On Feb 23, 5:49*pm, Tim Streater wrote:
In article
,





*harry wrote:
On Feb 23, 11:21*am, The Natural Philosopher
wrote:
http://en.wikipedia.org/wiki/Super_c...#Disadvantages
which says

- The amount of energy stored per unit weight is generally lower than
that of an electrochemical battery (3–5 W·h/kg for a standard
ultracapacitor, although 85 W.h/kg has been achieved in the lab[4] as of
2010 compared to 30–40 W·h/kg for a lead acid battery), 100-250 W·h/kg
for a lithium-ion battery and about 1/1,000th the volumetric energy
density of gasoline.

This alone rules out supercapacitors for any practical use as car batteries.

- Has the highest dielectric absorption of any type of capacitor.
- High self-discharge – the rate is considerably higher than that of an
electrochemical battery.
- Low maximum voltage – series connections are needed to obtain higher
voltages, and voltage balancing may be required.
- Unlike practical batteries, the voltage across any capacitor,
including EDLCs, drops significantly as it discharges. Effective storage
and recovery of energy requires complex electronic control and switching
equipment, with consequent energy loss.
- Very low internal resistance allows extremely rapid discharge when
shorted, resulting in a spark hazard similar to any other capacitor of
similar voltage and capacitance (generally much higher than
electrochemical cells).- Hide quoted text -

http://en.wikipedia.org/wiki/Super_capacitor#Vehicles
You didn't read far enough down the page.

So which precise bit of that says they have a practical application in
cars?

The very first paragraph.