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GB: Australia Ultra-Capacitor *Collecting Money*

bobhaha

bobhaha

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5A max at 30V.

Yeah I'm going to upgrade the alligator clips once the caps show up. If I charge at a constant voltage of 10V I would expect 5A to be fine going through these clips... is that right?

I power my laptop at 2A 19V for more than 6 hours at a time with no problems. Do you think I should invest in a car battery charger?
 





Fiddy

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the caps will want to pull way more than 5A from the supply from when charging so your supply will be maxed out for the whole charge until it starts to drop off at the end as each cap approaches 2.7V.

Im using a 10A 30V Variable power supply and some 1.5mm2 lighting circuit cable to charge mine and im dropping 0.6V on the cable at 10.6A.

I used alligator clips the first time and it was dropping so much current it melted the insulation away from the clip after a while lol the cable is pretty small in those leads im guess they are like 0.5mm2.

You will probably want something with more grunt
ive got this: Digital Adjustable Variable DC Power Supply 30V 10A S 3010D BLUE LED | eBay
 
bobhaha

bobhaha

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Or I could get a 12V car battery charger @20A for like $60 at Bunnings.

I guess I'll just have to see if it works or not with the PSU I have here.
 
Fiddy

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you can do that, but you will find you will have balancing problems when charging in series
 
bobhaha

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Why so? What would be the difference between your 10A PSU and my 5A PSU?

You know they are limited.... even if it wants to draw more than 5A it can't.
 
Fiddy

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There will be no difference in balancing the capacitors on the 5A or 10A PSU.

The capacitors aren't all the same capacitance, some will charge faster than others, so there is potential to overcharge a single cap in the bank, but if you stay away from your 13.5Vmax then you should be good, just check each capacitor in the bank to make sure they are close enough in voltage when charging.
 
LaZeRz

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Hmm, I can't find any 2.7 volt or lower chargers at home so do you think that charging with 5v and metering the voltage would work? I've seen people charge it like that but im not too sure if its safe. I don't want this thing blowing up.
 
Fiddy

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Sounds like a job for a voltage regulator circuit :)
you could use some resistors to setup a series voltage drop too
 
LaZeRz

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Ikr, I guess I'l just finish off my PSU, I really can't be bothered doing crap atm tho :p I've had a tiring week...
 
bobhaha

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Finished my cap bank!!! YAY!!

IMAG0777.jpg


IMAG0778.jpg


IMAG0779.jpg
 
bobhaha

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Not yet.... literally just finished them...

Do you recommend that I charge them to 10V first? Just in case they become imbalanced? That will give you ~2V per cap.
 
Fiddy

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yep thats a good idea, the first time i charged mine i was checking each cell every so often.

some formulas for charge time and rates:


Max energy = 0.5 x C x Vsquared = joules


Capacitors In series Capacitance = 1/ (1 / C1) +(1/C2) + (1/C3)
Vtotal = V1+V2+V3


Charge Rate = Charge Current / Bank Capacitance= (mV/Second)


Charge Time (seconds) = Vtotal / (mV/Second)

---------------------------------------------------------------------------------------------------------------------------

So you will be looking at:


5 x 2.7V = 13.5Vtotal

1 /3000 = 0.003333
1 / (0.003333 x 5) = 600 Farad

0.5 x 600 x (13.5x13.5) = 54,6750 joules

say 5A charge current:

5A / 600 Farad = 0.008333V per Second

13.5Vtotal / 0.008333V = 1620 seconds /60 = 27mins
 
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bobhaha

bobhaha

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Cool and at 10V I'll be looking at only 20min charge time. Nice! I'll charge these up soon!!!
 
Fiddy

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yup :)

make sure your supply leads aren't too small cause they will increase the charge time cause current will be wasted on them.
 
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