Interesting insight into why Brammo doesn't do regen...

I'm considering an electric build, and top of the list of requirements for me is regen braking. Not for the extra juice, but specifically for the braking effect. From your post on day 2 of the races it seems like if nothing else it would be a great marketing feature if you're trying to convert ICE riders to electric.

http://brammofan.wordpress.com/2009/07/22/brammo-enertia-regen/

1. Not enough energy to be regenerated off the rear wheel of a lightweight motorcycle....
2. Regen turns your motor into a generator – which means it’s working when it might otherwise be resting. ...
3. Control – regen is a variable parameter and probably requires an additional hand control to be done properly....
4. Range – in most cases, you’ll experience greater range by “free wheeling” and coasting with no regen than you would if regen kicked in when you let off the throttle....

BTW - I'm at the eGrandPrix right now, and all the bikerdudes are asking about engine braking and are concerned about how electrics normally coast rather than engine brake. The closest to engine braking is regen, of course.

I mostly agree that regen is overrated. However, there are a number of problems with the quoted reasons...

1. The weight of the bike is a red-herring (false lead). I used to think the same thing. But, erm, the laws of physics disagrees. Yes, less energy will be recovered by a 300lb bike decelerating than a 10 ton truck. However, proportionally less energy is required to get the bike moving again. Hence, regen can be as effective on a motorcycle as a bus. However, there's lots of other things that come into the effectiveness equation - but the weight of the vehicle isn't one of them.

2. This is the most valid point. Having the motor provide "X" kW of braking force (as a generator) is as hard on the motor as having it provide "X" kW of acceleration. However, if the amount of regen is capped then this problem can be avoided.

3. Yes, regen is a variable parameter. Guess what? So is braking. Control it with the same inputs (the brake levers) and the problem is pretty much solved.

4. Agreed - if regen were controlled simply on letting off the throttle would make for a bad riding experience as well as a poor use of regen. However, I'll go one step further - you'll get better range by coasting to stops rather than using regen. This is true even with a 10 ton bus (of course it's difficult to coast to a stop in a bus!) The reason is to do with the losses introduced into the system. Regen is never 100% efficient (heat is produced), minimize braking (physical or electrical) and you minimize your energy losses. "Minimizing your energy losses" is engineer speak to "get better range".

Were the original bullet points from a Brammo engineer? If so they need to raise their game. If another company spokesperson they should talk to the engineers. That's what I did and they set me straight... :)

4. Agreed - if regen were controlled simply on letting off the throttle would make for a bad riding experience as well as a poor use of regen. However, I'll go one step further - you'll get better range by coasting to stops rather than using regen. This is true even with a 10 ton bus (of course it's difficult to coast to a stop in a bus!) The reason is to do with the losses introduced into the system. Regen is never 100% efficient (heat is produced), minimize braking (physical or electrical) and you minimize your energy losses. "Minimizing your energy losses" is engineer speak to "get better range".

John, I think you've overlooked one very important piece of the puzzle, as it applies here. 10 ton buses/trucks can't freewheel, because of their weight, so they would be forced to use regen in their attempt to become a bit more efficient. A 100, 200, or 300 pound eBike doesn't have that problem, and since freewheeling is more efficient than regen, it's the one you choose, if you're only going to have one. You choose it because its not only simpler, it's also considerably cheaper, while having the added benefit of being more efficient.

Were the original bullet points from a Brammo engineer? If so they need to raise their game. If another company spokesperson they should talk to the engineers.

I recently had an email exchange with Brian Wismann, Brammo Director of Product Development,

Edit: Note, I'm neither saying you're wrong, nor arguing with you. Strangely enough, the second time I read what I wrote, it seemed argumentative. It wasn't meant to be.

This strikes me as one of those things that may not work now, but eventually get perfected and works quite well.

I am not sure how they will do it.

Perhaps some computer controls and algorithms to sense when you begin to do enough stop and go driving to provide a benefit and the regen kicks to the breaking like 4 wheel drive does for automatic 4 wheel drive on a car.

Perhaps it can be switched on off or there is an additional manual control and we riders learn to use it at the right times.

myocardia:

OK - I guess I over-reached with my argument (no surprise there, eh?). A sedan can certainly "free-wheel" or coast and you could apply the same arguments by substituting "small sedan" in all of the above. I'm not sure I entirely agree that a 10 ton truck can't freewheel. Even if it can't the relative energy it can recover via regen is the same as the relative energy the lighter two wheel vehicle can (assuming the same technology used on both).

I didn't take your post as argumentative - and I very much agree that if you're only going to choose one then choose the simpler one. I started out briefly saying "I'm no fan of regen" but I still contend that the four items as listed are lousy reasons not to implement regen. Note that none of those four speaks to your assertion (which could be classed as the venerable KISS principle).

