Page 1 of 2

Implementing regenerative braking on electric longboard

Posted: May 31 2014 9:07am
by Daggers
I'm thinking of building an electric longboard and want to use regenerative braking but how would that be achieved? My knowledge of electronics is pretty low but I learn fast and can follow instructions pretty well.

Re: Implementing regenerative braking on electric longboard

Posted: May 31 2014 9:24am
by beto_pty
I think regen braking is more a promotional idea than anything else.. I brake perhaps 6-12 times an hour (actually tried counting it once) for a couple seconds each time, i coast a lot though...
So with a 100% efficient braking system i'd be regaining 20-40 seconds of runtime over the course of an hour..Assuming regen is not 100% efficient but say 50% (or 25% ) efficient the numbers dwindle into the tens of seconds per hour...

Disclaimer: live in a flat place..

unless you are longboarding down the alps I cannot see the cost/weight/complexity tradeoff being interesting

Re: Implementing regenerative braking on electric longboard

Posted: May 31 2014 9:25am
by Daggers
Ok, thanks! I live in a flat place too (florida) lol so I guess it wouldn't really be too helpful

Re: Implementing regenerative braking on electric longboard

Posted: Jun 01 2014 3:17pm
by torqueboards
I agree with beto. It's not even enough to be worth any value.

Re: Implementing regenerative braking on electric longboard

Posted: Jun 01 2014 3:25pm
by furp
Well, it would be nice to know how efficient it would be, how much % of the power that would be needed to drive the motor is regenerated when it spins free. in another topic, we came to the conclusion that regen 'braking' can not really works, since braking is reversed current and therefor needs power. However, if the motor is turned by riding down a hill without throttle, it generates a little power, would just be nice to know how much.

Re: Implementing regenerative braking on electric longboard

Posted: Jun 01 2014 3:38pm
by torqueboards
furp wrote:Well, it would be nice to know how efficient it would be, how much % of the power that would be needed to drive the motor is regenerated when it spins free. in another topic, we came to the conclusion that regen 'braking' can not really works, since braking is reversed current and therefor needs power. However, if the motor is turned by riding down a hill without throttle, it generates a little power, would just be nice to know how much.
beetbocks mentioned before. Can't remember though it was something like 3% or maybe even less.

Re: Implementing regenerative braking on electric longboard

Posted: Jun 01 2014 3:45pm
by furp
Ah, ok. I thought that the motor would be at least a little more efficient than 3% as a generator, but then again I have no clue . Well, assuming you use your eboard to go up a slope and ride it down freewheeling, you might get one extra run depending on your setup, but for everything else its not worth the hassle.

Re: Implementing regenerative braking on electric longboard

Posted: Jun 02 2014 3:46am
by Murfix
As furp said, it's actually regen coasting instead of regen braking. When the motor is forced to spin (ie. coasting) it acts as a generator. We coast a lot so we can regen a lot.

The esc has to be able to send the current in the opposite direction and you can only store the amount of current into your battery that is defined by the C-rate for charging of your pack. There's also some losses to be taken into account, mainly in the ESC, because all the power that it uses (switching and stuff) has to come from the generator instead of the battery.

Short: you need a special ESC and the higher the charging C-rate, the more efficient (up to a certain point).

Re: Implementing regenerative braking on electric longboard

Posted: Jun 02 2014 10:07am
by torqueboards
Murfix wrote:As furp said, it's actually regen coasting instead of regen braking. When the motor is forced to spin (ie. coasting) it acts as a generator. We coast a lot so we can regen a lot.

The esc has to be able to send the current in the opposite direction and you can only store the amount of current into your battery that is defined by the C-rate for charging of your pack. There's also some losses to be taken into account, mainly in the ESC, because all the power that it uses (switching and stuff) has to come from the generator instead of the battery.

Short: you need a special ESC and the higher the charging C-rate, the more efficient (up to a certain point).
Great explanation! Thanks.

Re: Implementing regenerative braking on electric longboard

Posted: Jun 02 2014 6:53pm
by Hummina Shadeeba
The tesla is getting. 64% from battery to road back to battery

:
How much energy does it recover?


Unfortunately, the adage “your mileage may vary” applies to regen as well. The amount of energy you can recover depends on how and where you drive. From the powertrain point of view it looks pretty good. The energy conversion efficiencies from chemical to electrical (battery), DC current to AC current (inverter), electrical to mechanical (motor), and torque to force (transmission and wheels) are all quite high and work just as efficiently returning energy into the battery. The bigger problem is aerodynamic losses and higher speeds and rolling friction of the tires. These both act to slow the car, but the energy dissipated cannot be recovered. We must also remember that, even though the battery-to-wheel conversion efficiency is pretty good (up to 80% or so), the energy makes a full circle back into the battery and it gets converted twice for a net efficiency of at most 80% * 80% = 64%.

