The ideal regen system

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jdh2550_1
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The ideal regen system

OK, now I know what the ideal controller is ;-) Let's hear what makes the ideal regen system.

It strikes me that the goals of the ideal system are (not necessarily in this order)

1- Recover the most energy possible
2- Integrate seamlessly into the riding experience

Starting with number 1 I think that means that you need super capacitors in the equation because the generator will be able to generate far more than the max charge capacity of the average battery. You'd either need the controller to "throw away" this extra current or somewhere else to store it. Hence the need for super caps. And, as pointed out elsewhere you'll need a way of stepping up the voltage output of the super caps to the system voltage. Sounds tricky and thus expensive. Is it better to just have the controller limit the max charge seen by the batteries?

With all the talk about battery balancing, if the charge is going back to the battery pack then I presume it would be most effective to use it as a "string charge" rather than a "bank charge". So, would this mean that battery balancers become more of a necessity?

For number 2, how best should the regen feature be controlled? Should it be entirely separate from the mechanical brakes? Or should it always be applied in tandem with the application of the brakes? If the latter, then should it be both brakes or just the rear brake? On a m/c you normally do the majority of the braking with the front brake (look at any production m/c and you'll see that it has far more braking power on the front wheel rather than the rear). Good m/c practice dictates that you always use both brakes - but I know a lot of people (me included) that often just use the front brake and only use the rear brake in emergency stop situations. I believe that some bikes have "brake balancing systems" whereby they always apply both brakes even when you only apply the front brake (normally bigger sports-tourer bikes).

The Vectrix goes for the complete separation of controls - but as Mik notes the two choices can interfere with each other. Especially because applying the front brake seems to not be very compatible with also using regen.

If I were to separate the controls I'd likely have left hand for the front brake, right hand for the rear brake and right foot for the regen feature (on an m/c with a gearbox right foot is rear brake).

If I were to have regen work in tandem with the brakes then ideally I think I'd have it set up whereby if just the front brake is applied then regen works at 50% capacity on the rear wheel (obviously). When I say 50% I mean that it would vary between 0 and 50% dependent on the amount of front brake applied. If the back brake was applied then I'd have it work at 100% capacity (varying between 0 and 100% based on amount of rear brake applied).

Do folks out there no how other bikes with regen are set up?

jdh2550_1
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Re: The ideal regen system

It won't edit my first post:
(a) I got my left and right hand mixed up. Left hand is rear brake, right hand is front brake. Right foot is right (and is still the rear regen switch).
(b) In the paragraph about super caps and regens it should say that the generator will generate more than the peak charge rate (not capacity).

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

rgx
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Re: The ideal regen system

Do folks out there no how other bikes with regen are set up?

I don't know about bikes, but I have a Honda Civic hybrid. It works like this, as soon as you let off the gas pedal it shuts down the engine and starts regen. The regen power is related to the speed of the vehicle, which basically means the regen torque is about constant. This very much feels the same as engine breaking with a normal car. You can reduce regen gradually by applying a light pressure to the gas pedal - until it actually goes to EV mode at low speeds (ICE still not operating).

By applying the brake pedal regen increases. When breaking harder, beyond full regen, the disc brakes will be applied. During a complete braking to a stop, regen and mechanical brakes are regulated to achieve a constant resulting brake force (remember, the regen max torque will increase as speed drops, because max regen power is constant). At the end of the braking, just before the stop, the mechanical brakes are applied harder and regen gradually eases of as engine speed reduces to zero.

So I think ideally regen shall be controlled by the rear brake lever. It should be gradual, and moderated by the lever, not only on/off. And to be truly (hypothetically) ideal, it should compensate mechanical brake pressure for variations in regen torque, to keep brake force constant as long as brake lever force is constant. For a bike, I don't see the benefit of regen as soon as you lift of the gas, a bike stops quickly anyway when free wheeling.

(This post doesn't prevent me from arguing that regen is of limited benefit for a light vehicle with high air drag such as a motor bike. Only heavier vehicles such as cars or perhaps a sidecar can really benefit. So don't overdo it.)

LinkOfHyrule
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Re: The ideal regen system

I like your idea. In most situations, you can use the rear brake to slow yourself. So, the rear brake should be the regen; no mechanical brake needed. The front brake should be a good strong disc for those emergency stops.

My next bike will have something akin to regen. We really didn't know what to call it, so we dubbed it "plug braking". Basically, instead of putting energy back into the batteries, you just dump it through a big honkin' variable resistor or (in my case) a MOSFET that can dissipate a lot of heat.

Now, I know what you're thinking: WTF? You're just gonna dump all that good energy away?

There's really only one reason to pick this over regen: cost. If you have a cheap controller that works fine and don't want to just get rid of it in favor of a more expensive controller just because it has regen, then you can just add a few FETs or a big potentiometer and not have to spend $100+ on a nice controller. If you use supercaps, your ALSO going to have to add the cost of that, plus it's necessary power system.

