# 550m descent, regen needed



## remy_martian (Feb 4, 2019)

20W/kg is about right, based on my car descent experience on almost the same exact incline. 10W/kg is not enough braking and it speeds up. 

Approximation only...


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## evVanagon (11 mo ago)

I'd recommend Grin Technologies All-Axle Front Hub Motor that's made up here in Canada. All-Axle Hub Motor - Grin Products - Product Info. I use it on a bakfiets like yours.

The Cycle Analyst is a HUD display that lets you program the controller and has a ton of settings. https://ebikes.ca/documents/CycleAnalyst_V31_Web.pdf. Their controllers have variable regenerative braking and can be tied to your throttle when an e-brake is fitted so you can increase/decrease the amount of regen on the fly. (pg. 27) Automatic braking is possible by setting a speed limit and that speed limit can be tied to a separate handlebar up/down control. (pg. 19)

Personally, I haven't tested auto-regen all that much as I don't have the hills, but I'd appreciate a video.


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## dedlast (Aug 17, 2013)

Here's an odd thought that I'm not sure how you would make work. Somehow switch the motor leads over to a healthy resistor bank for the downhill portion of your trip. Similar to how railroad locomotive dynamic braking works. You would need to do the math to figure out how much resistance and what wattage rating to use for the resistors.

https://en.wikipedia.org/wiki/Dynamic_braking 

B


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## remy_martian (Feb 4, 2019)

20W/kg

Add a bathtub to the rig to cool your resistor?

It's a mountain. Dumping into a resistor is pointless for tye amount being spent. Assist on the climb home is nice, even better when you're coming home empty.


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## EV_Jibareaux (Nov 10, 2019)

torrin said:


> I'd recommend Grin Technologies All-Axle Front Hub Motor that's made up here in Canada. All-Axle Hub Motor - Grin Products - Product Info. I use it on a bakfiets like yours.


good link and good info, thanks. The new build is not for the bakfiets, it's a suspended carbon fiber frame. I'm not a fan of front wheel drive on a bike, throttling out of corners is off balance with the center of torque in front of me.


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## EV_Jibareaux (Nov 10, 2019)

dedlast said:


> Here's an odd thought


you're correct in that but the type of motor is not the same. Big old motors with brushes can have the polarity reversed to generate brake power, bikes/scooters use BLDC motors, to dynamic brake is done by changing the timing of the signal sent to the motor. Same result, electricity makes go into whoa.


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## remy_martian (Feb 4, 2019)

No. You are wrong.

Yes you can reverse polarity on a DC, but you are using electical energy to counter potential energy. By your method you use 2 times X joules to leave and get back.

If you stored the energy in a battery going down hill using REGEN, you'll get back around 70% of the energy needed to climb the hill.

So you can use 2X or 0.3X energy. Over six times the energy expended to do reverse polarity braking than to regen. Your pedal power goes down by 3 times to climb back up.


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## EV_Jibareaux (Nov 10, 2019)

remy_martian said:


> No. You are wrong.
> Over six times the energy expended to do reverse polarity braking than to regen.


Maybe it's a language barrier but as you may recall from my OP I need the electrical power for braking & regen seems to be the only retail option. I really don't want to build a custom controller . 

I also need rear wheel power as I indend to put 3kw on the frame with a triple tree suspension fork, the headset bearings won't operate properly with that kind of torque.


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## remy_martian (Feb 4, 2019)

Again - you want to store the energy from the hill in a battery, then use that stored energy to help climb it. 

Almost any brushless motor controller will regen to do this. 

You'll need around a 1kWh battery pack to store and release the energy.

Your motor sizing sounds about right for a 150kg bike and payload (includes rider).


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## EV_Jibareaux (Nov 10, 2019)

remy_martian said:


> Again - you want to store the energy from the hill in a battery, then use that stored energy to help climb it.


No, that's not what I want. 

Estaré a plena carga al comenzar mi ascenso.

No necesito la recarga para asistirme en mi ascenso, necesito potencia de frenado para controlar mi descenso.


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## dedlast (Aug 17, 2013)

EV_Jibareaux said:


> No, that's not what I want.
> 
> Estaré a plena carga al comenzar mi ascenso.
> 
> No necesito la recarga para asistirme en mi ascenso, necesito potencia de frenado para controlar mi descenso.


My concern, not too clearly stated above, is that he could/would reach charge capacity of the batteries on the down hill ride and suddenly have no regen available. From the comment above, it sounds like he starts at the bottom fully charged and then comes back down. Granted, there would be room for some charge since he went up first, but there is the real possibility that he could overcharge coming back down. At least in my opinion, the way I see it, for whatever that's worth.

B


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## TeZla (Feb 18, 2021)

Remy es un idiota maleducado. cree que lo sabe todo, pero a menudo se equivoca


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## remy_martian (Feb 4, 2019)

That fourth word is Latin-based, as is the English language. 

On the Internet, there are characters, then there are the people behind them. Learn to figure out which is which.

Your lessons for the day.


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## remy_martian (Feb 4, 2019)

dedlast said:


> My concern, not too clearly stated above, is that he could/would reach charge capacity of the batteries on the down hill ride and suddenly have no regen available. From the comment above, it sounds like he starts at the bottom fully charged and then comes back down. Granted, there would be room for some charge since he went up first, but there is the real possibility that he could overcharge coming back down. At least in my opinion, the way I see it, for whatever that's worth.
> 
> B


That would violate the laws of physics unless he pedaled on the way up


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## TeZla (Feb 18, 2021)

remy_martian said:


> That fourth word is Latin-based, as is the English language.
> 
> On the Internet, there are characters, then there are the people behind them. Learn to figure out which is which.
> 
> Your lessons for the day.


Why would I ever take a lesson from a fool?

If you have a problem with google translate, take it up with google. I merely use the tool available


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