B
Bret Cahill
- Jan 1, 1970
- 0
How does a capacitor compare with, say, a lead acid battery,
energy/weight?
Bret Cahill
energy/weight?
Bret Cahill
Bret Cahill said:How does a capacitor compare with, say, a lead acid battery,
energy/weight?
Bret said:How does a capacitor compare with, say, a lead acid battery,
energy/weight?
Bret said:Since it takes about 70 watt hours to get a one ton car up to 45 - 50
mph, the _increase_ in conventional battery weight to allow for
regenerative braking is 1 kg.
A conventional capacitor would add three (3) orders of magnitude more
weight, 1000 kg, ONE METRIC TON, to the regenerative system.
Bret said:At least 10,000 psi H2 tanks don't leave a crater in the road when they
rupture.
Bret said:Call up Homeland Security and tell them you want to put 70 watt hour
super capacitors in motor vehicles.
How does a capacitor compare with, say, a lead acid battery,
energy/weight?
Bret said:How does a capacitor compare with, say, a lead acid battery,
energy/weight?
unless defective the battery is more that 5 times better,
probably much more.
John said:Yup. More like 10,000.
John
Bill said:Honda has an 8 farad capacitor charged to 430 volts that can power an
EV for a mile or more. I don't know how big the thing is, but a 50aH,
12 volt lead acid battery would be 600 watts for one hour (600wH) and
the 8 farad capacitor at 430 volts is 206 watts for one hour (206wH).
Now, unless I screwed up my math somewhere, it looks like the capacitor
has about 1/3 the capacity of a 50aH lead acid battery. But, the
capacitor is probably several times bigger than the average automobile
battery, so the energy density may only be only 1/10 or 1/20 that of
the battery. What do you think?
[email protected] said:They don't, except in history books.
They energy in capacitors arises from that they
charge/discharge in microseconds.
The energy in lead acid batteries comes
from sponge lead, which is where it's weight comes from.
about 3.1 Wh/kg about 15% of what current lead acid batteries have.
Their costs are over one order of magnitude greater than current Li-ion
cells.
Capacitors for engineered systems are only used for high peak
power and high charge/discharge efficiency. Good applications are
accelerating a garbage truck from zero to ten mph, and back to zero in
the 100 feet between houses.
Very little energy, but lots of power.
For energy storage to give long range they are a nonstarter.
Some say we must tax corporations more. What they do not understand is that
corporations do not pay taxes. One of our governments conditions for their
existence is they collect the taxes from their customers and pass them to
the government.
Bret said:That's on a cost/energy basis?
Regenerative braking EV makes sense on route fleet delivery vehicles
because the range is known or can be managed. There are no surprises.
All trucks wind up at the same garage at night. A mechanic is often
available. It's politically possible to force USPS to adopt new
technology.
Since garbage trucks are expensive anyway they ought to do them first.
Besides, what's most obnoxious about a garbage truck isn't the smell,
but the engine noise.
To have any range, EVs wind up having enough batteries for all the
power they need.
A 70 watt-hr charge/discharge doesn't impact battery life all that much
so a capacitor isn't much of an advantage.
Just do it with the individual income tax.
Bret Cahill
I think you confuse energy and power. The batteries have the energy,
the capacitors provide the power. You need both.
Yes it is, because the little 70 watt-hr capacitor can deliver all it's
energy in a few seconds.
Bret said:The energy density of batteries is too low.
That is because you are 'Bret', the spoiled brat that has no concept of
quads....