Why not just have caliper brakes? Well, no reason really. However this still has regen braking's advantage of not wearing down brake pads. Very good thing to have if you need to control your speed down steep hills a lot. Besides, with the actual range increase regen offers, it's not that much of a difference in range.

Anyway, Fechter thought up a very clever regen brake: a controller. Basically, if you hook a cheap controller up BACKWARDS with a few big diodes, you can use it as a regen braking system.

My biggest problem is how to actually ACTIVATE the brake. I want the rear brake lever to be the regen/plug, not another throttle. I'm going to have to make some sort of pot box.

The author of this post isn't responsible for any injury, disability or dismemberment, death, financial loss, illness, addiction, hereditary disease, or any other undesirable consequence or general misfortune resulting from use of the "information" contai

jdh2550_1
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Re: The ideal regen system

(This post doesn't prevent me from arguing that regen is of limited benefit for a light vehicle with high air drag such as a motor bike. Only heavier vehicles such as cars or perhaps a sidecar can really benefit. So don't overdo it.)

Actually, I agree with this. But, seeing as the next project I'm thinking of is with the prime reason of selling it I decided to be like a sheep and follow the regen crowd...

Baaa!

:-)

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

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Re: The ideal regen system

Left hand is rear brake, right hand is front brake. Right foot is right (and is still the rear regen switch).

I agree, thats just how I would configure the controls for a capable bike rider.

However, it might be that once EV bikes catch on big time that the majority of riders would be the kind that never practices emergency braking, because it might be dangerous.....

In that case an integrated electronic system that engages regen braking first, then adds in disk brakes including ABS would be preferable, even if it does not achieve 100% of the breaking power of a properly trained rider.

Not an easy feat to design this; and get it past the RTA etc.

One would of course still have to be able to use full disk breaking power when all electrical systems are down.

Mr. Mik

This information may be used entirely at your own risk.

There is always a way if there is no other way!

garygid
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Re: The ideal regen system

Where does usatracy get this "magic" 5% recovery by having regen?
Where is this post that is being quoted?

In careful driving on the flat, there would be almost no regen recovery.

In driving on hills, the possibility is for more than this 5%, I would think.

And, on hilly trips, if one got 20% recovery on half the trip (perhaps a 10%
average ?), adding 5 miles to a 50 mile range is not totally insignificant.

When properly implemented (it should only come on when the brake is applied
so that coasting is still possible), the application should be gradual with
the first travel of the brake lever, before mechanical braking takes effect.

There should be no "sudden" reversal or violence with a proper implementation.

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

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Re: The ideal regen system

In Mik's observation driving with Vectrix, he discovered, that with Regen braking, his range increased 10%-12%.
He also discovered, that by regen-ing gently, he regenerates more energy into battery than a sudden strong regen.

Additionally, I've read in a local science papers about EVs, that aprox. 50% of regen energy goes back into the battery. The rest goes to heat.

antiscab
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Re: The ideal regen system

Additionally, I've read in a local science papers about EVs, that aprox. 50% of regen energy goes back into the battery. The rest goes to heat.

that 50% piece of data, out of context is almost irrelevant.
the amount of kinetic energy recovered and actually stored in the battery depends on motor effiency at tested speed, motor speed, controller efficiency, battery temperature, battery chemistry and type, battery soc, actual regen rate, etc.

what were the assumptions/setup when the author calculated/measured that efficiency?

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

Mik
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Re: The ideal regen system

In Mik's observation driving with Vectrix, he discovered, that with Regen braking, his range increased 10%-12%.
He also discovered, that by regen-ing gently, he regenerates more energy into battery than a sudden strong regen.

Additionally, I've read in a local science papers about EVs, that aprox. 50% of regen energy goes back into the battery. The rest goes to heat.

Well,I just re-read the main thread about this at: http://visforvoltage.org/forum/3369-vectrix-real-world-regen-braking-testing and there were a number of problems in my measurements:

As already mentioned in the thread later on, during the EC part of charging there is some actual current flow into the battery. The voltage increases by 1-2V compared to the end of CC part. How much difference that makes, I do not know.

What I did not know back then was the high self discharge rate of NiMH, particularly in the first 24hrs. So I basically do not know what those results mean, because the self discharge rate might have been equal to, or different to the charge amount missed during the abandoned EC charge part.

And I never did the planned commuting without regen, because 2 weeks after the first regen tests the motor controller fried and Vectrix canceled my warranty. It took me 3 weeks to repair the motor controller myself, but 9 days later it was frying again. After another 3 days I managed to fix it properly; that was followed by another blown fuse a 12 days later, which I sourced and replaced within 2 days.

