seperate regen braking system?

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jimmyhackers   100 W

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seperate regen braking system?

Post by jimmyhackers » Mar 15 2019 3:13pm

do they exsist for brushless hub motors?

im thinking of making something that adds breaking force and generates 12v for brake lights and other systems.

if it already exsists and is cheap enough id rather buy it.

TIA
jim
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amberwolf   100 GW

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Re: seperate regen braking system?

Post by amberwolf » Mar 16 2019 3:28am

You do realize that continuously taking power from the forward motion of the bike to run the lights is going to slow it down, and energy regained that way is wasting more than you get back, because of all the conversions from battery to controller to motor to controller to battery, unless you were trying to stop.

So running your lights off of forward motion will just drain your batteyr faster than just directly running the lights off the battery (even via a DC-DC).

There's a lot of threads on this kind of thing.



That said: No, there are no separate systems available to do just braking / regen, that you could hook up to a motor that's already being used by a controller as a motor.

You can design and build something if you like, and there are threads discussing the problems of switching back and forth between traction controller and braking controller, but it's WAY WAY less complicated to just get a cotnroller that does regen in the first place (especially since the easiest way to get a separate regen braking system is to just use a regen-capable controller...which if you already have it, you should just use it as the only controller).


If you want you can use a separate motor as a generator to run the lights, but it's simpler to just by a dynamo hub wheel. Of course, either of these solutions is just another version of the problem noted at the start of this post--you're just wasting power out of your battery. It probably wastes less power to just use giant resistors to drop the battery voltage down to whatever the lights run on, and directly run them off the battery (rather than using a DC-DC).

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dogman dan   100 GW

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Re: seperate regen braking system?

Post by dogman dan » Mar 16 2019 7:19am

Old school bike lights sometimes had a 12v generator that rubbed on the side of the tire to power lights. The drag they created was incredible.

https://www.ebay.com/sch/i.html?_from=R ... e+bike+gen

These days, if you go with led lights, they will run a very long time off of a separate 12v battery that doesn't have to be very big.

If you are looking for just a headlight, lots of good led light options, that are if anything, too bright, and run on 3v -6v.

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jimmyhackers   100 W

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Re: seperate regen braking system?

Post by jimmyhackers » Mar 18 2019 1:48pm

thanks for the info.

at the moment im turning my braking energy into heat with no recapture at all :s

i did think about a 12v dyno on the brake arms but it seemed a bit convoluted.

i think i wasnt clear on exactly what kind of system i had in mind.

it will either be a set of super caps or a small 12v battery thats charged up by braking force. you would have to connect up the motor phases into a rectifier then a dc-dc step down transformer into the 12v battery. but only have this conected/working when the brake lever is pulled.

i already use a dcdc step down transformer for turning 72v into 12v for my headlight n horn. so the rest is just diodes, wires and relays.

the benfit i see to this over a normal regen is that a seperate 12v system instead of main battery recharging would be able to use more of the avaialble braking energy.

but you are probably right. im better off seeing if mine does regen (wires are labeled so poorly) and if not getting a controller that does if i really want it enough.......

thanks for the help
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Re: seperate regen braking system?

Post by billvon » Mar 18 2019 1:58pm

jimmyhackers wrote:
Mar 15 2019 3:13pm
do they exsist for brushless hub motors?
Sure. Any brushless direct drive hub motor can be a generator. You can either use the existing functionality in the controller or build a regen-only circuit. A very simple way to do it is to use 3 H-bridges to short all phases simultaneously and periodically (say at 50KHz) and then vary the duty cycle to get the braking you want. You recover the energy through the body diodes, or separate diodes if you want better efficiency.
--bill von

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