Some folks like regen for a different reason - it creates an effect somewhat similar to engine braking from an ICE vehicle. A lot of my engineer friends say stuff like "I know it's not great but I just gotta have it - it's cool". A lot of consumers just see it as a "should have" if not a "must have" - Brammo is swimming upstream on this one. Nothing wrong with that - but I dare say when they have the time they'll implement it and make it sound like they were going to do it all along. But maybe I'm being too cynical (it's been that sort of a day for me...)

love it or loath it regen is here and will likely be implemented in more, not less, motorcycles (BTW, the Brammo is an electric motorcycle not an ebike).

Finally I apologize for the line about the Brammo engineers - that was a dumb thing to say.

John, funny you should say 'A lot of consumers just see it as a "should have" if not a "must have"'. I came very close to saying something very much like that in my last post, and I couldn't agree with you more. Whether or not it has any use at all makes no difference. If the consumer thinks it's needed, it's his money, so it must be needed.

And actually, a 20,000 lb truck can freewheel, but only if the driver depresses the clutch pedal. If the driver doesn't want to break the law, though, (it's not legal to operate a vehicle in neutral, or with the clutch depressed, unless you're in the process of changing gears), then what happens when he takes his foot off the accelerator? Right, engine braking, which as you know, is exactly the same thing that happens to an EV that doesn't have the capability to freewheel. Sure, all three are now coasting, but only the one with a freewheel installed is efficiently coasting, assuming no laws are being broken.

Some may see that as splitting hairs, but take it from me, there's a huge jump in efficiency between the different types of coasting. Like more than a 10 MPG jump in efficiency, in ICE terms. Definitely not something anyone I know would call inconsequential. BTW, I never argued with your first point. I agreed with it completely.

As a consumer I would definitely part with money for regen braking on a motorcycle. As to how much money, well that remains to be seen.

myocardia:

OK - I guess I over-reached with my argument (no surprise there, eh?). A sedan can certainly "free-wheel" or coast and you could apply the same arguments by substituting "small sedan" in all of the above. I'm not sure I entirely agree that a 10 ton truck can't freewheel. Even if it can't the relative energy it can recover via regen is the same as the relative energy the lighter two wheel vehicle can (assuming the same technology used on both).

This might be correct on some level, but is generally misleading and wrong.

The important "relationship" is the one between different power losses.
You are talking about the relationship between energy needed to accelerate compared to energy recovered by deceleration.

The power loss due to friction with the air, compared to the power loss due to braking, is much higher for a small vehicle with poor aerodynamic shape, like a motorbike or a scooter.

Believe it or not, a bus or a truck are much more aerodynamic than a scooter, relative to their mass and volume!

Large vehicles with smooth surfaces loose relatively little energy to wind resistance, compared to their rolling resistance and the kinetic energy stored as E=1/2mV^2 .

That is why a truck (particularly a full one) will coast much further than a motorbike (when freewheeling on flat ground).

Relatively speaking, an elephant has a much smaller surface area than a mouse! But that might be off topic...

Mik's answer agrees with my understanding as well.

If you look at the relative energy budget of a car vs a scooter, the scooter spends a larger fraction of it's energy usage overcoming air friction, and therefore a smaller fraction of it's energy altering it's momentum. So in a car, you might spend 1/2 of your energy on air friction and 1/2 on acceleration, but in a scooter you might spend 2/3 of your energy on air friction and 1/3 on acceleration (imaginary numbers used to demonstrate the concept).

So a car might be able to recover 1/2 of it's acceleration energy, which translates into 1/4 of it's entire energy budget. If a scooter can recover 1/2 of it's acceleration energy, it's only getting 1/6th of it's total energy budget back. So a scooter with regen doesn't increase it's range nearly as much as a car does.

Of course, if you built the scooter with a very aerodynamic shell, the whole balance would change, and regen might provide a huge increase in range (but so would the aerodynamic shell).

However, that doesn't change the fact that regen is an important part of a good vehicle design. First, conventional braking is wasted energy, which we always should avoid if we can. EV customers know this at some level, so they will prefer a vehicle with regen over one without, even if they don't work the math to figure out the exact range increase. And it does save wear on the brake pads.

If you read the whole article, the conclusion was that Brammo felt the added complexity of regenerative braking was not worth the perceived benefits. That seems like a reasonable conclusion.

After riding the Vectrix, I love regenerative braking. There is a different feel to it than with standard brakes. And as the hypermilers will tell you, any braking is a waste of energy, at least with regenerative braking you are giving a little back.

1. ICE vehicles, large and small, can be designed with an "overdrive" that lets them free-wheel (coast) when in the overdrive "gear".

