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Batteries {Was: Re: Hacking Wolfram|Alpha)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg102262] Batteries {Was: Re: Hacking Wolfram|Alpha)
  • From: AES <siegman at stanford.edu>
  • Date: Mon, 3 Aug 2009 05:46:35 -0400 (EDT)
  • Organization: Stanford University
  • References: <h494vp$q0g$1@smc.vnet.net> <h4p6ai$l6r$1@smc.vnet.net> <h53o3c$1k4$1@smc.vnet.net>

In article <h53o3c$1k4$1 at smc.vnet.net>,
 "gigabitbucket at BrockEng.com" <gigabitbucket at BrockEng.com> wrote:

> Looking for the energy stored in a 18v, 3.0 amp-hour lithium ion
> battery, I fed
> 
> "3.0 amp hour 18 volt in Joule"
> 
> into W|A's query line and get back a page at
> , which reports the answer as 194 400 J. This matches the answer
> returned by Units`.
> 
> Cheers,
> Fred Klingener

If you're interested in batteries (they're more useful overall than 
W|A?), you might try asking W|A something like

  "3.0 amp hour 18 volt ?? pounds in feet"

(with suitable rearrangement or rephrasing).

That is, the energy delivery capabilities of any battery technology can 
be expressed by a single number:  the "battery height" of that 
technology, defined as the maximum height to which any battery using 
that technology can potentially lift itself against gravity, using some 
kind of perfectly efficient lifting machinery.

I've not done a systematic exploration of the battery heights of 
different battery technologies (lithium, lead acid, etc), but this is 
quite a useful as well as instructive number.  If the battery height of 
the battery technology used in your Prius or Tesla is 10,000 feet and 
the batteries make up 10% of the weight of the vehicle, it doesn't 
matter what the claimed range of your vehicle may be -- you're never 
going to get from A to B, even starting out fully charged, if there's a 
1,001 foot pass between A and B.


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