Highest energy cap that's available in hobby volumes .. maybe a few hundred pieces

[[email protected]]

What's the highest energy cap available and it's source?

The most cost effective?

where energy is the product C * V^2

 

[Phil Allison]

** Groper alert !

What's the highest energy cap available and it's source?

The most cost effective?

where energy is the product C * V^2

** How about 1215 joules for 113 UK pounds ?

http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=4704897&N=401







........ Phil

 

[Eeyore]

What's the highest energy cap available and it's source?

The most cost effective?

where energy is the product C * V^2

1/2 C * V^2 in fact.

Storing energy at high voltage is best since a caps's size is determined by the
CV product wheras energy is prop to V^2.

Graham

 

[Paul E. Schoen]

What's the highest energy cap available and it's source?

The most cost effective?

where energy is the product C * V^2

Maxwell has BCAP1200-E270 which is 1200 farads at 2.7 VDC, for about $45.40
in quantity of 1 to 99. That's 4374 joules. A bank of 27 in series will
provide 33 farads at 72 VDC, which is enough energy to absorb (or supply)
13 kW for 5 seconds (for EV acceleration and braking) at a cost of $1226.
Still not a replacement for batteries, but perfect for high current surges.
These ultracaps (BoostCaps) have an ESR of only 0.8 uOhms and peak current
of 3750 amps. They are about 3" long and 2.5" dia, and weigh about 3/4 lb.
I received this quote recently.

Check www.maxwell.com for more info. They have 650 to 2600 farads in this
series.

Paul

 

[[email protected]]

What's the highest energy cap available and it's source?

The most cost effective?

where energy is the product C * V^2

i agree with you

 

[Spehro Pefhany]

1/2 C * V^2 in fact.

Storing energy at high voltage is best since a caps's size is determined by the
CV product wheras energy is prop to V^2.

Graham

I think the volume of the required dielectric is proportional to the
maximum energy stored, assuming a constant volts per mil dielectric
breakdown rating.


Best regards,
Spehro Pefhany

 

[Eeyore]

I think the volume of the required dielectric is proportional to the
maximum energy stored, assuming a constant volts per mil dielectric
breakdown rating.

Best regards,
Spehro Pefhany

Surely the thickness of the dielectric would be prop to voltage ? Hence size > CV
whilst energy > 1/2 C*V^2.

This certainly what I've found.

Graham

 

[Spehro Pefhany]

Surely the thickness of the dielectric would be prop to voltage ?

Yes, let's say. But capacitance is prop to 1/thickness.

Hence size > CV >whilst energy > 1/2 C*V^2.

Okay (parallel plates, ignore edge effects)

capacitance = e * A/t where a is the area and t is the distance
between plates and e is the permittivity.

t = k * V, where V is the maximum operating voltage and 1/k is the
dielectric breakdown voltage in volts/unit thickness

(Max) Energy = (1/2) * V^2 * e * A/t = (1/2) * V * e* A/k

we also have dielectric Volume = t * A = k * V * A

so (Max) Energy/Volume = e/(2*k^2), a constant dependent only on
dielectric characteristics

I also think this makes sense intuitively.

This certainly what I've found.

Graham

Best regards,
Spehro Pefhany

 

[John Larkin]

Yes, let's say. But capacitance is prop to 1/thickness.


Okay (parallel plates, ignore edge effects)

capacitance = e * A/t where a is the area and t is the distance
between plates and e is the permittivity.

t = k * V, where V is the maximum operating voltage and 1/k is the
dielectric breakdown voltage in volts/unit thickness

(Max) Energy = (1/2) * V^2 * e * A/t = (1/2) * V * e* A/k

we also have dielectric Volume = t * A = k * V * A

so (Max) Energy/Volume = e/(2*k^2), a constant dependent only on
dielectric characteristics

I also think this makes sense intuitively.



Best regards,
Spehro Pefhany

The size proportional to CV is sort of true in electrolytics, but
obviously not in film caps. Only a small part of a 'lytic is the
actual dielectric, and most of it is carrier foil and
electrolyte/spacer.

John

 

[[email protected]]

1/2 C * V^2 in fact.

As a minor nit ... the 1/2 is necessary only to scale the product into
joules units, the base equation is the fundamental equation for
capacitance and voltage representing energy.

 

[[email protected]]

Maxwell has BCAP1200-E270 which is 1200 farads at 2.7 VDC, for about $45.40
in quantity of 1 to 99. That's 4374 joules. A bank of 27 in series will
provide 33 farads at 72 VDC, which is enough energy to absorb (or supply)
13 kW for 5 seconds (for EV acceleration and braking) at a cost of $1226.
Still not a replacement for batteries, but perfect for high current surges.
These ultracaps (BoostCaps) have an ESR of only 0.8 uOhms and peak current
of 3750 amps. They are about 3" long and 2.5" dia, and weigh about 3/4 lb.
I received this quote recently.

Check www.maxwell.com for more info. They have 650 to 2600 farads in this
series.

Paul

 

[John Larkin]

As a minor nit ... the 1/2 is necessary only to scale the product into
joules units, the base equation is the fundamental equation for
capacitance and voltage representing energy.

