Regen braking: confirmed!

[jhautz]

This is cool Brian. I always wanted to do this test myself but never really had a good enough multimeter to do it. Especially after a little experiment I did myself a couple weeks ago. I have actually been meaning to start a thread on this very topic. I have heard for a long time that they did have regenerative braking in just about all ESCs but never saw any proof of the fact.



I'm hopeing someone can answer why it is that I see 10-15% better milage when I run mechanical brakes? This is on the same truck on the same day on the same track with the same setup and batteries. I did some testing the last time I went out for a practice day and wanted to see what effect the mechanical vs motor brakes had on run time. I ran 2 5 minute runs with the mechanical brakes on 2 different packs, and then took the mechanical brake off, and charged the packs back up recording the amount of energy I put back in each one. Then ran two 5 minute runs with the mechanical brakes taken off and used motor brakes. I tried to drive just as hard with both brake setups and ran 2 trials on each just to add a little extra data.

But for sure, both runs with the motor brakes used more mah from the packs than the runs with the mechanical brakes did.

A day or 2 after I actually did this I realized I could have used my eagle tree to get better data. Next time I will do it that way.



I just dont get it, the evidence would support the opposite effect being true. Longer run time with motor brakes.

Wondering if anyone has any thoughts?

[teknorc]

Originally Posted by jhautz

This is cool Brian. I always wanted to do this test myself but never really had a good enough multimeter to do it. Especially after a little experiment I did myself a couple weeks ago. I have actually been meaning to start a thread on this very topic. I have heard for a long time that they did have regenerative braking in just about all ESCs but never saw any proof of the fact.



I'm hopeing someone can answer why it is that I see 10-15% better milage when I run mechanical brakes? This is on the same truck on the same day on the same track with the same setup and batteries. I did some testing the last time I went out for a practice day and wanted to see what effect the mechanical vs motor brakes had on run time. I ran 2 5 minute runs with the mechanical brakes on 2 different packs, and then took the mechanical brake off, and charged the packs back up recording the amount of energy I put back in each one. Then ran two 5 minute runs with the mechanical brakes taken off and used motor brakes. I tried to drive just as hard with both brake setups and ran 2 trials on each just to add a little extra data.

But for sure, both runs with the motor brakes used more mah from the packs than the runs with the mechanical brakes did.

A day or 2 after I actually did this I realized I could have used my eagle tree to get better data. Next time I will do it that way.



I just dont get it, the evidence would support the opposite effect being true. Longer run time with motor brakes.

Wondering if anyone has any thoughts?

The motor is still using power to stop. In other words, ESC braking is not free. The 'regenerative' part is that it can recapture small (if not tiny) amounts of power in between the pulses while the braking power is applied. After all, a force is essentially being applied in the opposite direction to bring the car to a stop, just as it would if it was starting from a standstill. This is also why motor brake setups run hotter since the motor is working in both directions. Also, braking force is usually applied more abruptly than while accelerating. AFAIK, a single mechanism (the motor) can't function as a generator and a source of power at the same time. You must use power to brake the car. I'm not an electrical engineer, but I know a few things about physics and the forces that are present and being applied in this scenario simply can't be ignored.

Please correct me if I'm wrong here because our results coincide with jhautz and others that have found mechanical brakes to be more efficient. I'm not arguing that some energy isn't being harnessed or regenerated while braking, I'm saying that it does in fact use power to brake and that the overall net of the system is negative, not positive. Mechanical brakes are obviously using power as well (servo), but compare a servo's energy requirements to a 1/8th brushless motor's requirements and I think the picture becomes clearer.

[jhautz]

Thats what I was always thinking. I can see how coasting off power would actually spin the motor and make it act like a generator. That makes sense to me. But braking to me always seemed like it would take energy to offset the energy that the truck already had in its momentum.

[tom255]

Originally Posted by teknorc

The motor is still using power to stop. In other words, ESC braking is not free. The 'regenerative' part is that it can recapture small (if not tiny) amounts of power in between the pulses while the braking power is applied. After all, a force is essentially being applied in the opposite direction to bring the car to a stop, just as it would if it was starting from a standstill. This is also why motor brake setups run hotter since the motor is working in both directions. Also, braking force is usually applied more abruptly than while accelerating. AFAIK, a single mechanism (the motor) can't function as a generator and a source of power at the same time. You must use power to brake the car. I'm not an electrical engineer, but I know a few things about physics and the forces that are present and being applied in this scenario simply can't be ignored.

Please correct me if I'm wrong here because our results coincide with jhautz and others that have found mechanical brakes to be more efficient. I'm not arguing that some energy isn't being harnessed or regenerated while braking, I'm saying that it does in fact use power to brake and that the overall net of the system is negative, not positive. Mechanical brakes are obviously using power as well (servo), but compare a servo's energy requirements to a 1/8th brushless motor's requirements and I think the picture becomes clearer.

