This is my Braun 5510 shaver with rechargeable batteries. The batteries no longer hold a charge. It is possible to use the shaver with the AC cord normally used for charging. I wanted to replace the NiCad AA batteries with new cells.
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Step 1: Opening the Case
The first problem is how to open the case of the shaver. This graphic from the shaver's manual gives some description. But, these instructions assume you will no longer use the shaver after opening to remove the old batteries for recycling. The seal is green as shown. Use a larger coin to push and break the seal. Then rotate the round fitting where the cord attaches counterclockwise about 45 degrees. Rotating this cord jack fitting required considerable force. I had to grasp a US quarter dollar with a pair of pliers to apply enough force.
Step 2: More on Opening the Case
In MS Paint I added some colored lines to illustrate the steps in opening the case. As described in the previous step, rotate the fitting around the charging cord jack counterclockwise (red arrow). There is an end cap on the case as shown by the yellow lines. When the fitting around the cord jack has been rotated, the end cap slides off (yellow arrows). Then the major portion of the case slides away from the innner workings of the shaver (green arrows).
The inner carcase of the shaver is not shown here, but it is a clamshell. Pry it open only as far as needed at the end of the shaver shown in the photo. Slide the inner case for the circuit board and motor out of the shaver.
Step 3: Inner Case Catches
The inner case around the circuit board is an upper piece of translucent plastic. The lower piece is black plastic. Four snaps hold the two pieces together. Gently pry each off of its hook. The graphic illustrates the hook catches.
Step 4: The Cells
The photo shows one of the original cells. Metal tabs spot welded to the ends of the cells protrude through slots in the circuit board and are soldered in place. I marked the circuit board with "+" and "-" so I would not forget the polarity. It is easy to become confused.
My new cells did not have metal tabs spot welded to them. I decided to use some bare stranded wire. I pushed it through the slots in the circuit board and soldered an end to the circuit board. Then I cut it to length to reach the point of contact on the cell ends. I roughed up the ends of the cells with sandpaper and tinned them with solder. I soldered the cells to the wire pieces.
Put the circuit board back into its case and slide its case into the shaver.
Step 5: Assembly
Braun builds a poison pill into its shavers so you cannot assemble the shaver after replacing the batteries. Working around that poison pill is the second important thing in this Instructable, after how to get the case open.
Not recommended is what I did. You can see that I tried chewing up the cord jack fitting with a Dremel tool and cutter bit. It is not necessary and does not work, anyway.
Step 6: The Poison Pill
Braun uses two metal pins like the one shown below to fall into place and lock the cord jack fitting so it cannot be rotated clockwise back to its original position after the seal has been broken and the shaver has been opened. This pin is shown vastly enlarged. The actual pins are only about one quarter inch in length in all. As long as the cord jack fitting cannot be rotated back to its orginal position, the charging cord cannot be used with the shaver. These pins need to be removed, but they are hidden from view.
Step 7: Removing the Locking Pins
In the graphic you will recognize the cord jack fitting (black face with grey contrasting color to highlight the three dimensional aspect of the graphic). The two pins are inside the cord jack fitting where you see the red dots.
When the shaver case is open you will see a plastic piece shown here as tan. It is actually grey, but I wanted its color to contrast with the rest of the graphic. The pointed ends are inside pockets made of translucent plastic. With a drill bit or a jeweler's screwdriver push the pointed ends toward each other to release the piece. Then slide it away from the assembly (arrows with feathered back ends). The cord jack fitting can now be lifted out very easily. The locking pins will likely fall out while you are removing the cord jack fitting. Discard them.
Reinstall the cord jack fitting and its retainer. You can now rotate the cord jack fitting in either direction as needed.
Step 8: Assemble the Shaver and Charge
I could not get the cord jack fitting to engage so that it also locked the parts of the case to keep the case from sliding and opening when I applied pressure to the shaver's sliding switch. It should work, but it did not for me. So, I drilled a hole in the side of the shaver and inserted a short screw to keep the parts from sliding away from each other. My screwhole came to be larger than I wanted it to be, so I filled the hole with hot glue and pushed the screw into the hot glue. It looks ugly, but it works.
Step 9: Attaching the End Cap Again
The end cap also did not want to stay in place, since I could not get the cord jack fitting to lock the parts of the case. So, I ran a small bead of hot glue on the front and back of the shaver and pushed the end cap into place. You can see a little of the hot glue bead in the seam above the word "Braun."
Other than looking a little worse for the wear, my old shaver now works very well with its new batteries.