6 AA cell 3V battery cartridge conversion instructions

Use 6 AA NiMh cells in place of 2 D NiMh cells for faster recharge times.
This is the 6AA battery holder. While it
comes set up with the cells wired in series
for 9V operation, this modification will turn it
into a 3V battery cartridge that can be used
directly in place of 2 D cells.
There is a black wire that runs from one end of the holder to the
other. Locate and cut this wire at both ends and remove.

Note that at one end of the holder there are two springs, and one
spring at the other end. To change this over to 3V operation, the
first step is to move the single spring to the same end of the
holder as the other two springs.
Lift and cut the spring loose leaving as long a piece of wire
attached to the spring as possible. Form the tail piece of wire
so that it points down from the center of the bottom side of the
spring.
Mount the spring in the end of the holder with the other two
springs were there is no spring.

It is useful here to use a dead AA cell to hold the spring in
position during soldering. Do not allow the cell to compress the
spring any, just hold it in position.
Solder the spring wire into the rivet.

Work quickly using the minimum amount of heat possible.
Monitor the plastic around the rivet. If it gets too soft, stop and let
things cool before doing any more soldering. It is also helpful to
blow on the solder joint after the solder flows to quickly cool it  
down and allow the plastic to re-harden.  
Note that one rivet is missing at this end.

It's not actually missing, just covered up with a thin black plastic
round disk.

Pry the cover disk off with a knife point and discard.  
Solder a 5 inch length of bare wire to a washer slightly larger
than a U.S. Penny.

Brass washers work great for this application
Bend and form the wire so it connects all the rivets together at
this end.

Solder the wire to all the rivets.
After things cool back down, pot the washer onto the holder
using epoxy glue.

Allow it to harden before continuing.
Note that there is a rivet missing on the other end of the holder.

It really is missing this time!
Drill a 1/16 inch hole where the missing rivet should be located.
Form one end of a 5 inch piece of wire in a small spiral. Form a
solder bead on the spiral of wire.

This will be used as a + battery contact.
Insert the solder bead and wire so the wire points out the end of
the holder.

Epoxy can be added around the base of the solder contact to
hold it in place.
Form the wire so it connects to the two rivets.
Solder the wire to the rivets and terminating in a solder joint on a
contact card.  Add lots of solder to build up a nice dome shape for
the positive contact.
Epoxy the contact board in the center of the holder end. Allow the
epoxy to set up before proceeding.  

Verify proper operation of all three cell banks by testing each position
with 2AA cells installed.

That's it, the 6AA to 2D battery cartridge is now ready for use...