Actualy Its consume very little not more than couple amps! One guy in russian forum made tests about regenerative brakeng and he did not recorded any noticable power consumption its just shorting motor windings and power force applies through shorting Impulse lenght and opposite phase switching, power consume mostly for FET drivers, brains then braking. MGM, MMM, MM, Schulze, Quark B125. No one regenerated a power, all regenerated power goes for FET heating.

[teknorc]

Please don't misunderstand. I'm not saying that regenerating isn't happening while braking. There is stored energy in the vehicle to be recaptured. But unless the regeneration or conversion of the stored kinetic energy is 100% efficient, some other energy must be used to stop the car, especially if you are braking hard at high speed. If the conversion was 100% efficient we'd have a perpetual motion machine in our RC cars. Shorted motor resistance is one thing, but we all know how motor brakes can flip a car on it's lid. If shorting was that powerful you wouldn't be able to turn a brushless motor shaft by hand if all three wires were touching each other. This is why I think there is power being applied while braking.

Again, I'm not an electrical engineer, maybe at higher speeds, the shorting becomes more powerful and violent enough to flip the car, not sure. This still doesn't explain why a lot of people are experiencing better run times using mechanical brakes though. I'd like to know for sure from someone who can explain it as well. I've read up on full scale regenerative braking and they all have mechanical brakes to supplement the regenerative brakes for various reasons. One of the reasons cited was to more quickly bring the vehicle to a stop from higher speeds.

So, please, someone explain. If motor braking is indeed free, I have a couple things I want to try to get even more run time

[JERRY2KONE]

AFAIK, a single mechanism (the motor) can't function as a generator and a source of power at the same time. You must use power to brake the car. I'm not an electrical engineer, but I know a few things about physics and the forces that are present and being applied in this scenario simply can't be ignored.

During my 20 years in the Navy I have seen on a couple of occasions where I generator which normally puts out huge amounts of power was turned into a motor when the electrical power flow was reversed accidently. Due to the circuitry involved within the system it was not supposed to happen, but it did.

There is no way that electrical braking is accomplished without using some source of power. That's just a relitive impossibility. But as you stated Patric can probably explain this so we can all understand it.

[tom255]

Originally Posted by JERRY2KONE

AFAIK, a single mechanism (the motor) can't function as a generator and a source of power at the same time. You must use power to brake the car. I'm not an electrical engineer, but I know a few things about physics and the forces that are present and being applied in this scenario simply can't be ignored.

During my 20 years in the Navy I have seen on a couple of occasions where I generator which normally puts out huge amounts of power was turned into a motor when the electrical power flow was reversed accidently. Due to the circuitry involved within the system it was not supposed to happen, but it did.

There is no way that electrical braking is accomplished without using some source of power. That's just a relitive impossibility. But as you stated Patric can probably explain this so we can all understand it.

Why you cant brake without power, ofcourse you can by just shorting windings on motor or put some capacitance (capacitors) to windings thats it, maybe its not so effective. Maybe you cant change brake force without power source, somehow you just need change chorting impulse lengt and opposite phase switching, that basicaly any ESC do.

I will speak with guy who made a tests on ESC to check Ezrun 150A, does energy recuperation braking works there?

[tom255]

Originally Posted by tom255

Why you cant brake without power, ofcourse you can by just shorting windings on motor or put some capacitance (capacitors) to windings thats it, maybe its not so effective. Maybe you cant change brake force without power source, somehow you just need change chorting impulse lengt and opposite phase switching, that basicaly any ESC do.

I will speak with guy who made a tests on ESC to check Ezrun 150A, does energy recuperation braking works there?

Ok that guy made a test and still No true regen brakes in ezrun 150.
He made test device/stand. In one side motor spinning other motor which was he tried to brake. Yeah, he noticed regen spikes (Voltage and negativ current) but those spikes are realy short, impulse lenght was 0.002s-0.007s so no true regeneration there, just some spikes thats all.
Seems ezrun 80a make same spikes

[George16]

Originally Posted by JERRY2KONE

During my 20 years in the Navy I have seen on a couple of occasions where I generator which normally puts out huge amounts of power was turned into a motor when the electrical power flow was reversed accidently. Due to the circuitry involved within the system it was not supposed to happen, but it did.

The mighty A-gangers did it again .

We lost power to the whole ship during my last deployment due to this. We basically shorted the diesel generator.

Anyway, whatever happens, energy is not lost or destroyed (First Law). However, it is transformed into another form of energy which is basically heat. Now you wonder why motor braking produces a hotter motor compared to mech brakes .