How Regenerative Braking Works. 

Physicist, engineer, fabrication and design genius in one guy. Jeremy is an amazing guy and a superb teacher. Bravo!

As an engineer myself, the way you get excited about physics makes me happy.

Infinite energy machine confirmed.

Another excellent video Jeremy, and congrats on passing 1M subs! 👏👏👏 At 6:03 I think every engineer (inc me) remembers their eureka moment when they thought they could out smart the power companies and build some simple device that used gravity and magnets to build a perpetual motion machine instead of spending billions on a a complex nuclear reactor.

One thing I learned early on in my industrial maintenance career was how to check a permanent magnet DC motor to see if it was still good. First, you basically disconnect the power wires from the power source and make sure the shaft rotates relatively freely. (If it's a gear motor, you have to take into account the resistance of the gearbox) Then, you tie the two power wires on the motor together and try to turn the motor. If it is a good motor, the shaft won't turn without considerable torque being applied. It'll basically feel like the shaft is locked. If the motor still spins freely, more often than not, your brushes are totally shot out. It could also be that your armature is nasty as hell, or your rotor has some serious winding failure going on. Usually, it's the brushes are shot. If the motor still turns but is "grabby" in places and the bushes look good, then that's most likely a dirty armature.

Great video, as always. Clearly explained, and your excitement is infectious. You're truly one of the greatest educational channels for engineering.

I have been an industrial electrician for 20+ years. I have worked extensively with regen/dynamic braking. Mainly seen it used on the bigger cranes, and on large motors powered by VFDs. Instead of charging batteries, we dump the load through large resistors, producing heat. They are usually the component to fail

Wow love the explanation of how gravity itself is not energy, but a medium of storing it. That really helps make stuff like this more intuitive!

one of the top explainers on YT imho!

FYI: passenger electric rail cars use this dynamic braking, but use the heat energy to heat the passenger cab in the winter. The PATCO high speed line uses this (just in case this is not common). The dynamic braking is used from 60mph down to 5mph and only then the mechanical brakes engage. The mechanical brakes are far to jarring for the passengers otherwise.

Great Video as always. I get 20% plus back in regen braking in my 2014 Leaf. There was an app that showed owners all manner of data, including total energy used, energy from regen etc. The app no longer works, but there is still useful data in the car itself, such as Kilometers per Kilowatt Hour and real time energy usage or energy gain from braking. I can get a peak of 30KWH under braking and more sustained recovery of between 5-10 KWH at most stops or coasting downhill. I can drive in the city and barely touch the friction brakes, by leaving space to the vehicles in front of me, anticipating lights and traffic, and being less aggressive overall. At most stops, the regen slows me to around 10KPH. I am about to change the front brake pads for the first time and the rears were changed just last spring.

I love everything about this video. Your expanations along the way, your manufacturing skills, and your excitment is absolutely contagious. I've been in electrical engineering for over 2 decades now and watching this video has me as excited as my first day in the lab! Absolutely mint content. Thanks!

This video is absolutely fantastic. Not only did I learn a bit about a system I thought I understood fairly well, but it is always fantastic to find someone that has a passion and gets excited like this. I wish more people could find learning this exciting.

I'm glad you briefly touched on how trains use that same technology as they have been doing that for years. I've been in jobs where I rebuilt some of those dynamic grids and sent them back out to the railroad.

I upgraded the motor controller of my electric moped/scooter to one that supports regenerative braking(Kelly controller). I have also noticed that the faster you go, the harder the max generative breaking effect there is, and as you come to a stop, you may want to apply the normal brakes just a bit to fully stop the vehicle. A pro of regenerative braking that not many have talked about is the smoothness. The normal brakes on my electric scooter are very inconsistent, but this other system is very consistent. I think you should've added that pretty much all EVs use BLDC motors (3-phase), and not DC motors. I would be very interested in you explaining how they are able to use that braking on those motors, when you have exceed the voltage of the battery, and they still use the very same MOSFETs to do that as they use for spinning the motor. But great video!

I seldom have a use for any of the things you build, BUT I love absorbing the knowledge 🙂. I am (secretly ?) amazed that you can keep coming up with new lessons/projects. Thank you.

I'm a long time viewer and have seen your shop improvements over the years. Congrats on your cnc. Keep em coming!!