My 1994 Dodge Grand Caravan has this very nice, energy-saving feature. When in the highest (Drive) automatic transmission setting, it coasts unless I turn off the "overdrive" with a switch on the dash.

2. To do regen well, one needs to have coasting AND regen available, not just regen in place of coasting.

3. The amount of regen can be "requested" by the (perhaps rear ?) brake lever position, using a first half-inch (or so) of travel where the mechanical brake is not yet engaged.

4. It might be preferred to have the other brake (front ?) strictly mechanical, and have it NOT cut off the motor drive, so that the rider has much SAFER control in starting up on steep grades.

John, does your scooter design have this motor-on braking?

John, does your scooter design have this motor-on braking?

No, when the brakes are applied the controller is disabled. As far as I know (and I agree it's a small sample set) you're the only one I've heard from that wants to be able to apply motor and brake at the same time. Other EV riders have responded that they are fine with the situation as is. Ultimately we could make it a user controlled option in some way - but not with this release.

Looks like I dug myself a hole here. Really my only point is that the weight of the vehicle alone is not a strong element in the discussion of regen. I then went on to completely screw up with my explanation. Sorry about that (rest assured I'm not the chief engineer at CuMoCo so don't be too alarmed by my limited understanding).

However, I still think I stand by my opinion that the four bullet points presented at the beginning of this thread (and what I responded to) were not a very satisfactory reason not to include regen. There are other reasons for and against regen on a motorcycle - but, IMO, those four presented are pretty weak.

This might be correct on some level, but is generally misleading and wrong.

The important "relationship" is the one between different power losses.
You are talking about the relationship between energy needed to accelerate compared to energy recovered by deceleration.

The power loss due to friction with the air, compared to the power loss due to braking, is much higher for a small vehicle with poor aerodynamic shape, like a motorbike or a scooter.

Believe it or not, a bus or a truck are much more aerodynamic than a scooter, relative to their mass and volume!

Large vehicles with smooth surfaces loose relatively little energy to wind resistance, compared to their rolling resistance and the kinetic energy stored as E=1/2mV^2 .

That is why a truck (particularly a full one) will coast much further than a motorbike (when freewheeling on flat ground).

Relatively speaking, an elephant has a much smaller surface area than a mouse! But that might be off topic...

Hey, Mik, what's happening, man? Actually, I don't disagree with what you said, however, it has zero to do with what I said. My post had absolutely nothing to do with aerodynamics. It had to do with engine braking, which is why I mentioned engine braking, and not aerodynamics.:) See, unless your EV has a freewheel, or a transmission with a user-deployable clutch, it will not freewheel when you stop accelerating, it will in fact engine brake, just like your ICE automobile with a 5 speed manual transmission will.

Robert

Looks like I dug myself a hole here. Really my only point is that the weight of the vehicle alone is not a strong element in the discussion of regen. I then went on to completely screw up with my explanation. Sorry about that (rest assured I'm not the chief engineer at CuMoCo so don't be too alarmed by my limited understanding).

Not at all. You obviously have a much better understanding of vehicle physics than the executives at Brammo.

However, I still think I stand by my opinion that the four bullet points presented at the beginning of this thread (and what I responded to) were not a very satisfactory reason not to include regen. There are other reasons for and against regen on a motorcycle - but, IMO, those four presented are pretty weak.

Agreed. Obviously regen wasn't included on the Brammo EV's for monetary reasons, not safety or efficiency reasons. Because, let's face it, who doesn't want to add only 6 or 8% more mileage to their EV?

Robert

Agreed, I've got up to 14.5% regen return in city driving! My average is 7%. I still coast when i can as that is the most efficient, however this can be annoying to other drivers behind you.(even though you're doing them a favor as far as saving fuel) The aerodynamics vs wieght is a good point,an almost fully enclosed and aerodynamically superior scooter would be a big breakthrough. It's true that the "cool" factor is a big thing with allot of people also. I rigged both my scooters with regen and would not buy one now without it...unless I could buy one cheaper without it and convert it for less.

Trading brake dust for Watt hours is a no brainer, right?

Absolutely right. Any increase in range is good. And any battery boost you can get just before you hammer the poor puppies with max current drain during acceleration from a dead stop is good. Original bullet point #2 is the only valid one. Coasting can be implemented by control software.
Even the now ancient eGo cycles have regen. And they did it with a series wound DC motor. I still don't know how they pulled that off. But it works VERY well. And a new Kelly controller with regen is only about 50 bucks more expensive than one without regen. On a $10K ride, I think they could have made room for a $50. Brammo was sloppy and lazy on this point. Give me a bike designed by engineers, not artists.