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Ex train super caps maxwell

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antiscab
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Real Name: Matthew Lacey
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Ex train super caps maxwell

Post by antiscab »

Not mine, but saw on facebook in Melbourne

https://www.facebook.com/groups/2979133 ... 2/?sfnsn=m
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

T1 Terry
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Re: Ex train super caps maxwell

Post by T1 Terry »

Hi Matt, how do you calculate the equivalent Ah capacity or Wh from each of these 48v capacitors?

T1 Terry
Green but want to learn

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coulomb
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Re: Ex train super caps maxwell

Post by coulomb »

T1 Terry wrote:
Mon, 13 Apr 2020, 12:27
how do you calculate the equivalent Ah capacity or Wh from each of these 48v capacitors?
I'd say energy E = ½CV² (Joules) = (1/7200)CV² (Wh) (C is capacitance in farads, V is voltage in volts).

Then take off a generous 20% for the capacitors, because you usually can't efficiently get the last bit of energy out of them, since it's at a fraction of a volt. But by this point, the energy storage is usually soberingly low.

Edit: Ah doesn't really make sense for capacitors, since their voltage is so variable.
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antiscab
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Re: Ex train super caps maxwell

Post by antiscab »

I'd say these caps are only any good in a hybrid application
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

T1 Terry
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Joined: Thu, 30 Sep 2010, 20:11
Real Name: Terry Covill
Location: Mannum SA

Re: Ex train super caps maxwell

Post by T1 Terry »

Sorry for the dumb questions, but the 48v mentioned as the base block voltage, is that peak or nominal? Do capacitors even have a nominal voltage?
I thought capacitors were not intended to be run near their rated voltage so if the rated voltage is 48v per pack, what would a sensible running voltage be?
I was looking at the possibility of using these supercaps with a smaller capacity battery pack for the big bus project. As a capacitor can handle a rapid recharge and discharge, they would be better suited for the long regen on the down hill runs and that full power burst required ever so often where batteries along would suffer a serious voltage sag and a faster loss of cycle life.

T1 Terry
Green but want to learn

antiscab
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Re: Ex train super caps maxwell

Post by antiscab »

absolute max voltage is 51v. 48v is as high as I would go, to keep some margin
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

T1 Terry
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Posts: 1108
Joined: Thu, 30 Sep 2010, 20:11
Real Name: Terry Covill
Location: Mannum SA

Re: Ex train super caps maxwell

Post by T1 Terry »

Thankyou Matt, that gives me a figure to work from with 48v being the upper cut off point. Now to work out the battery pack size working backwards using an upper limit for the cells well in the safety zone for both capacitors and cells.

T1 Terry
Green but want to learn

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