Have you used super capacitors?

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keithg
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Joined: 06/04/2008
Points: 4

I have a Razor MX 650 that my kid likes to ride. I am in the process of converting it from 36v to 48v and am replacing the 36v controller with a 48v 50amp controller (the motor is a unite 750 watt I think). So basicly I will run the motor overvolted. Apparrently others have done this with easy success, if the motor fries I will replace with a larger motor.

Here is my question:

I have been reading a lot about super capacitors and was wondering if anyone has used one (or more) attached to the + battery lead to give an extra power boost on accelleration. Lots I do not know here - can the controller handle it? Does it provide any benefit? How many farads should the capacitor be? And, I'm sure, many other questions yet to be created by others here with more experience than I.

Would welcome any and all help on this - Thanks!!

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deronmoped
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Joined: 12/25/2007
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Re: Have you used super capacitors?

Super Caps could have been a solution for my bike. What happened with my bike was I got the PingPing lithium pack of 20Ah 24V and it would cut out as Ping's batteries are not rated to put out the peak current I needed. I modified the shunt and that fixed it, but if I had a super cap I could have gotten the cheaper 10Ah 24V pack. A super cap would allow the use of a cheaper battery solution, but the super cap would have to be cheap enough to make it a total cheaper solution.

Deron.

keithg
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Joined: 06/04/2008
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Re: Have you used super capacitors?

Thanks for your feedback, any ideas on my other questions?

LinkOfHyrule
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Re: Have you used super capacitors?

I've played around with a few, and can tell you that you'd need a very big, very expensive supercap to do it.

Even 24V is very high for a supercap. The ones I have are only good for 2.3V and 2.5V. The 50F one is a little smaller than a sub-c cell, and can run a tiny toy motor for about 5 minutes at no load, and even then that's running it completely dead ('til it won't move at all). Compare this to a similar size battery that will do the same thing for hours. That one cost me I think $20. You'd need ten to run a 24V motor, and since the discharge curve on a capacitor is a straight line, you could only use the top 5V or so of that.

Until we find out the deal on the EEStor caps, I wouldn't even bother. Even the best lithium you can buy will be far, FAR cheaper; it's been a while since I got these, so the price may have come down, but I paid about $400w/hr for my supercap. Not to mention an equivalent battery will be incomparably lighter and smaller. :/

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chas_stevenson
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Re: Have you used super capacitors?

LinkOfHyrule wrote:

I've played around with a few, and can tell you that you'd need a very big, very expensive supercap to do it.

Even 24V is very high for a supercap. The ones I have are only good for 2.3V and 2.5V. The 50F one is a little smaller than a sub-c cell, and can run a tiny toy motor for about 5 minutes at no load, and even then that's running it completely dead ('til it won't move at all). Compare this to a similar size battery that will do the same thing for hours. That one cost me I think $20. You'd need ten to run a 24V motor, and since the discharge curve on a capacitor is a straight line, you could only use the top 5V or so of that.

The problem with capacitors is when you connect them in series to increase the voltage, the capacitance drops. If you put 10 - 2.5-volt 50F caps in series you get a 25-volt 5F capacitor. To keep the capacitance at 50F you would need 100 capacitors, at $20.00 each ($2000.00). You would be better off buying another battery pack and place it in parallel with your current pack to increase the maximum current draw and at the same time give you more range.

Grandpa Chas S.

keithg
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Joined: 06/04/2008
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Re: Have you used super capacitors?

OK folks,

Thanks for all the great feedback, lots of stuff I did not know. I will put that idea to rest until we humans evolve our technology a bit more.

Keith

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