Pretty awesome

Re: Implementing regenerative braking on electric longboard

Posted: Jun 03 2014 8:59pm
by beto_pty
I dont think so...
Acording to the law of conservation of energy(I think it's that one) and the imposibility of perpetual motion we find that coasting is basically inertia rolling our board... if we have bad bearings, spongy wheels, bad terrain or a generator strapped under our feet the distance will diminish.. requiring us to restart our motor earlier. Regen cannot posibly be 65%, my chargers get way too hot for that to happen..lets give it a best case scenario (up from beetbocks 3%) to lets just say an easy to calculate 20%... it would still mean that for every 100 feet of non coasting distance you would get 20 feet riding distance. Your net gain in this example is negative 80 feet...
ONly breaking counts as real regen...
movement and energy generation is not (as of this writing :D ) ...free..

Re: Implementing regenerative braking on electric longboard

Posted: Jun 03 2014 9:20pm
by Hummina Shadeeba
I think tesla was saying their energy retrieved from braking was their source of regen...which makes sense...as you were saying coasting wouldn't make sense as a source of regen because you'd just end up not really coasting as much. If regen were hooked up to the brakes then it make sense..but how is that possible for the tesla when we, on boards, use energy to brake if I'm not mistaken

Re: Implementing regenerative braking on electric longboard

Posted: Jun 04 2014 1:41am
by Murfix
I have to revise my statement. It was wrong.

A generator supplies power when an electrical load is connected.

Normal braking is applying an electrical load by the ESC. The generated power can't be used so it has to be dissipated into heat. that's why braking is tough on ESC's.
When regen braking, the electrical load is the energy stored into the battery (+ losses). The more energy you are storing, the stronger the braking will be.

Coasting is having a generator with no electrical load attached, so no useful energy is supplied by it. There's only the energy required to overcome the mechanical load of spinning the generator.

So it IS regen braking and NOT regen coasting.

Re: Implementing regenerative braking on electric longboard

Posted: Jun 04 2014 2:00am
by Hummina Shadeeba
[quote="Murfix"]I have to revise my statement. It was wrong.

A generator supplies power when an electrical load is connected.

Normal braking is applying an electrical load by the ESC. The generated power can't be used so it has to be dissipated into heat. that's why braking is tough on ESC's.
When regen braking, the electrical load is the energy stored into the battery (+ losses). The more energy you are storing, the stronger the braking will be.

Coasting is having a generator with no electrical load attached, so no useful energy is supplied by it. There's only the energy required to overcome the mechanical load of spinning the generator.

So it IS regen braking and NOT regen coasting.[/

How would brakes work without regen? I imagine they'd have to use power to brake. You'd put electricity to the motor but timing it to counter it's movement. So if we supposedly have regen is it using energy or retrieving it... Or starting to retrieve at low levels but using energy when braking hard?

Re: Implementing regenerative braking on electric longboard

Posted: Jun 04 2014 4:13am
by Murfix
We brake by shorting motor phases at the correct timing. This allows current to flow. The generated power is dissipated through heating of the wires and mosfets. With regen, we don't have to dissipate the power because we now have a use for it --> battery.

You can try this by connecting 2 motor wires together and then try to spin the motor. It will be a lot harder!

Re: Implementing regenerative braking on electric longboard

Posted: Jun 04 2014 11:29am
by Hummina Shadeeba
Murfix wrote:We brake by shorting motor phases at the correct timing. This allows current to flow. The generated power is dissipated through heating of the wires and mosfets. With regen, we don't have to dissipate the power because we now have a use for it --> battery.

You can try this by connecting 2 motor wires together and then try to spin the motor. It will be a lot harder!
But if it's only a couple percent efficient are we mostly using power or retrieving power when we brake? Is it up to the batteries' c rating at all? Or are u saying it's not really much power used as the controller is just connecting the two wires?

Re: Implementing regenerative braking on electric longboard

Posted: Jun 14 2014 12:02pm
by Hummina Shadeeba
on youtube there's a video of the boosted board guy stating their board gets about 40percent regen. that's pretty substantial. I wonder how true it is and I wonder why people dont integrate it into the controller more often if it's possible.

Re: Implementing regenerative braking on electric longboard

Posted: Jun 14 2014 5:30pm
by psychotiller
Hummina Shadeeba wrote:on youtube there's a video of the boosted board guy stating their board gets about 40percent regen. that's pretty substantial. I wonder how true it is and I wonder why people dont integrate it into the controller more often if it's possible.
Really, I just wonder why their customers arent saying anything about it.