Congratulations on your 1 million subscribers! I am a big fan. We need more videos like this.

Wow - great video! It's an accessible, yet thorough explanation of regenerative braking. I recently got a hybrid vehicle and this explains so much! FWIW, 1:31 to 1:49, this is how guitar pickups work! Magnetic string vibrating near a coil of wire, generates a signal, which is then amplified by an... erm.... amplifier. It's wild that the same principle has so many applications.

One clarity I think you should make is that it's usable energy that changed. You always get exactly the same energy out as what put in. The losses we see are thermal losses. For example when the magnet is dropped down the tube there is also a very slight but present heating in the tube and magnet.

I really enjoy watching someone who obviously loves their topic 👏

Great video! As for applications, there are mining and logging operations out west that use either an electric train to bring coal down the mountain full to charge batteries to drive back up empty and also logging trucks that go down full of logs but can go back up empty. he only charge comes from braking against gravity. It saves so much money on fuel and on replacing brakes!

Great illustrations!! Love your positive vibe !! Congratulations on 1 million + subscribers!!!

Thanks for paying knowledge and development of intuitivity forward. Really appreciate it.

Glad to see you over 1M subscribers! Congratulations

Love the enthusiasm and the great demonstrations!

Wonderful job, young man! Your explanations are Clear and easy to comprehend.

Hydropower is energy from gravity, but it depends on the water already having potential energy, i.e. uphill from the turbine/generator.

Thank you for doing the experiment. Having the argument with people showed me that, just having equations and basic understanding of thermodynamics isn't enough to convince people. Some people just need to see it in action. Although some people will still think they know something everyone else don't.

My man doesnt set up a stand to hold the tube over the gopro. No, he effortlessly holds the tube exactly where it needs to be

Man, that "short circuit braking" is excellent 😂

You are such an amazing person to share all of your knowledge and you are so good at it

I have a 2016 Kia Soul EV, with a "93 mile range." During the summer, if I never drive over 40 mph, the car might report that, but realistically I get around 70 miles. This car has a "B" mode on the stalk, which is extra regenerative braking mode. I use this exclusively. The manual says I get around 12% back maximum, which tracks with the 10-20% you heard. I haven't done extensive testing because I just don't like driving in normal braking mode now. It's even at the point where I drive similarly in my (gas) work truck, rather than immediately applying the brake to slow down, I just let off the accelerator, until I need the brake. I took my EV to a Les Schwab not too long ago and they said my brake pads were like new, but my rotors had small rust spots, probably because I don't use them enough to get them hot.

Wish you were teaching physics back at Penn State!!!

I love to see you having so much fun. Great video, good man!

I love your joy, you are pleasant to listen to.

Man you’re a genius I aspire to be as intelligent as you bro 🙏🏾 thanks for the content

I bought a cable to hook into my Tesla Model 3's CAN bus, which lets you see data from the battery management system. It has lifetime energy meters for kWh charged by AC, charged by DC, and charged by regenerative braking. I was shocked to see that regenerative braking made up 23.7% of the total charge kWh.

My man, love your positive energy and of course your knowledge 🙏👑

Very good demonstration.

It is Bart Simpson riding his bicycle at night. He needs to use the headlamp, so he engages the generator. He now has light but he can barely pedal anymore. If he were coasting downhill the headlamp would shine and the bicycle would slow waaaay down.

Some large sailboats now have electric auxiliary drives instead of the usual diesel engine. Many of them can do "regenerative sailing", where the forward motion from the sails turns the propeller and generates power to recharge the batteries. (Sailboat propellers normally feather the blades when not in use, to reduce drag.)

Hi Jeremy, excellent video. Next, you should contact your local EUC community and get into electric unicycles 😀 where there are no physical brakes, everything is regenerative braking. Then, when you will be corrupted enough (riding EUCs is an incurable disease, once you get it, you cannot get rid of it, ever) you are welcome here (the other side of the mud globe) so we ride together. We supply the wheel and the beer.

When I drive my wife’s Prius I initially apply the brakes until the regen meter maxes out and continue to apply more break pressure to keep the meter maxed out until the meter drops even when more brake pressure is applied. Then I release the brake pedal as necessary to coast/manual brake to a stop. Usually this is on a freeway off-ramp. High current keeps the regenerative brakes from charging the battery because the battery will only accept current to a limit. Capacitors may be a way to increase short term high current flow, then release that energy quickly as you start to accelerate again. Just a thought

Thank you! Great info! I always learn something watching you.

