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Carry weight for regenerative brake improvement


Demargon

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Can't use darknessbot in my android. If anyone have it installed can do some testing and determine how high is the regenerative value with and without carrying extra weight.

By the way ¿there is a optimal speed for regenerative braking?

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11 hours ago, Demargon said:

hen I carry a full backpack the regeneration of battery charge is highest

Maybe, but I suspect that the extra weight would cost you more energy when you are going on the straight and level and uphill than you would ever gain from going down hill -- unless you live in a place where everything is downhill, whether you are going to or from your destination.

This would be the opposite place from where I lived when I was a child going to school -- Every day I had to walk ten miles uphill every day -- both coming and going. (Always in the snow, by the way.)

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The point is pick a rock or water in the top of the hill and leave it when his potential energy are depleted (at the end of the slope). I don't have any idea for measure the benefits and if worth the effort, carry heavy thinks is stressful

¿how can measure the regenerative braking performance?

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More weight means more potential energy that goes into regenerative charging of the batteries (and extra friction, mostly of the tire). Potential energy is linear in mass, so approximately (assuming regen efficiency and everything else is constant for a certain route if you only change your weight), increase your (wheel + rider) weight by x% and you get x% more back.

This means, pack 10kg of or rocks into your backpack (10% of 100kg which for simplicity assumes 80 kg rider + 20 kg wheel) at the top of a hill and you get 10% more battery charge back going down than without the rocks.

You could do the experiment, make sure everything else stays the same (battery % at the top, temperature, battery health, your speed, ...) and find a big enough hill so your estimated difference in regeneration can be seen on the battery status. Ideally, you should have a few percentage points of difference from regen so either loooong hill or lots of rocks.

An example: 3 km at 7% average incline gives me 10% back on my ACM 1300 (very roughly, and I may remembering wrong). If I were to put 30 kg of rocks into my backpack at the top, it should be 13% back instead. This could be seen on the battery status clearly.

Not sure if carrying tons of rocks is worth it for the bit of battery. But it's a nice idea to try, sounds crazy at first, but the longer you think about it, the more interesting the idea is.

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On 5/6/2017 at 1:22 AM, dbfrese said:

This would be the opposite place from where I lived when I was a child going to school -- Every day I had to walk ten miles uphill every day -- both coming and going. (Always in the snow, by the way.)

The way I've heard it, in the "olden days", kids had to ski to and from school in a blizzard for 40 kilometers, uphill both ways, with a broken leg and a hungry wolf pack on their tail ;)

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On 5/6/2017 at 3:27 AM, meepmeepmayer said:

This means, pack 10kg of or rocks into your backpack (10% of 100kg which for simplicity assumes 80 kg rider + 20 kg wheel) at the top of a hill and you get 10% more battery charge back going down than without the rocks.

I doubt the regenerative braking efficiency is nowhere near 100%, ie. (a large) part of the energy gets lost as heat... Doubt it's actually worth it in the end, but still it would make an interesting experiment. Also, some boards seem have fried the mosfets during strong braking with heavier riders... :P Guess that's where most of the heat burns off  ( see for example https://electronics.stackexchange.com/questions/56186/how-can-i-implement-regenerative-braking-of-a-dc-motor  , when the low-side mosfets short the motor coils, most of the energy probably burns off in the mosfets and in the wiring )

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The efficiency is irrelevant, as long as it does not depend on weight, it's already factored in there. The argument simply is, since you add linearly more energy with weight, and that energy goes into recharging (this assumes everthing else, especially the friction of the tire, stays the same which probably won't work out so well with 30kg extra), you should have a proportional increase in energy gained. So x% more overall weight gives you x% more recharging (at whatever efficiency that it has in both cases, as long as it is the same efficiency).

This is just a rough estimate to get an idea which situations could be used so you even see a difference from recharging with different weights.

15 hours ago, esaj said:

Doubt it's actually worth it in the end, but still it would make an interesting experiment.

Agreed. But maybe if I feel like lobbing 30kg of rocks around some day, and don't brake too hard:P

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I disagree with the notion of regenerative braking because unlike the simple electric motor bolted in place (allowing torque)to a fixed surface the EUC is a space age electronic balance between the riders weight applied to the pedals below the center of the wheel and a self balancing current applied to parts of the 'wheel motor' as determined by a logic circuit.

