Date: Wed, 07 Jul 1999 15:48:36 -0400 (EDT)
From: Marty Goodman MD KC6YKC <MARTYGOODMAN@delphi.com>
Subject: Eveready 1.5 V LiFeS vs 3.0 V LiSO2 cells
Message-id: <01JDAE4XL8XO8XIYE4@delphi.com>

 
Vic Garza wrote:
 
"What about the wasted energy associated with these AA lithiums
which have somehow had their voltage reduced from
the normal 3V down to 1.5V?"
 
 
Unfortunately, Victor is mistaken in many respects in writing the above.
 
First, THE NORMAL VOLTAGE for those Everready batteries IS roughly
1.5 volts.  Cell voltage is a natural function of the chemistry
of the cell.  It derives from the difference in the electronegativity
of the elements used for the poles of the cell, to oversimplify just
a bit.   And the natural voltage for a LiFeS chemistry cell is roughly
1.5 volts.  The voltage on those cells is NOT, as Victor mistakenly
alleges, "somehow reduced" in any way.
 
More important, tho, is the fact that Victor is wrong in the most
important aspect of his assumption in the quoted sentence:  He
implies that the Eveready LiFeS cells somehow aren't as energy efficient
as the 3 volt LiSO2 cells.   But the fact is that in terms of the units
that are meaningful for us, watt hours per gram, Eveready LiFeS cells
offer about 90% or more of the energy efficiency of the LiSO2 3.0 volt
SAFT D cells.   SAFT LiSO2 cells are not widely and or easily
available.  Eveready LiFeS cells are available at most Home Depot and
all Radio Shack stores.  The Eveready cells are legal for
transport on commercial aircraft, where the SAFT cells are NOT. Given
this, the very small degree to which the Eveready LiFeS cells are not
quite as energy-dense as the SAFT cells are (10% or so difference) is,
for most purposes, not a significant matter.  And, in most applications,
vastly outweighed by the wide and easy availability of the LiFeS cells.
 
   Victor also compares the LiFeS cells to the 3 volt photo batteries.
I've done the same, and found the LiFeS to be more cost effective, and
more widely available.  As far as power per unit weight, they're very
similar.  And as far as easy of use, they are nearly identical, in that
the AA LiFeS from Eveready has roughly similar overall power to the 3V
1/3 A or whatever its size is photo battery.
 
   ---marty