Charging supercapacitor

Discussion in 'General Electronics Chat' started by Enc2012, Mar 27, 2013.

  1. Enc2012

    Thread Starter New Member

    Oct 11, 2012
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    Hi.
    I have ordered six supercapacitors just for test.
    Each is 2,4V - 120F.

    As far as i understand supercapacitor uses liquid electrolyte so supercapacitor could be charged as lead acid battery ( partly ) ?

    Details:
    I will connect those 6 supercapacitors in serial and charge them with 12V / 1A charger. If i let them charging for let's say half an hour, can they be charged to bigger capacity then 12W ? Basically, can they be charged like lead acid battery ( at least partly ) ?
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    First you should look in the datasheet and check what the recommended charge current is. Also you can not look at supercaps as common batteries. An by that think you can use battery charger directly to charge them. That will for sure fry them and probably the battery charger also
     
  3. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Capacitor is not a battery so it can't be charged using a battery charger. You will need to make your own or adapt the lead acid charger, and reding the datasheet carefully is a must.

    Also just because they have liquid (more likely polymer) electrolyte doesn't mean they are the same thing as a battery. They are completely different.
     
  4. Enc2012

    Thread Starter New Member

    Oct 11, 2012
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    I agree with you guys but take a look...
    Super capacitor contains electrolyte that base is salt or some weak acid.

    In my opinion there should be some way to charge it ( like i write down, partly ) like battery. The charge will be placed into pores of activated carbon or in graphene and i dont think that all pores are filled after few second of charging ? I know it's just idea but maybe it would work ... ?
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I think you're missing the point here. A battery is an electrochemical devices, and maintains almost the same voltage whether fully charged or fully discharged.
    A capacitor is an electrostatic device, which when empty has zero voltage and when full it has the maximum voltage the dielectric can withstand.

    When you connect an empty capacitor to a voltage source the capacitor acts like a short and the only thing that limits the charging current is the resistance of the wires. This is why charging a supercapacitor with a battery charger will most likely not work and you will end up damagning both the cap and the charger due to overcurrent.

    Second thing is that if you charge the cap to a tiny bit more than what it is rated it will self destruct rather spectacularly. Caps have some tolerances, so when you charge six of them in series with a single supply you have a big chance that one of them will charge faster and exceed that voltage rating before you stop charging.
     
  6. gerty

    AAC Fanatic!

    Aug 30, 2007
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  7. Enc2012

    Thread Starter New Member

    Oct 11, 2012
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    I'm aware of charging process in standard capacitor but i was thinking that this could be different in super capacitor.

    My main idea is to build 230V super capacitor bank that can act like battery system for cca 30 minutes. Output power should be in 50W range.
    Let's take 2.3 / 120F capacitor as example. Fully charged, he can give 1,6 or so Watts, for half hour ( if 1 sec discharge is = to 350W ).
    Hundert sc's should do the trick.

    The reason why i started this thread is configuration and charging options.
    If i connect 100 SC's in serial i will get 230V / 120F but to fully charge this capacitor bank i would have to have real strong charger ?
    How strong?. How is this done in some real life situations ?

    So i was thinking, there is electrolyte inside, maybe some chemical reaction will occur and i could charge it longer but i will get the same charge with smaller charger...
     
  8. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    First, there is no chemical reaction inside the capacitor unless you reverse the polarity or overvolt it.

    50W over 30 minutes is 90kJ of energy, however as soon as you start to draw power from the bank the voltage will start dropping linearly with time, so you will need some stepup converter to cope with that.

    Charging depends on how fast you want to charge them, faster needs higher current. And like i said before, a bank of consisting of lots of caps in series will need some monitoring circuit to prevent overcharging and reversing polarity on the caps that would destroy them, so if you take into account that you need a stepup anyway it boils down to having them in parallel.
     
  9. gerty

    AAC Fanatic!

    Aug 30, 2007
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    For the price of all those capacitors and inverter, you could buy a generator...
     
  10. PackratKing

    Well-Known Member

    Jul 13, 2008
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    120 Farad ?? :eek: Be careful w / them things dude...
    even @ 24 ? volts they will flat light up yer life fer an instant before they kill you... :rolleyes:
     
  11. crutschow

    Expert

    Mar 14, 2008
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    A supercapacitor is just a large capacitor and has little similarity to a battery. It's immaterial how the capacitance is physically generated, it still needs to be treated as a capacitor.

    If you want something to act like a battery, then use a battery, not a supercapacitor.
     
  12. Enc2012

    Thread Starter New Member

    Oct 11, 2012
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    You are right the prize is quite big but when i look at stuff that i will gain by using this setup, then it's better to go this way.

    I was wondering, how to prevent fast discharge.
    Equipment that should be powered by this capacitor bank, should not draw more then 15% of rated power. So it can draw max 60 W.

    If something goes wrong, how can i disable capacitor bank to make fast discharge ?. Discharge should always ( start / work time / stop ) be in 50-60W range and anything bigger then this, will destroy the equipment.

    ------------------
    I'm afraid of that but there must be a way to prevent this ?.

    Monitoring circuit will be developed but i'm not following you regarding step up part.
    Why would i need stepup when i can create some 220 AC / DC converter and charge them when its needed ?
    Maybe i got it wrong :) Sorry in advance...
     
    Last edited: Mar 27, 2013
  13. bug13

    Well-Known Member

    Feb 13, 2012
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    if you want to use it as a battery, you want your battery to remain at around 230V as long as it can, but as a cap, it's voltage will drop at a rate of 63% per time constant, and you don't want that.

    without an step up converter, this is very poor performance battery.

    And, make sure your safety procedures are in place:)
     
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