Re: Implementing regenerative braking on electric longboard

Posted: Jun 14 2014 5:33pm
by torqueboards
Hummina Shadeeba wrote:on youtube there's a video of the boosted board guy stating their board gets about 40percent regen. that's pretty substantial. I wonder how true it is and I wonder why people dont integrate it into the controller more often if it's possible.
If that was true -- wouldn't they get more then 6 mile range?

Re: Implementing regenerative braking on electric longboard

Posted: Jun 14 2014 5:51pm
by psychotiller
torqueboards wrote:
Hummina Shadeeba wrote:on youtube there's a video of the boosted board guy stating their board gets about 40percent regen. that's pretty substantial. I wonder how true it is and I wonder why people dont integrate it into the controller more often if it's possible.
If that was true -- wouldn't they get more then 6 mile range?
Yeah, 40%..shouldn't they be getting closer to say 8 miles?

Re: Implementing regenerative braking on electric longboard

Posted: Jun 15 2014 1:11pm
by Daggers
Murfix wrote:As furp said, it's actually regen coasting instead of regen braking. When the motor is forced to spin (ie. coasting) it acts as a generator. We coast a lot so we can regen a lot.

The esc has to be able to send the current in the opposite direction and you can only store the amount of current into your battery that is defined by the C-rate for charging of your pack. There's also some losses to be taken into account, mainly in the ESC, because all the power that it uses (switching and stuff) has to come from the generator instead of the battery.

Short: you need a special ESC and the higher the charging C-rate, the more efficient (up to a certain point).
Regenerative braking is starting to seem like a good idea now. What ESC would I need for this? And do I just use that ESC and that's it or is there anything else to do for it to work?
I'm imagining if the battery dies and I'm stranded, I can push while slightly braking to recharge the batteries. I do realize this will definitely make it harder to push but if I'm going down a hill, I can control my speed with the regen braking and charge the batteries at the same time.

Found this guy: http://www.rc-monster.com/forum/showthread.php?t=18978 talking about how his EZrun does regen braking. Does that mean it's automatically built in and using an EZrun esc will charge the batteries while braking?

Re: Implementing regenerative braking on electric longboard

Posted: Jun 16 2014 2:17am
by Murfix
I hope you have also read my rectification of that post, because it was actually wrong.

However, I think regen braking might be a useful addon, I haven't tested it yet and I can't tell you how to integrate it. I suggest looking up some documentation about ESC's that claim to have the regen braking option.

Re: Implementing regenerative braking on electric longboard

Posted: Jun 16 2014 2:02pm
by beto_pty
I have an ezrun 150 controller and get no difference in milage due to regen braking as opposed to when i use my hobbyking 150... and I run one of two courses every day.. mostly in the same manner, at about the same weight, having charged/balanced the cells every time... final voltages on my bateries are within 0.2-0.3 volts or each other day depending on a million variables..
If there were to be a difference (which i believe there isnt) it is so small as to be negligible or even unmeasureable, which in my book puts it in the "no difference" category

unfortunately just wishing that a new technology works isnt enough...it actaully has to be noticeable and provide a positive effect, as it will necesarily bring about added complexity, higher weight, or higher cost.. :shock: probably all 3.

Regen coasting, if it were to exist would be less efficient than regular (nonregen)coasting as not 100% of the energy drained from the motor acting as a generator during coasting is recharged into the batteries, so the decrease in coasting distance is necesarily significantly less than the "distance charged" into the battery...

If you want to sell a board and advertise regen breaking as a marketing strategy that is one thing, as it probably technically speaking does it... if you plan to go an extra half mile due to the regen capabilities that is another matter, as in reallity it does not... (again the disclaimer...unless you bomb the Mont Blanc every day in which case other dynamics might apply)

Re: Implementing regenerative braking on electric longboard

Posted: Jun 16 2014 2:10pm
by torqueboards
I agree -- while it still does most likely have it.. It's not worth much in gold besides the marketing aspects.

I like this one here..

http://www.rc-monster.com/forum/showpos ... stcount=16
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.

Re: Implementing regenerative braking on electric longboard

Posted: Jun 17 2014 10:11pm
by Hummina Shadeeba
torqueboards wrote:I agree -- while it still does most likely have it.. It's not worth much in gold besides the marketing aspects.

I like this one here..

http://www.rc-monster.com/forum/showpos ... stcount=16
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.
I don't know what he's saying if anything. It seems he's saying the forces are too large when braking. The tesla is getting 80% regen and it being a car there's a lot more force when that's moving. What's in tesla's controller I wonder....and now be looking up.