As you mentioned at the end about disk brakes rusting without much use. A lot of car manufacturers are considering shifting back to drum brakes for EVs since braking demands are lower and the system is a bit more self contained which would reduce corrosion .

Absolutely love your explanations.

Love your work and teaching style. If I had teachers like you in school, I might have attended more. :)

🌴🌴🌴 Hi 👋🏼 Jeremy I Love the way your brain works. Thank you for another awesome video. Blessings,Carlos ✝️🙏❤️😊🇺🇸

Cool. With a bit of work the same set up can be used to show regenerative turning.

I am not bothered by the fact that I am unknown. I am bothered when I do not know others.

Thanks for sharing your knowledge Sir.

Thank you for a fantastic video on how regenerative braking works.

I cant wait until my kids are old enough to understand these concepts so i can share your videos with them and do some ove the demonstrations you present. Love your channel Jeremy. Excellent work!

This is the teacher Jeremy, which i begun to see years ago.

I love his laugh when the test proves the theory

I love this! Thanks for all your great content!

Jeremy, you are a national treasure.

I remember so many of the early projects! Never stop learning 😊

that ad break was perfect lol

Don't forget the larger weight of an electrical vehicle. The dynamic breaking is more necessary.

Don't have to add any "mechanical parts". You do likely have to add electronic parts, but it is worth it. Great video and physical examples.

You make science fun. This is the kind of stuff that make people love STEM. Great video.

I own a Toyota Yaris hybrid. It regenerates during braking, and it improves the range most when driving in the city, where you typically accelerate and brake many times. On a highway it doesn't help as much.

Great explanation, thank you.

Regenerative braking is very very helpful in mountainous areas where you can easily burn your disk brakes while going down.

" don't try this at home, I'm a professional, at least I look like one". Classic I love it. I'll have to remember that.

This is why I looked for a four wheel drive EV. They're heavier, but the disc brakes just don't give out. One thing I'd point out for efficiency is that for flat terrain the efficiency gain from regen brakes isn't too great, but soon as you get hills or mountains in there, the efficiency gain is huge.

Great video, wow you’re a top class engineer 🏴󠁧󠁢󠁥󠁮󠁧󠁿

I do enjoy listening to you explain things🙂 I've learned so much.

Edison Motors makes electric logging trucks. Since the trucks go up the mountain empty and come down with a full load, in some cases they get enough energy using regenerative braking with a full load coming down to the mountain to drive the truck back up the mountain.

We do use gravity to produce electricity. Hydro dams are a great example. We also do pumped hydro where we use excess electricity to pump water up a hill and then let it flow back down to produce electricity when needed.

Awesome video, thank you!

Living in Florida, I almost never touch the brake pedal in my Model 3. Regen is super cool tech.

18:55 even combustion engine cars. When the car is in gear, it shuts off the injectors to engine brake and the forward momentum of the car is converted to partly friction in the drive train and part of it ends up spinning the alternator.

Hey Jeremy, were you science oriented in your education? Engineering? Math? Physics? I'm so inspired by your understanding of these concepts and your ability to build so much. Thanks

You literally just made the concept of the powergrid click with your explanation

Enjoyed that one. From now on you should be known as Jeremy Electro-Magnetic Fielding :-)

A quick note on why it's hard to find data on how much regenerative braking increases your range... it's highly dependent on motor capacity, battery state (on average), and how often you start/ stop. While 48-volt (mild hybrid) systems are very efficient as far as resources, they just don't have as much capacity for energy flow or storage. Larger systems recover more energy but weigh more so they also require more energy. For freeway driving, the effects can be virtually zero, no matter the system.

I love his videos. They are so informative

My research considering how much percentage lost/gained is the route. If you are going mostly up hills and kinda coasting over them. I used a couple home made bikes on rural wv roads. I could easily regen 20% on a long circle. If you go the other way it took more to go up so like 5-6%. I also tested on a flat train path and got a similar result. Going slightly up gained 7% going back was getting like 10% because its mostly flat.

You know what's a fun thing engineers have to deal with in Hybrids and EVs: when you go from doing regen to slow the vehicle down to going backwards in reverse. The same force that is charging the battery and slowing you down can very quickly start discharging and send you the wrong way. Wonder if there is a way to show something like that in your setup.

