OB300-530 battery rebuild procedure.

I start with a wide, rounded-edge flat-blade screw driver,
specifically the one that is in my Victorinox Champ Swiss
Army Knife.  I carefully work it between the plastic case
seams and slowly work around the edges until I have
completely broken the ultrasonic weld.

	After I have done that, I carefully cut out the
old batteries, close to the cells.  I leave the metal
strips (tabs) coming from the case connectors as long as
possible.  Make note of cell polarities and use a Sharpie
or other permanent marker to mark the plus-ends of the
cells in the bottom-half of the battery case for future
reference.

	There is a diode, a high-temp thermal fuse, a
low-temp resetting thermal cutout (rectangular device
with leads coming out of one end, one of them connected
to the high-temp thermal fuse) and a current limiting
resistor in series with the cells.  Leave the diode
between case connectors intact.  You will not be able to
salvage the high-temp thermal fuse (shaped like a tiny
bullet with leads out both ends) unless you use a hemostat
heat-shunting clamp when re-soldering.  I usually discard
the high-temp thermal fuse and the current limiting
resistor (small, flat, white thing between the left cells,
when bottom-case half contacts facing up and top the
right).

	I use NiMH cells from DigiKey with solder tabs.
The tabs make assembly MUCH easier.  Soldering directly on
the cells is both dangerous and difficult.  Manufacturers
and volume-rebuilders use a miniature spark-welder.
Unless you are rich, you will want to use a quality
soldering iron with a fine tip.

www.digikey.com
Catalog page 518.  
Part #P016T-ND $4.93ea. $44.33/pack of 10

	I start with the two left cells first (bottom-case
half contacts facing up and to the right).  Once I get the
cells in place, noting polarity, I carefully fold the
solder tab strips to allow them to extend from the left
half of the battery case to the right half in the little
grooves that were used by the old batteries.  Using Scotch
tape to temporarily maintain this rotational alignment, I
then remove the cells from the bottom and fold the far-left
tabs so they overlap.  I now solder the tabs together and
put the cells back into the lower-half of the battery case.
 Always be careful not to melt the plastic skin on the
battery and short it out at the top.

	Now I work on the right side.  I place the two
cells (note polarity again) in the case and rotate them so
I can get the solder tabs lined up.  Starting with the
lower-right cell, I take its left tab and fold it to meet
the right tab from the lower-left cell.  I now note the
rotational alignment of the cell and remove the cell and
fold his right tab to interconnect with the tab coming from
the appropriate case connector.  I clip the excess left-tab
with my Army Knife scissors and then solder the bottom cell
tabs together.  Don't solder the right-tab just yet, you
need to save that for last.

	This leaves the last cell, the one closest to the
case connectors, in the upper right corner of the
lower-half of the case.  Noting polarity, I fold its
left-tab almost-flush to the cell and orient the low-temp
resetting thermal cutout (rectangular thingie) so I can
solder it between the tabs of the two top cells.  I cut off
the high-temp fuse, keeping as much length on the tab
coming out of the thermal cutout as possible.  The left
cell tab will be in the valley between the two right cells.
Noting the rotational alignment of the cell, carefully fold
the right-tab up at an angle to properly intersect the
appropriate case connector.  Make sure that the tabs folded
over the center of the case are flush and in their grooves.

	If everything has gone well, you can now solder the
upper-right cell's right tab to the case connector.  Use
Scotch tape as a layer of insulation over the connection
after the solder has cooled.  Now you can connect the right
tab of the lower-right cell to its case connector and
solder it.

	If you have been careful and kept all connections
tight and short, you will be able to put the top case half
back in place and press the case together with finger
pressure.  If the seam meets closely all around, you may
safely glue the case together or tape it together with
Scotch tape.  I tape mine so I can get back into them
easily in the future.  Looks are not a high priority for
me.  If the case does not close all of the way, open it
back up and figure out what is getting in the way.

That's it!