Help please. Super capacitors as an alternative for battery.

Discussion in 'The Projects Forum' started by Macky Buenaflor, Feb 25, 2016.

  1. Macky Buenaflor

    Thread Starter New Member

    Feb 25, 2016
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    Hello all. I'm new here. I was wondering on how can we exhaust more the use of supercapacitor module (48V, 165F) on an electric bicycle with a motor rating of 350W, 48V battery, 30-35kph max speed. After replacing the battery with our supercapacitor, the e-bike worked fine but upon reaching 43-42V, starts slowing down until the motor finally stops at 41.7-41.9V. Is there a way on each we can drain the remaining energy of the supercapacitor (e-bike continues to drive) for at least lower than 10-30V? Is there an electronic circuit or device that we can buy (or create) online? Thank you so much! Really hoping for a solution. :)
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
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    It sounds like your controller turns off at 42 volts - probably to save the batteries you don't have any more. :D
    You could use a boost converter to raise the voltage, but it might be easier (cheaper) to build your own controller.
     
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  3. Macky Buenaflor

    Thread Starter New Member

    Feb 25, 2016
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    Sorry to ask you for this, but could i ask for your help in knowing the specs and components that we would need here? Like knowing this is a 165 F supercapacitor, which would mean having 165A/s, what value of resistor should we use?
     
  4. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    The best way to use the SC is in a regenerative braking arrangement; Put the battery back in and use the SC to store energy during braking so that it can be used to assist the battery when accelerating.
     
    Last edited: Feb 25, 2016
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Your voltage won't last very long no matter what you do. Just a few seconds.
     
  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    I would not put my own money behind this, but found on eBay a 1200 W 20A input max. constant current , constant V boost convertor, seller # 10546. Should supply 48 V @ 7 A down to about 17 V on Cap. How long ??
     
  7. RamaD

    Active Member

    Dec 4, 2009
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    The Cap when charged to 48V has the energy to support 350W discharge for about 9 mins, leaving all losses. At 42V it is for 7 mins. So discharging upto 42V should give a run time of 2 mins, if entire 350W is being used. However, this leaves quite a bit of energy left in the cap.
    At 16V, it is left with only 1 min. of run time left. 48V to 16V gives a run time of 8 mins. that is almost 89% of total energy. All this give some kind of ball park figures to work with.
    This is assuming that there are no losses and being discharged at 350W, which is probably not the case all the time. Lower discharge would give more time.
    I would go by Bernard's suggestion of boost converter. There would be losses of the converter. One issue I see is, Initial surge current may not be supplied by the converter, which could shutdown or acceleration could be slow.
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    A little pedal power for initial start should extend running time.
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    batteries, if rated like super caps, would leave then in the dust as far as storeage goes. super caps are made for smoothing supplies to loads, not supplying power for long times. super caps were first used to smooth the power to base thumper amps in the trunks of cars to compensate for voltage drop through the wire to the battery.
     
  10. wayneh

    Expert

    Sep 9, 2010
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    Super caps are inferior to batteries on energy density per unit of cost or per unit of volume, and possibly even per unit of weight. They also drop voltage as the energy is released far more than batteries do. I see no role for them on an e-bike except perhaps to increase the efficiency of regenerative braking as noted in #4.
     
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