alt.autos - 4 new messages in 1 topic - digest

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Today's topics:

* Consumer Reports: GM's Volt 'doesn't really make a lot of sense' - 4
messages, 2 authors
http://groups.google.com/group/alt.autos/t/360dc4f4d62b4736?hl=en

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TOPIC: Consumer Reports: GM's Volt 'doesn't really make a lot of sense'
http://groups.google.com/group/alt.autos/t/360dc4f4d62b4736?hl=en
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== 1 of 4 ==
Date: Thurs, Mar 3 2011 3:45 pm
From: Clive

In message
<01ef9486-40ae-4f31-914d-d6dd56ee619a@l14g2000pre.googlegroups.com>,
dsi1 <david123iwaoka@gmail.com> writes
>passive cooling
New term on me. What is it?
--
Clive

== 2 of 4 ==
Date: Thurs, Mar 3 2011 6:01 pm
From: kludge@panix.com (Scott Dorsey)

Clive <clive@yewbank.demon.co.uk> wrote:
>In message
><01ef9486-40ae-4f31-914d-d6dd56ee619a@l14g2000pre.googlegroups.com>,
>dsi1 <david123iwaoka@gmail.com> writes
>>passive cooling
>New term on me. What is it?

Cooling without active fans or pumps. The Model T used passive water
cooling. Harley-Davidson Panheads use passive air cooling.

The heat issues with the electric car are more due to resistive losses
in the battery than losses in the motor. Active liquid cooling of the
batteries has been suggested. In a lot of cases, though, just having
thermal mass to smooth out the occasional large peak current demands
causing brief peak heat loads turns out to be sufficient.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

== 3 of 4 ==
Date: Thurs, Mar 3 2011 6:24 pm
From: Clive

In message <ikph67$23s$1@panix2.panix.com>, Scott Dorsey
<kludge@panix.com> writes
>The heat issues with the electric car are more due to resistive losses
>in the battery than losses in the motor. Active liquid cooling of the
>batteries has been suggested. In a lot of cases, though, just having
>thermal mass to smooth out the occasional large peak current demands
>causing brief peak heat loads turns out to be sufficient.
This raises an interesting question, if the battery is getting hot
through current draw, then it has greater internal resistance than is
good for it, causing a voltage drop across the motor terminals, which
will of course mean lower torque and top speed.
--
Clive

== 4 of 4 ==
Date: Thurs, Mar 3 2011 7:41 pm
From: kludge@panix.com (Scott Dorsey)

Clive <clive@yewbank.demon.co.uk> wrote:
>This raises an interesting question, if the battery is getting hot
>through current draw, then it has greater internal resistance than is
>good for it, causing a voltage drop across the motor terminals, which
>will of course mean lower torque and top speed.

Right. But what is the question?

Life is just like that. Nothing has zero resistance, and we're talking
an awful lot of watts here. Battery technology improves but there is
always some resistive loss.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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