And then I finally had some time to read up more about batteries. And as a result I canceled the plans to deliberately run out of charge for testing purposes.

In short: I don't know how much the regen really adds to the range, but it is so little that it is not easily measured with accuracy.

This information may be used entirely at your own risk.

There is always a way if there is no other way!

AndyH
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Regen Not Worth It? Depends...

Here are some real-world numbers:

7000Km trip
100.7 kWh used
98.3kW supplied thru charging
2.4 kWh supplied thru regen

Regen in mountainous areas provided 12.6 to 17.7% regen

This wasn't a car or a scooter - it was an electric bicycle.
http://www.endless-sphere.com/forums/viewtopic.php?f=29&t=7134&start=525#p107725

fisher727
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Re: Regen Not Worth It? Depends...

I am including a report I made on my experience driving my Electric car with regen brakes. I hope it gives you some in site on what it is like to operate a vehicle with regen brakes.

I now have 8,500 mile since I installed the SP100 Greensaver batteries
in my 1996 Force a year an a half ago. The car has been driven 90% of
the time on my commute to work and back. I have not noticed any
change in the capacity of the batteries in that time. The trip from
work starts with the batteries charged and amp meter reading 00.00. I
drive the first 6 miles in town with stop lights every half mile.
This is hard because the batteries are full and the regen braking is
hard to get much out of. The next 10 miles is highway driving which
starts with two street lights about 1 mile apart and with speeds of 55
miles per hour. The next 17 miles is curvy mountain roads with speeds
averaging 35 miles per hour and no stops. The next 7 miles is a steep
curvy climb of about 2,000 feet. The last 1.8 miles is on a steep dirt
road and climbs 400 feet. The total trip uses 80 amp hours, with an
altitude gain of 4,200 feet and 41.8 miles driven. I check the
batteries when I get home and they are 12 volts on average more on
warmer days and less on colder days this is a very depressed voltage
and would read higher if I waited a couple of hours. I plug the car in
and charge it until I reach 50 amp hour on the meter for the drive the
next day.
The next day I start with 50 amp hours on the meter and drive the
first 1.8 mile and note the amp hour meter is still at 50 amp hours.
The next 7 miles is done with the generator on full a 35 mph and the
amp meter reading 60 amp input into the batteries. After the seven
miles down hill the amp meter reads 44 amp hours. I will continue the
drive and at 24 miles the amp meter will read 50 amp hours the same as
when I left my house. I arrive at work with the amp meter reading 70
amp hours for a total of 20 amp hours used to get me to work.
I only do this driving in the Fresno,California area during the
summer months for fire season a span of 5 months. The rest of the year
the car does very little.

Eric Fisher
www.SiliconeBatteriesUSA.com

AndyH
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Re: Regen Not Worth It? Depends...

Hmmm... Could city driving be best for regen? From the Society of Automotive Engineers...
http://www.sae.org/technical/papers/1999-01-2910

Abstract:
The possibility of recovering vehicle kinetic energy is one inherent advantage of electric and hybrid electric vehicles. When a vehicle drives in heavy traffic, for example, in New York City, more than half of the total energy is dissipated in the brakes. Therefore, recovering braking energy is an effective approach for improving the driving range of EV and the energy efficiency of HEV.

In this paper, three different braking patterns are investigated for evaluating the availability of braking energy recovery. The results indicate that even without active braking control, a significant amount of braking energy can be recovered, and the brake system does not need much changing from the brake systems of conventional passenger cars.

Mik
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Re: The ideal regen system

In Mik ...... also discovered, that by regen-ing gently, he regenerates more energy into battery than a sudden strong regen.

How did I supposedly do this??? I'm not aware of it!

I'm not sure if it is quite correct, either!

On a theoretical basis, if you coast at speed and brake hard at the very end, more energy will be lost due to wind resistance.
If you brake hard early on, until you are so slow that you only just coast to a standstill, the energy loss to friction with the air will be minimized.

But that is just theoretical and might, or might not, be outweighed by varying grades of efficiency of the regen system at different "loads". It might produce much more heat at high energy regen, but I have no way of measuring this.

This information may be used entirely at your own risk.

There is always a way if there is no other way!

AndY1
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Re: The ideal regen system
In Mik ...... also discovered, that by regen-ing gently, he regenerates more energy into battery than a sudden strong regen.

How did I supposedly do this??? I'm not aware of it!

I'm not sure if it is quite correct, either!

On a theoretical basis, if you coast at speed and brake hard at the very end, more energy will be lost due to wind resistance.
If you brake hard early on, until you are so slow that you only just coast to a standstill, the energy loss to friction with the air will be minimized.

But that is just theoretical and might, or might not, be outweighed by varying grades of efficiency of the regen system at different "loads". It might produce much more heat at high energy regen, but I have no way of measuring this.

I think I read that somewhere in the heap of all your reports ;-)

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