75A+ into 6384 150kv Motor??? No burning, right?

[absolutt1]

Hi, I'm an absolute beginner in the world of ebikes, so bear with me.

Can the BDUAV 6384 150kV motor handle 75A of current using Makerbase VESC 75100 v2 and 10s3p 21700 cells (5C, CDR: 25A, nominal current: 75A)? Also, will i have problems with the VESC, having a little of headroom (25A)?

The manufacturer of the motor claims to give 3280W with 24-36V, which should mean:
P = V * I
1) I = 3280 / 37
2) I = 3280 / 42
-> I = 78–88.6 A

So, that means it's safe to go 75A, right?

About the battery:
1) Should i also give it some headroom for CDR, like more than 105 A, and then limit it via BMS and VESC?
2) The motor's voltage should be 24-36V, meaning i should build a 9 series battery pack, right? 4.2V * 9 = 37.8 V

Any suggestions are appreciated.

 

[neptronix]

battery current or phase current?

Remember that VESCs and many other RC controllers are rated on a phase current basis instead of a battery current basis like ebike controllers are.

You probably want a 200A VESC.

As for the motor, look up a similarly dimensioned one and you could imply the current handling from another motor.

 

[absolutt1]

I read about it just now. It has been said by many that the phase current shall be 2-3 times the battery current, right?

As I understood, the max phase current is 100A for 75100. Meaning, the battery current has to be around 50A CDR. Then, I could set the phase current to say 75-80A in VESC tool. It would be working good, right?

As for the motor, yeah, it does seem to handle up to 90A, while i took a look at a similar 6385 motor that can supply 93A.

P.S. I can only stick to 75100 V2 right now.

 

[scianiac]

I think the controller choice will be fine in terms of current, it's quality may make it hard to tune as you push the current to the higher end but VESC generally performs well in general with this type of motor.

The more important factor is those motor power and current ratings are with a lot of cooling. You want to design the system first with a temperature sensor in the motor, not having one is just always a bad idea, and then to consider how you are cooling the motor vs how long it will spend at that current level. More cooling it can spend more time there, less cooling it can spend less time there.

Honestly these outrunner designs with enclosed bells seem kinda of pointless to me. Like the older aircraft style with vented bells, those you could seriously cool and yes dirt could get in but these sealed bells are anything but sealed, if you need a motor to resist water and dirt get an IPM motor. It's like the worst of all worlds which means you need to use a larger motor than you would with a vented bell to account for the inefficient cooling. Hence why e-skateboards often have 4 of these motors, and often larger versions of them either longer like 100s or larger class like 84 diameter.

Correction: Upon closer inspection the exact motor he listed does have vents, only on one side for some reason but it is certainly a lot better than many of the E-skate style motors I've seen.

 

[amberwolf]

Some thoughts:

Do you already know how much power it will take for the bike (?) to do the specific job you need it to do for you, under your specific riding conditions?

(we don't know what that job is, or any of your riding conditions, so we can't help you figure that out).

If you don't yet know any of that, you should first determine it so you can be sure the stuff you are planning on will do that job for you. (otherwise you may buy stuff, then find out it won't work the hard way, and have to buy more stuff).


You'll need to know the power levels anyway so that you can plan what battery to get to provide the power you need over the entire time (range) you need it for.


Additionally, most RC motors are designed to operate at high RPM wiht the propwash passing lots and lots of cooling air over them all the time, and to spin up very rapidly to their full loaded RPM. If you do'nt have these same conditions, the motor may heat up too quickly or else overheat over time, and may require special cooling to keep it doing what you want.

 

[absolutt1]

If you don't yet know any of that, you should first determine it so you can be sure the stuff you are planning on will do that job for you.

thank you for all given advice. Figured it out. Turns out I don't need that much current. 50-60A is plenty enough for reaching up to 45 kmh (28 mph). But, I have to look into the battery and phase current stuff. Still can't grasp much of them, though :|

 

[AdR]

Battery current is the actual DC current flowing out of the battery into the controller.
Phase current is the 3 phase current flowing out of the controller into the motor.
Phase current can be up to 2+ time the battery current depending on motor load.

 

[E-HP]

Can the BDUAV 6384 150kV motor handle 75A of current using Makerbase VESC 75100 v2 and 10s3p 21700 cells (5C, CDR: 25A, nominal current: 75A)? Also, will i have problems with the VESC, having a little of headroom (25A)?

So, that means it's safe to go 75A, right?

What do you mean by safe? Motors are rated under certain conditions. You could easily fry the motor or even one much bigger, if you give it 75A and the load is high enough to slow or stall the motor. At stall, all 75A is going straight to heat, since none of the power is going toward spinning the motor. So you, as the one in control of how you use the motor, are in control of whether the motor is abused to the point of failure. So, the motor can’t be made safe from you. If you describe how the motor will be used, then it can be determined if it is “safe” under those conditions, but we need to know what those are, as amberwolf alluded to above.

 

[scianiac]

As AW and E-HP pointed you operational conditions are key but I will reiterate buying a motor with a temp sensor or installing one makes it much much much harder to toast a motor, the controller with just keep turning the power down to keep it at the max temp you set. This is more important with small motors like these, on a massive hub motor you have so much thermal mass to heat it it's harder to cook it.

Additionally, most RC motors are designed to operate at high RPM wiht the propwash passing lots and lots of cooling air over them all the time, and to spin up very rapidly to their full loaded RPM. If you do'nt have these same conditions, the motor may heat up too quickly or else overheat over time, and may require special cooling to keep it doing what you want.

I'm just pointing this out to maybe add a little nugget to your knowledge base. A lot of these outrunner motors are now sold for E-skate which don't have active cooling and to make things worse they "battle harden" them by not including any vents which doesn't stop them from listing similar max power claims even though you can't forced air cool them well even if you wanted to. Just something to take into account when talking about these motors, they are not all created equal. Technically the one he listed does have vents, but only on one side which is weird.

And of course on an E-skate they are often not operating at high RPM. Which is not so say they are designed in any way to be better at doing that, they are still basically the same as the RC style, just worse. But it means you often have to overspec the motor a ton.