Generator coil temperature is critical and by smell above what's sustainable and advisable for your EV. Good demonstration, the magnetic force is brutally converting into heat on the wire !

❤❤❤ that your dog likes to watch. I wish I could like and subscribe again. I love when ppl feature their animals in their videos. Thank you!

Been here since the 10K days glad to see you hit the Million mark and looking forward to two million.

Regen braking is very usefull in cases where you need to brake harder than coasting, due to trafic conditions. So I gues it depends on you're traffic situation and the driving style you maintain.

Super goood! Are you able to make a video breaking down that study you linked?! That would be interesting to hear your interpretation of it

WHEW! When you said lets get breaking, I thought Raygun was going to make an appearance. Glad that didn't happen.😂 In the salt belt, the regenerative breaking can often cause the disk brakes to rust to the point that they become nearly unusable. Maybe the newer ones have overcome this like you mentioned, but I've seen several hybrids with brakes that beome nearly useless after a long winter.

I have a Toyota Highlander hybrid that has 285,000 mi on it. I've only had to put one set of brakes on it in the time we've owned it. We also average about 28 mi to the gallon which is about 6 mi more per gallon than you would get with the standard model. The only issue I've run into is I have to be careful when I'm ordering parts because there are differences between the two models even in standard things like constant velocity joints.

It is probably worth mentioning that most ebike motors cannot do this. This is because of a one way clutch allowing it to power in one direction and coast in the other direction. If the clutch is removed or welded shut as found in a direct drive system, then you need to power the motor all the time or it will feel like a brake when you are not applying a throttle. Grin Technologies explores this and potential solutions in way more detail. On a properly built ebike system, they got about a 2-25% (average 10%) energy return and significant reduction in brake wear.

Many ev’s have brake disc rusting problems like audi e tron, mostly those use brake discs only when battery is full or when braking power must be higher than motor’s can produce

This is maybe the best/easiest way to demonstrate the concept even when considering AC motors, though you technically don't need two DC motors as you can just spin one with a flywheel under power, then switch over to neutral/coast (no power) and then braking (resistive load across windings). Of course how well that will work depends on how well the motor itself works as a generator. AFAIK something like a Tesla is not going to actually use a dynamo though. I could be wrong about that but I don't see why they would. Since Tesla's use AC motors they are basically using beefy inverters which allow dynamic braking by powering the field windings at a lower frequency than the shaft is rotating at the time, or below synchronous speed. An easy way for people to understand how that works is to imagine a VFD is spinning an induction motor at 30hz 1000rpm, then you input external force to the shaft to spin it at 2000rpm, and it's going to stop being a motor and become a generator. In that case the DC bus would be recharging and some kind of resistive load is necessary for switching it in to bleed excess power from overcharging the bus capacitors. The handy thing about a Tesla is that the main power source is actually DC just like the inverters themselves, so putting power back to the main supply is easy as just rectifying it (which is normally what happens in VFD's via reverse diodes built into the switches, essentially a 3p full bridge rectifier in reverse). When a VFD is using dynamic braking and turning the motor into a generator it isn't actually returning that power to the source (AC grid) unless it has a "regen" feature which then takes the stored DC power and inverts it back to AC to match the grid. With the huge DC battery there is no extra 'regen' inverter needed because it's already DC after it's rectified in reverse at the inverter outputs.

So, no "infinite power" today? Like you see in 90% of videos with 2 DC motors connected to each other :) Excellent explanation!

"Why don't we use gravity to produce energy"... we do, that's what hydroelectric power plants do.

This is a lovely video... I'm very impressed....

Simply the best! ❤

It would be cool to see a demonstration of how the regenerative braking is modulated. Not sure how that would be made quite as accessible as this since I gather it has a lot more to do with electronics than fundamental electromagnetics but if anyone can do it I'm sure it's Jeremy.

6:05 I can think of a few ways we do use gravity to generate electricity: hydro dams, regen braking downhill, gravity lights

There must be relative motion between the magnetic "field" and the wire. There are ways to alter the direction of the "field" without moving the magnets. All you need is an alternating "field" (N-S, S-N).

I miss the makin' shit outta old washing machines. It's what I subscribed for.