But you did post to Usenit.

John

 

[[email protected]]

Maxwell has BCAP1200-E270 which is 1200 farads at 2.7 VDC, for about $45.40
in quantity of 1 to 99. That's 4374 joules. A bank of 27 in series will
provide 33 farads at 72 VDC, which is enough energy to absorb (or supply)
13 kW for 5 seconds (for EV acceleration and braking) at a cost of $1226.
Still not a replacement for batteries, but perfect for high current surges.
These ultracaps (BoostCaps) have an ESR of only 0.8 uOhms and peak current
of 3750 amps. They are about 3" long and 2.5" dia, and weigh about 3/4 lb.
I received this quote recently.

Check www.maxwell.com for more info. They have 650 to 2600 farads in this
series.

I sent the Maxwell sales link a request for price and availabilty in
hundreds a little over a month ago, and never got a response. Did a
distributor respond with that quote?

I've since been looking at surplus high voltage caps in the fractional
farad range that are also kilojoule, but are about the same cost and
volume. The only advantage is that they can be connected in parallel,
and not have to worry about the balancing voltage divider.

 

[Jim Thompson]

As a minor nit ... the 1/2 is necessary only to scale the product into
joules units, the base equation is the fundamental equation for
capacitance and voltage representing energy.

Methinks the "minor nit" is your brain capacity ;-)

The 1/2 comes from Integral(C*V)dV

...Jim Thompson

 

[John Larkin]

I sent the Maxwell sales link a request for price and availabilty in
hundreds a little over a month ago, and never got a response. Did a
distributor respond with that quote?

I've since been looking at surplus high voltage caps in the fractional
farad range that are also kilojoule, but are about the same cost and
volume. The only advantage is that they can be connected in parallel,
and not have to worry about the balancing voltage divider.

A big array of series/parallel electrolytics, like photoflash caps,
doesn't need equalizing resistors. Electrolytic leakage is nonlinear
enough to balance the voltages nicely. 'lytics don't fail suddenly
like film caps, they just start leaking more.

Check the surplus houses for electrolytic, film, and oil-filled caps.
Cost per joule will be a fraction of new stuff. Around a few
kilojoules, things start to get interesting.

John

 

[Spehro Pefhany]

The size proportional to CV is sort of true in electrolytics, but
obviously not in film caps. Only a small part of a 'lytic is the
actual dielectric, and most of it is carrier foil and
electrolyte/spacer.

John

Sure, I agree. Here are a few from the same Nichicon series:

Voltage Cap Diam Height Energy Volume Energy/Volume
400 22 16 25 1.76 5.02624 0.350162348
35 1000 12.5 20 0.6125 2.45421875 0.249570255
25 1000 10 20 0.3125 1.5707 0.19895588
16 2200 12.5 20 0.2816 2.45421875 0.114741198

Of course, on power supplies, going to a universal (worldwide) input
off-line switcher means you need to squander a lot of the energy
storage capacity of your primary energy storage capacitor (at minimum
input voltage and frequency), so power supply caps may end up not
being that different in size from that required for a linear supply.


Best regards,
Spehro Pefhany

 

[Ancient_Hacker]

What's the highest energy cap available and it's source?

The most cost effective?

Surely you must have some other constraints, such as minimum or maximum
voltage, capacitance, size, weight, PCB'ness, discharge rate? All
significant.

 

[Paul]

I sent the Maxwell sales link a request for price and availabilty in
hundreds a little over a month ago, and never got a response. Did a
distributor respond with that quote?

I received the quote from Frank Dodaro mailto:[email protected]

I've since been looking at surplus high voltage caps in the fractional
farad range that are also kilojoule, but are about the same cost and
volume. The only advantage is that they can be connected in parallel,
and not have to worry about the balancing voltage divider.

Generally I have only seen surplus capacitors about 5000 uF at 400 VDC,

which are 400 Joules each. They are about 3" dia and 6" long. I paid
about
$5 each for them. So the new Maxwell parts are about the same price per

Joule, and are much smaller by a factor 10 or so. The voltage divider
is a
problem. It would probably be a good idea for the manufacturer to have
an
optional built-in bleeder resistor for this purpose.

Paul
Sent via Google because my news server sucks

 

[Ancient_Hacker]

A big array of series/parallel electrolytics, like photoflash caps,
doesn't need equalizing resistors. Electrolytic leakage is nonlinear
enough to balance the voltages nicely. 'lytics don't fail suddenly
like film caps, they just start leaking more.

Oh, joy, a voice of reason. All the old ARRL Handbooks and many other
books specify that you should put equalizing resistors across
electrolytics and diodes too. With a little reflection you can
convince yourself pretty thoroughly that this is a poor idea.
Electrolytics and diodes are kinda like zeners- they'll self-klimit the
voltage across themselves to a value they can handle. If you add
equalizing resistors you're just forcing the undervoltage-formed
capacitors to dissipate more power.

 

[[email protected]]

Methinks the "minor nit" is your brain capacity ;-)

The 1/2 comes from Integral(C*V)dV

Nope ...l didn't specify units, the units less the 1/2 constant are
JimFart units, where two JimFars are a Jewel

err ... joule ...