable BEC feature, maybe even the data logging feature too? If so, maybe it should be called the MMMPro?..

Another thought before I got to bed (1am here), assuming you do stick the car software/firmware into one of your ICE escs later down the line to make a HV car esc as such, would you be calling it the ICE Monster or the B.F. ESC as discussed a long time ago when a HV MMM was being wished for?

I do believe that either option would be rather cool...

I can't comment on the feature set of the V6. Sorry...

We don't have plans (yet) to release the ICE as a strictly car version. We are talking about it though...

BrianG · 10.19.2009, 04:23 PM

Quote:

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.