Path: utzoo!attcan!uunet!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: 9-volt / rocket launcher?
Summary: High energy batteries...
Message-ID: <2865@kitty.UUCP>
Date: 28 Dec 88 03:00:04 GMT
References: <2557@ddsw1.MCS.COM> <680@eplunix.UUCP> <17942@glacier.STANFORD.EDU>
Organization: Recognition Research Corp., Clarence, NY
Lines: 50

In article <17942@glacier.STANFORD.EDU>, jbn@glacier.STANFORD.EDU (John B. Nagle) writes:
>       The highest power-to-weight ratio in batteries is found in the Polaroid
> PolaPulse (TM) battery.

	As far as I know, in a _commercially_ available battery, the highest
energy-to-weight ratio is found in a lithium-thionyl chloride cell.  Short
circuit currents for a D-cell sized lithium-thionyl chloride battery can
approach HUNDREDS of amperes.  As a demonstration, I have seen a string
of such batteries having a total size less than 2 D-cells start a full-sized
automobile.  Lithium-thionyl chloride batteries are not the same as the
lithium batteries used in watches and electronic memory circuits (this
variety is typically a lithium-manganese dioxide cell).  Electrochem
Industries in Clarence, NY is a major manufacturer of lithium-thionyl
chloride batteries for commercial and military applications.

> This is a flat object about the size of a playing 
> card and about 2mm thick.  One is inside every Polaroid film pack.  These 
> units are designed to deliver about 10-20 amps, as I recall, for a second
> or so at a time, and provide energy to drive the motor that forces the film 
> through the developing rollers.  You can buy the batteries from Polaroid in
> a somewhat more convenient form than one obtains by dismantling a film
> cartridge, and Polaroid sells a developer's kit for these units.

	Polaroid has been discouraging OEM sales of the Polapulse battery,
and now sells it indirectly through an exclusive marketing agreement with
Power Card Corp. in Waltham, MA.

	Interesting enough, the Polapulse battery uses pretty conventional
Leclanche chemistry (zinc and manganese dioxide); the physical design of the
battery is indeed clever, though.  The Polapulse P100 (the original SX70
battery) has some interesting discharge characteristics.  Instantaneous
short circuit current is 19 amps, which drops to 8.5 amps after 30 seconds,
and which further drops to 4 amps after 60 seconds.  At a continuous
discharge current of 0.1 amps the P100 is rated at 0.232 ampere-hours,
but at a continuous discharge current of 5.0 amps, the rating is only 0.018
ampere-hours.  High discharge currents have an extremely deleterious
effect upon the energy life of the battery.

	Gould makes a flat lithium-manganese dioxide battery under the
tradename of Powerdex, which is roughly comparable to the Polapulse.
The Gould battery has much higher energy capacity (1.4 ampere-hour),
but cannot provide discharge currents in excess of 0.5 ampere.  As I
understand it, Gould is actively pursuing OEM applications for their
battery; Polaroid doesn't seem too interested unless you want to buy
100,000,000 batteries per year. :-)

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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