From: ka1gt@cbnewsm.cb.att.com (robert.m.atkins)
Subject: Rechargable 2CR5s. Quest for the holy grail?
Organization: AT&T
Date: Fri, 28 Aug 1992 17:42:18 GMT

WARNING!WARNING!WARNING!WARNING!WARNING!WARNING!WARNING!WARNING!WARNING!WARNING
(especially for US residents with lawyers)
The following information on 2CR5 recharging is for scientific interest. If
you try any experiments based on the data presented here and injure yourself
or your camera it's your own fault. Do not try this at home. We need another
Timmy......

Lots of people hate the rate at which cameras comsume expensive 2CR5 lithium
cells. Unfortunately there is no available rechargable 2CR5 substitute availble
at this time. However...

1 - It is possible (but NOT recommended) to "recharge" or "rejuvenate" a 
standard primary lithum cell using a VERY low recharge current. The cell will
not gain back 100% of its initial power, but may reach 25-50%. This process
can be dangerous because of the possibility of internal shorting either
during recharging or during discharge. To put it clearer it may blow up while
you are trying to rechage it, or it may blow up in your camera. On the other
hand it may not. If it does you could be in real trouble, since lithium is
not the nicest metal to have blown around (not to mention the electrolyte),
so you have the potential for fire and/or corrosive products to be scattered
around. If you had the last 2CR5 on the planet, it might be worth experimenting
with this, however the sane among us would be well advised to go out and
purchase a new 2CR5 at around $10(US) rather than risk life, limb and camera.

2 - I have constructed a 2CR5 form factor rechargable NiCad cell pack using
four (4) 1/3AA cells. For a 6v battery you would need 5, but there are no
available NiCads that can be assembled into a 2CR5 form factor using 5 cells.
The 4 cell pack has a nominal 4.8v rating, though at full charge it may reach
over 5v. This cell will power my EOS10s through about 1 roll (36) of film if
I don't do much other than press the shutter button 36 times. If I do a lot
of "prefocussing" and the like it will not make it through 36 frames. Note that
the discharge characteristics of a NiCad pack will be different from that of
a Li cell. It is possible that the use of a NiCad pack could cause camera
malfunctions - in which case the manufactureres warranty would probably no
longer cover you. Note I didn't even think of trying to use flash with this
battery, not only would it drain it REAL fast but it might even cause other
problems. This 2CR5 alternative is much preferred to method 1. It is not
likely to damage you, but could damage your camera.

3 - It is easy to construct a 6v battery pack using AA's, NiCads, Gel-cells
or whatever and connect it to the camera via a 2CR5 shaped adapter. You can
carve one out of wood, or use a dead 2CR5 upside down, and attach electrical
contacts in the right place. This system works great, but having a cord from
the camera to the battery pack restricts mobility a lot. It may be worth doing
for very low temperature or studio work, but is not much fun in the field.
Note of course that using ANYTHING but the 2CR5 cells will probably invalidate
the camera manufacturers warranty should a problem occur.

Note that since I am in the USA (land of the free and home of innumerable
lawyers) I would point out again the possibilities of damage to yourself
and your equipment that might result from trying to actually use any of the
information presented here.

Bob Atkins