# capacitors in you bike?????



## mattW (Sep 14, 2007)

They aren't needed and its pretty tricky to get the energy out of. It cheaper, easier and tried to just go with batteries.


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## Little Rhody (Jun 17, 2008)

Why would it be tricky to get the power out of them? 

LR


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## mattW (Sep 14, 2007)

Because of the way they deliver their power. The current delivered is proportional to the rate of change of voltage so you can get a constant current out but the voltage just linearly declines to zero. On the motor you need the voltage to increase with rpm not the other way around, so you'd need some clever circuits to make better use of them. If used in parallel with batteries the rate of voltage sag of the batteries will determine the current out of the capacitors.


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## frodus (Apr 12, 2008)

there are already some capacitors in the controller.... but you can add more if you want. All its going to do is allow you to peg the throttle and keep from hammering your batteries as hard.... its a buffer. This could in turn get you A TINY BIT more range, because you're being a little more gentle to them, and the peukert effect is decreased.

Just putting some on and using those for the controller won't work either. In order for you to get the power you want out of them (for very long) you'd need high voltage caps and a controller that is functional from that high voltage, down to almost nothing. Finding circuitry that can do that efficiently is a challenge, which is why you don't see alot of people putting caps in. Some install a cap pack though, as a buffer.


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## Little Rhody (Jun 17, 2008)

frodus said:


> there are already some capacitors in the controller.... but you can add more if you want. All its going to do is allow you to peg the throttle and keep from hammering your batteries as hard.... its a buffer. This could in turn get you A TINY BIT more range, because you're being a little more gentle to them, and the peukert effect is decreased.
> This is what I had in mind. I wasnt trying to replace the batts with caps, just wanted to add some for a strain protection.
> 
> Just putting some on and using those for the controller won't work either. In order for you to get the power you want out of them (for very long) you'd need high voltage caps and a controller that is functional from that high voltage, down to almost nothing. Finding circuitry that can do that efficiently is a challenge, which is why you don't see alot of people putting caps in. Some install a cap pack though, as a buffer.


Thanks for you input,
LR


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## major (Apr 4, 2008)

Hey anybody,

I have a picture of an electric bike with NiCad batteries and ultracpacitors I thought I'd post up here. But I can't figure out how to do it. It won't allow me to paste it. And I don't see any help menu for "forum dummies".

Any help from forum experts is appreciated.

major


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## mattW (Sep 14, 2007)

If the image is hosted elsewhere right click and click 'copy image location' and then the little yellow insert image button with the mountains just above where you are typing in the text window and paste the link.

If its on your computer click on 'go advanced, just under where you are typing and click to add an attachment, just under the typing window.

Hope that helps.


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## Little Rhody (Jun 17, 2008)

major said:


> Hey anybody,
> 
> I have a picture of an electric bike with NiCad batteries and ultracpacitors I thought I'd post up here. But I can't figure out how to do it. It won't allow me to paste it. And I don't see any help menu for "forum dummies".
> 
> ...



OOOO............ Gimmy Gimmy Gimmy...............
I want to see the pic. please get this posted. 

Thanks LR


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## major (Apr 4, 2008)

mattW said:


> If its on your computer click on 'go advanced, just under where you are typing and click to add an attachment, just under the typing window.
> 
> Hope that helps.


Thanks, mattW,

I'll try that.

O.K. So where is "go advanced? Yeah, it's a picture on my computer.

major

Guess it worked. Not real great, but my first attempt. At posting a picture, that is.

major


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## frodus (Apr 12, 2008)

They're great at handling the instantanious demands of the controller...

I wasn't sure if you wanted to use them as the only source, or in parallel.

If you decide to do it, please document it and let us all know, there's not a ton out there of Emotos with caps on them.


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## Little Rhody (Jun 17, 2008)

frodus said:


> They're great at handling the instantanious demands of the controller...
> 
> I wasn't sure if you wanted to use them as the only source, or in parallel.
> 
> If you decide to do it, please document it and let us all know, there's not a ton out there of Emotos with caps on them.


Will do...... I like this idea, and cant think of any negative side to it, other than space requirements maybe. 

LR


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## frodus (Apr 12, 2008)

hell, give me a little time, and I might put a big bank on  It'd help with voltage sag too, since the bats aren't being drained by peak currents.


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## Little Rhody (Jun 17, 2008)

Here is one I just found, not heavy enough for the Sepex motor I want to run, but this might help someone. Good price too. 
http://cgi.ebay.com/AEROVOX-CGS-CAP...276176QQcmdZViewItem?IMSfp=TL0806011452r36330

LR


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## frodus (Apr 12, 2008)

not one of them, put a bank of them in there.


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## Little Rhody (Jun 17, 2008)

frodus said:


> not one of them, put a bank of them in there.


Well those are rated at 350A, my motor is rated at 450A, I would need at least 500A caps. How many should I run? as many as I can fit? one per batt? should I have an even number of them? 


LR


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## frodus (Apr 12, 2008)

you're mixing up volts and amps... the caps are 350V... they'll be fine as long as you don't go over 350V... As far as amps, you'll only suck the amps out of the caps as fast as they deliver. Once they're done supplying extra current, they just sit there discharged, until they can equalize off the batteries. Its not you're ONLY source for current. they aren't in series with the battery pack, you'll have a pack of caps in parallel with the batteries. I assure you it works just fine. We've got 20 or so small caps, 200V or so, and the controller we're developing puts out 350A on the motor side, with ~80V on the input side. This is done not moving, full throttle with the brakes on full. You need to sit down and calculate out what Farad and voltage cap you need... do some research on chosing capacitors.

The motor may be 450A, but I HIGHLY doubt you'll be supplying that much on the battery side of things. 

I think you need to research a little more on some electronics theory... it might help in understanding what you should do if you understand how the controller and the caps are working.


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## Little Rhody (Jun 17, 2008)

frodus said:


> you're mixing up volts and amps... the caps are 350V... they'll be fine as long as you don't go over 350V... As far as amps, you'll only suck the amps out of the caps as fast as they deliver. Once they're done supplying extra current, they just sit there discharged, until they can equalize off the batteries. Its not you're ONLY source for current. they aren't in series with the battery pack, you'll have a pack of caps in parallel with the batteries. I assure you it works just fine. We've got 20 or so small caps, 200V or so, and the controller we're developing puts out 350A on the motor side, with ~80V on the input side. This is done not moving, full throttle with the brakes on full. You need to sit down and calculate out what Farad and voltage cap you need... do some research on chosing capacitors.
> 
> Thats me trying ti multi task, (work and play at the same time) good catch.
> 
> ...




I am no electrical engineer by any means, and can always use all the help I can get. Yes I do need a bit more research. It is just so easy to ask quest dumb or not. 

Thanks,
LR


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