New Batteries for a Braun Shaver

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.

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.

Comments

[nbevan]

I successfully replaced my battery with a 1200 mAh NI-MH battery with tags, that I ordered online.  I left the old tags protruding from the circuit board, and cut the new tags to length.  The razor now holds charge as new.

Elsewhere I found instructions for a better way of opening the razor: undo the screws at the top, then pull it apart until you can use a long screwdriver to move the plastic lug (held by a spring) visible at the bottom sideways.  The lug has a catch on it that holds it in position for reassembly.

[Phil B]

I wonder if our shavers may have been constructed differently. 

[nbevan]

Sorry: you are right.  

The picture looks the same, but mine is a 2450.  I am guessing that the technique I used will not work for the 5510?

[xevious]

What NiMh AA flat top batteries did you use with your shaver?  There are a number of models available with different mAh ratings.  I'm just curious if that makes a difference to the shaver firmware, as the higher the mAh rating the longer the charge.  Braun probably did not use the highest mAh rated batteries as OEM, to save on cost.  I'm wondering if 2200mAh cells (2.4v combined) would be a good replacement.  What do you think?

[Phil B]

 I had a couple of new NiCad AA cells in my possession and used them.  I think the 2200 mAh cells you mentioned would work.  I did not see any chipsets inside my shaver (1990 vintage), which would be necessary for any firmware.  

It was immediately after doing this project that I went to replace the NiCad cells and learned they were no longer in stores available to me (Radio Shack, Batteries Plus).  The folks at Batteries Plus suggested simply using NiMH cells as substitutes for NiCad cells.  That surprised me, based on what I had read up to the present.  I have not tried it yet, though.  

Thanks for your comment. 

[xevious]

Interesting.  Yeah sorry, when I said "firmware", I had a later model in mind.  The 6000 series on up has firmware to regulate various things, and to run the LCD when present.

I just learned that someone used a set of 1650 mAh NiMH 1.2v batteries in their shaver and they worked out fine.  I'm going to go with the 2200 mAh ones; it'll be interesting if the shaving time is extended between charges over OEM performance.  Maybe I'll do a writeup of replacing the cells in the 7000 series.  :-)

[Phil B]

 I wish you well with your project.  I would be interested if the process for opening the case and removing any poison pills that might prevent battery replacement by the owner has changed.  I hope something in my Instructable will be useful to you.  

[xevious]

Well, my attempt failed.  I detached the old cells from their tabs, installed the new ones, soldered the tabs to the cells, did a circuit check to be sure the contact is good, reassembled the shaver, then tested it out.  The shaver actually worked, but the battery level was low--clearly they needed to be charged.

So, I plugged in the shaver and let it go through a charging cycle (60 minutes).  When the flashing light went off, I disengaged the shaver from the cord, then tried to operate it.  DEAD.  I plugged it back in and tried to run the shaver, and it did work.  It just won't run off the cells.  I double checked the circuit again and it showed OK--the batteries are fully charged.  I suspect that something must have gone wrong on the circuit board.  The only thing I can think of is that it isn't designed to handle a 1.2v battery that has a 2300mAh rating.  I quite sure I didn't introduce any issues directly (e.g. short or broken circuit).

[xevious]

Good news!  I determined that my soldered connections were faulty.  I didn't have proper solder for the job (too small a wire and too quickly curing flux) and my extreme caution against heating up the batteries caused poor soldered connections.  So, I used adhesive backed aluminum tape to secure the leads this time.  It works!  The higher mAh rating seems to be confusing the firmware, as the low battery light is flashing on the shaver, but it's running very strong.  It'll be interesting to see how much run time I get on a full charge.

[Phil B]

 I am glad to hear you found the problem.  I have heard of poor solder joints acting like a diode.  I would not have expected quite the problems you had.  I did not worry too much about overheating the batteries.  Roughing the battery ends up with sandpaper and tinning them before soldering the wires to the battery ends worked very well. 

[xevious]

Thanks.  I hadn't heard of any "poison pills" before seeing your posting. Braun must have done away with those on later models, as I opened up my 7526 and 8595 shavers, disassembled, cleaned whisker debris out of the casing, then reassembled with success--both shavers still work.  I've got a spare shaver (model 7526) that has well worn batteries, which will be the tester for this battery replacement.  If it works well, I'm going to replace the cells in my other Braun shavers.  Higher mAh rating means longer life.  The new cells I'll be putting in are rated at 2300mAh (still 1.2V) and can take up to 1000 cycles (versus the usual 500 on the generic NiMH AA cells).

[pmiller10]

xevious, Are you still around? I found this thread and see that you saw you successfully opened your 7526... how?
It doesn't match the description/picture above. The charger plug isn't round so doesn't turn/unscrew.

[YvesM]

Pmiller10 - just thought I'd share - I just replaced the batteries on my 7526 (almost bought a new one before deciding to try the battery replacement) - am I glad I did - I bought new 1650mAh from www.batteriesamerica.com for about $13 including shipping, soldered them in and voila, a like new shaver - LOVE IT! Before the batteries did not hold a charge anymore and I had ot use it plugged in, but now it is like a speed racer. I read elsewhere the original batteries were 1100 mAh on the 7526, but the max. people have had success with was 1650mAh, so that is what I went with. Be sure to get the batteries with Soldertabs attached - much easier. Good Luck!

[xevious]

Hello pmiller,
Yes, the 7526 is a different model; this instructable is based on a 6000 series shaver. The bottom socket surround is rectangular, with a protrusion in the center where you insert the cord. To remove the surround, or "plug", you insert a small screwdriver just within the lip of it (so you are getting leverage on the plastic). You then apply pressure to pry the surround off. There are 4 little hooks that hold the surround on, pointing to the front and back panels of the shaver. So you want to pry in that direction for easier removal. Good luck!

[xevious]

I neglected to follow up with results here... just thought I should make a note, for posterity.

My attempt to use 2200mAh and higher batteries failed miserably. The additional storage capability of the batteries seems to confuse the shaver firmware. As I had suspected might be the case, it is tuned to deal with a specific battery capacity. So, it's important to use batteries that are as close to the originals as possible. I believe the originals were more like 1400mAh or 1500mAh. 1650mAh is probably on the edge of tolerance for the shaver, and it probably doesn't give much more shaving time than a 1500mAh battery. I'd say it's best to stick as close to the original specs as possible.

[Phil B]

I am sorry it did not work for you. Will you try again with different batteries?

[xevious]

That's my intent. I located a set of 1500mAh and 1800mAh cells that weren't very expensive, but seem to be of similar construction to the original batteries (plain mono colored vinyl sheath around the cells, generic printing on the sides indicating model/mAh). I've had other projects that have taken priority, and I picked up another used shaver on the cheap with batteries still working well. So, it'll be easier to do the battery swap, as any failure won't leave me without a working shaver. :-)

[canida]

Nice. Defeating those "poison pill" mechanisms designed to prevent equipment from being user-serviceable is so rewarding, isn't it?

[Phil B]

Thank you for the comment. I think this is the first poison pill device I have encountered after a lot of years of working on all kinds of stuff.