Motor braking.

[GriffinRU]

I can explain to R&D engineer how it works and why, here we have other problems...

Post the Q and I will answer! But it is very difficult to explain how it works if there such big gaps in theory...

Bring, I am sorry but while your experiment is great, but the way how you explain what happen is really bad!

Do not treat it simple and do not make as complex as it looks..

[Serum]

Less resistance zero;

the lower the KV, the less resistance it has, and the less energy it produces when turning. The higher the KV, the less resistance it has, and the more energy it produces when it's turning.

I did sealed the motor with tape, both the front and the rear. (so the bearings etc. where well protected)

[GriffinRU]

Originally Posted by Serum

the lower the KV, the less resistance it has, and the less energy it produces when turning. The higher the KV, the less resistance it has, and the more energy it produces when it's turning.

Rene, this is very wrong. The same motor (independent of Kv) produce the same amount of power at given RPM, Efficiency is different...

I will be back later, need to go.

[zeropointbug]

Well, I don't want to seem superstitious or anything... but I think, I THINK there is a new thing out on the street, it's called inductance? :005:

[zeropointbug]

Originally Posted by GriffinRU

Rene, this is very wrong. The same motor (independent of Kv) produce the same amount of power at given RPM, Efficiency is different...

Yes, i agree

[Serum]

then what makes the different KV? it's not efficiency. internal resistance varies with different KV's and since some producers of motors give the KV value with the motor as a generator, i don't think your theory is right?

[Serum]

Sorry Artur; i meant internal resistance; not mechanical resistance..

[GriffinRU]

Originally Posted by Serum

then what makes the different KV? it's not efficiency. internal resistance varies with different KV's and since some producers of motors give the KV value with the motor as a generator, i don't think your theory is right?

Kv have nothing to do with resistance, it just happen that with more turns R goes up...
If you have motor 10 meters of copper wire goes through the magnetic flux but in one configuration you have single wire and in another double, the amount of power would be the same. One will have higher voltage another higher current...

Kv is complex number based on Magnet strength, gap, core properties, windings and much more, there are complicated programs dealing with how to calculate or estimate its value and most of them still black magic, in reality it is much easier to measure...

Now, definitely need to run :)
On braking part, there plenty BL motor control algorithms published on line, fined them check them. There is no other magic then shorting phases to stop the vehicle. And none of real R&D engineers will publish here unless he want to loose his job :)

[Serum]

Yeah, but i was talking about braking; this whole topic is about braking; so when i said that the motor of a lower kv produces less energy when turning; i meant that with the motor as a generator, and the energy it produces when the motor is turning, due to the inertia of the vehicle/moving mass. I guess i told it with too few words..

A lot of misunderstandings are going around here...

[zeropointbug]

higher numbers of turns, higher inductance, along with the core which it's wound on, and some other factors which may be out of control as far as manufacturer techniques that will probably effect efficiency as well as Kv.

[zeropointbug]

Originally Posted by Serum

A lot of misunderstandings are going around here...

I agree, you're not the only one. :005: :019:

[supralover72]

Would it be safe to use motor braking on a MM with 12 NiMh cells in a Jammin buggy with a fegiao 8xl and 14/46 gearing?

Thanks.

[BrianG]

Originally Posted by GriffinRU

...Bring, I am sorry but while your experiment is great, but the way how you explain what happen is really bad!

Do not treat it simple and do not make as complex as it looks..

Well, sometimes the answer is simple. I mean, if the FETs short the windings, how is that different than the experiment? The experiment would display the absolute most braking ability since there are no losses in other components since the windings were simply shorted, and there was no PWM action to reduce the effect. Please forgive the ignorance, but I am trying to learn the same as many people here.

[zeropointbug]

I agree with you Brian, that is the most it can do when shorted.

I think a better experiment would be to bring up to speed the wheels of a MT, and have motor connected with no ESC (motor is on motor mount). And then short them out and see how fast it slows it down. Keep in mind, it doesn't take much resistance further up in the drive train to slow things down wind (wheels).

The drill experiment shows lots of resistance, but that is a drill, and a drill only puts out more torque the slower it spins.... so it doesn't show us how fast it would slow it down. I'm thinking a flywheel experiment?

Artur, is there a diagram that you have, or COULD make that would show us exactly what is going on during braking in the FET; AND/OR when the voltage is high enough to charge batts?

[zeropointbug]

Just a thought, another way to brake an R/C car is to use alum. disc with neo magnet (disc type) and have a servo driven actuator to bring it into very close proximity to the disc. This creates tons of shaft resistance, and would not stress motor or anything. BUT, would not be super responsive as the servo would have to move it in and out. But would always work.