Going uphill or downhill or level or remaining stationary requires self balancing current to the wheel via a circuit. 

While some riders report battery level increases while going downhill, the thought of simply reversing current through the main board to the battery seems unlikely if not hazardous.

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As work in gravity =mass *gravity *height, and work=energy, obviously if the we carry more weight (mass*gravity }, more work will be done by it. So more energy have to be absorbed anyhow, dissipated as a heat or transformed to a battery charge. Of course minus the losses, friction and energy required to keep the system alive, which (my opinion) is minimal. 

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On 5/5/2017 at 6:27 PM, meepmeepmayer said:

More weight means more potential energy that goes into regenerative charging of the batteries (and extra friction, mostly of the tire). Potential energy is linear in mass, so approximately (assuming regen efficiency and everything else is constant for a certain route if you only change your weight), increase your (wheel + rider) weight by x% and you get x% more back.

This means, pack 10kg of or rocks into your backpack (10% of 100kg which for simplicity assumes 80 kg rider + 20 kg wheel) at the top of a hill and you get 10% more battery charge back going down than without the rocks.

You could do the experiment, make sure everything else stays the same (battery % at the top, temperature, battery health, your speed, ...) and find a big enough hill so your estimated difference in regeneration can be seen on the battery status. Ideally, you should have a few percentage points of difference from regen so either loooong hill or lots of rocks.

An example: 3 km at 7% average incline gives me 10% back on my ACM 1300 (very roughly, and I may remembering wrong). If I were to put 30 kg of rocks into my backpack at the top, it should be 13% back instead. This could be seen on the battery status clearly.

Not sure if carrying tons of rocks is worth it for the bit of battery. But it's a nice idea to try, sounds crazy at first, but the longer you think about it, the more interesting the idea is.

Until you overstress, or overheat or over tilt the wheel and it shuts off.. and you end up underneath that ton of rocks. 

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16 hours ago, Bob Eisenman said:

I disagree with the notion of regenerative braking because unlike the simple electric motor bolted in place (allowing torque)to a fixed surface the EUC is a space age electronic balance between the riders weight applied to the pedals below the center of the wheel and a self balancing current applied to parts of the 'wheel motor' as determined by a logic circuit.

Going uphill or downhill or level or remaining stationary requires self balancing current to the wheel via a circuit. 

While some riders report battery level increases while going downhill, the thought of simply reversing current through the main board to the battery seems unlikely if not hazardous.

There are no mechanical brakes or separate braking resistors in the wheels. At one point, I was wondering if the wheel would actually just dissipate everything in the mosfets or use battery power to decelerate by switching the magnets in different order, but that would likely burn things up, as most of it would go into heating the mosfets and the coil wiring.

The first answer in the electronics.stackexchange -question I linked to explains how it works with 1-phase motor, although similar setup should work with 3-phase motors also:  https://electronics.stackexchange.com/a/56187 

The basic idea is that the motor acts as generator and with correct switching, the motor coils are used as a boost-converter to get the back-EMF voltage high enough ( U = L*(di/dt) ?) for the current to flow in reverse through the high-side mosfet, charging the battery. Short circuiting the motor (probably with varying duty cycle PWM-pulses to control the braking power, not continuosly) for a little while over the low-side, which brakes the motor (and heats up the mosfets fast), then release the energy that wasn't burned up as heat but instead got stored in the magnetic fields of the coils through the high-side mosfet (at that point, the back-EMF must be higher than the battery voltage for the current to flow in reverse). 

About a year ago, I hooked up one of the phases of the Firewheel -motor to a half-bridge that was switching the mosfets and transitioning between high- and low-side switching (4kHz PWM, 50% duty cycle, altering between high- and low-side every 100ms), another phase (or was it both the remaining phases, I don't remember anymore) into ground and then spun the motor by hand and turned on the circuit to brake it. I don't also remember what I had as load in the high-side, maybe it was a 9V battery...

fQoYJXv.png

The horizontal grid squares in the middle are when the high side is being switched, even though I was just spinning it by hand, the voltage shoots up pretty high, so definitely boosting :P The motor also stopped pretty fast once the circuit started braking it.

