About seven years ago I bought a Braun Cruzer3 shaver and now, finally, its rechargeable battery started giving up. However, I still had fresh grille and razors and it was a shame to replace an otherwise perfectly-functioning device. So I decided to try to replace the batteries. Here are the steps I took to do it. There are probably not many people in the world still using these, but perhaps it will help with newer models as well.

DISCLAIMER: I’m in no way responsible for any damage caused to the shaver, yourself, your cat, or your house, as a result of following my instructions. This will also void the device’s warranty. Proceed at your own risk!

To complete this you’ll need:

  • A Torx T8 screwdriver. A flat-blade screwdriver of a certain size could possibly do as well.
  • A small piece of flat copper or brass, about half-millimeter thick.
  • A soldering iron and soldering wire.
  • Replacement batteries. They must be AAA size, NiMh type. I used Varta, bought in a general store. The capacity shouldn’t matter, as usual the bigger the better.

Here’s the nervous patient, right before the operation. Before

Remove the screw at the bottom, beside the charger connector. Bottom screw in

Here it is. Bottom screw out

Pull the bottom, rubbery cover off. Firmly, but gently. It takes an effort. A hold as shown on the picture seems to work well. As you do this, a couple of security tabs break-off somewhere inside, and afterwards the cover slides on and off easily. Apparently this is how the service would be able to tell whether you opened the shaver or not. We won’t care about that by now. As to the cover, the screw will hold it OK. Pulling the cover

It slides off like this. Cover slid

And here it’s completely off. You’ll see plenty of hair inside at this moment, if you used the shaver for a considerable time. I cleaned them off before taking the picture, to spare you the view. Cover off

Next remove the screws on the sides of the control board housing. Left housing screw Right housing screw

Here the housing is off. You can see the contacts for the on/off button, the LED, and the motor, and the rubber seal around them. Pretty neat! Housing off

You can use a flat screwdriver to help slide the control board out of its housing, as shown. Pulling control board

Here is the control board, out of its housing. Control board out

The factory batteries are sitting pretty tight in there (you’ll see why next). Use a flat screwdriver, or something similar, to get them out. Pulling first battery Pulling second battery

The battery terminals have little round pins welded onto them, which apparently help hold the batteries firmly against the board’s terminals in the presence of motor’s vibration. Battery negative terminal Battery positive terminal

Here are four of the board’s battery terminals. You can see little round indentations where the pins are supposed to rest. Control board terminals front Control board terminals back

Since we are not likely to get anything like these batteries with pins easily, we’ll have to do without them. The standard AAA batteries fall out of the holder easily, and are not likely to have good contact as is. So, I had the idea to make them fit tighter by soldering a piece of copper to each of the control board’s negative terminals. Don’t solder anything to the batteries themselves - you can easily ruin them with heat from the soldering iron!

Here’s a piece of a salvaged copper stock I used. Copper stock

I cut little squares and bent them in the middle slightly in an attempt to get a more reliable contact. Copper contacts

Here they are soldered in. Soldered contact back Soldered contact front

If you look inside the holder, you should be able to see the polarity marks at the bottom. Here the plus is visible, and you can just about see the minus. I chose to solder the copper to the negative terminals, presuming that there will be more area to make contact with and it will be more reliable.

Observe polarity when inserting the batteries! Soldered contacts both plus polarity marks

Aaand the new batteries are in. New batteries in

Slide the control board back in. Make sure it goes in straight and easy, don’t force it. Don’t make the mistake shown on the photo! Skewed control board

I put a piece of electrical tape on top of the batteries (visible through the housing) to give them a tighter fit and prevent them from rattling from motor vibration.

Now the board and the housing are ready to be put back. Control board inside

The housing is back on. Housing in

And the rubbery cover as well. Cover on

You probably bought your batteries pre-charged, and by now tried turning the shaver on and it didn’t work. Don’t be alarmed, this is normal. Just plug the powered charger in for a moment, disconnect, and try again. It should work! This is likely to not allow the shaver to be turned on with low charge (no batteries = low charge), so the batteries wouldn’t discharge too much and leak.

After the replacement, I’ve used the shaver for two (now rather long) recharge cycles, and saw no problems.

Good luck with your repair!