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On 5/9/2017 at 5:56 AM, esaj said:

correct switching

Speaking of switching (topics) it was maybe 2002 when Sinnika retired. She was from Finland. Having worked 3 jobs a day over most of her life in the Boston area, she paid for her house in Roxbury. After retiring she went back to her family in Finland. The head lab director gave her a big retirement party.

Sinnika , shorter woman than I, made 'media and plates' (very much needed) for people in the labs from chemical 'recipes' stored on cards or sheets of paper. When I first met Sinnika the latest Mac was but a modest cube with a screen but only in the possession of the PhDs. Several times a week she would walk into the lab and say 'you know what' and then delve into a conversation. She exchanged letters with someone young (maybe in Africa) and sent them money. She would sometimes ask to have her English phrases corrected before mailing her letter. 

One day she bought the game 'Pokemon' for her relatives kids. She said it was a really popular game with kids. Who knows maybe her family has recently played pokemon-go with her.

It's been over ten years since she sold her house and went back to Finland. One day I was working in the lab alone. She stepped into the doorway and snapped a picture and gave me a copy.

Russians, she once said, 'you can't trust them' as I described a flight sim game called ef2000 (sorry Russian readers).

http://www.csoon.com/issue13/ef2000.htm

Those were strong words from the meek Finnish woman who worked three jobs a day in the Boston area, when she was younger, to buy her house before her retirement caused her to sell and return to Finland. I don't know where though.

The same people threw a departing party for me when I left in 2006. It was much smaller than Sinnika's party.

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13 minutes ago, The Fat Unicyclist said:

You just need to retrofit one of these to your EUC...

images?q=tbn:ANd9GcQfs43Gx0dHNDOM4-qOwBt

In fact, if you connect in 3-4, you would never need to recharge your wheel at all! :huh:

That looks familiar, is that a generator to power the headlight?  Those were so cool!  Tiny generator!  3 or 4 ought to do it.:unsure:  Thanks for bringing back memories.:cheers:

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47 minutes ago, The Fat Unicyclist said:

You just need to retrofit one of these to your EUC...

images?q=tbn:ANd9GcQfs43Gx0dHNDOM4-qOwBt

In fact, if you connect in 3-4, you would never need to recharge your wheel at all! :huh:

Hey....welcome back! Your idea buddy ....I say go for it! The first perpetual EUC!:P

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27 minutes ago, Rehab1 said:

Hey....welcome back! 

Thanks... It's good to be back! 

I had a couple of months of overly frantic work, followed by most of a month in Europe (with bugger-all data available). 

But I'm ready now, and shopping for some P-EUC dynamos.

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3 hours ago, The Fat Unicyclist said:

Thanks... It's good to be back! 

I had a couple of months of overly frantic work, followed by most of a month in Europe (with bugger-all data available). 

But I'm ready now, and shopping for some P-EUC dynamos.

Whoa looky who's back?!  :w00t2:  So did my psychic summoning powahs get you all itchy for some forum participation??? Geez Louise better late than never I guess!

Now if only I could get that Cloud guy back on... EUC Avengers unite!  :clap3:

By the by who's this @The Skinny Unicyclist ?  Any relation?

 

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It seems to me that due to the rather inefficient battery charging system on eucs where only a percentage of the power generated actually makes it into the battery, the rest being removed in the form of heat, it is highly unlikely that any added weight going down hill would increase the power generation sufficiently to offset the extra power required to keep the extra weight upright and balanced.

The power required to balance a euc is considerable and increases with weight, this is why the smal 250w motors used quite effectively on electric bikes are no good for eucs.

It is a basic fact that the best way to improve the performance of your euc is to go on a diet and certainly not carry any extra weight! :)

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2 hours ago, Hunka Hunka Burning Love said:

By the by who's this @The Skinny Unicyclist ?  Any relation?

So, I have a sister... Who visited recently.

Not to see me so much as to learn to ride an EUC (I think). And I also think she now may be our latest convert!

UPDATE: Just confirmed. She is currently waiting on delivery of her KS14D! 

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