This guide will take you step by step through how to open and dismantle the Braun Oral-B Professional Care Type 4729 electric toothbrush then repair it by replacing the internal rechargeable battery. The guide may also be applicable to similar models including the Type 3746. The type number of your brush is marked on the bottom of the handle.
For other toothbrush models and type numbers the battery replacement procedure is slightly different so please see our other guides to toothbrush battery replacement instead.
The basic method is:
- Dismantle handle
- De-solder circuit board and old battery
- Solder in new battery (2 sizes available)
- Reassemble handle
This is documented in detail below along with lots of photos. Click on any photo to enlarge it.
We have also created a short video from this guide to Braun Oral-B Type 4729 battery replacement on our YouTube channel, which you can also watch below.
Any damage to yourself, your toothbrush or anything else is entirely your responsibility. This guide is for professional, educational purposes only and is offered without guarantee or liability.
Tools / Parts / Equipment
- Braun Oral-B Triumph Professional Care Type 4729 toothbrush
- Original recharging base
- Soldering iron: Fine tip, electronics grade (about 18-25 watt)
- Solder: Lead-free silver solder is great for this
- Solder sucker (also known as a desoldering pump) and/or desoldering braid/wick
- Craft knife e.g. scalpel, snap-off, retractable or Stanley type
- Small flat-bladed screwdriver: 2 to 4mm wide
- Replacement battery with solder tags. Either:
Using the screwdriver or pliers with tape over the jaws carefully pry off and remove the ring around the shaft of the toothbrush.
Place the toothbrush on its charging stand and carefully twist the handle anti-clockwise to release the latches holding the base into the handle. It will spring open slightly.
Push the shaft of the toothbrush into the handle so that the internal mechanism starts to slide out of the handle casing.
Remove the inner workings from the handle casing.
Using the screwdriver gently press the two clips (arrowed below) on one side of the switch cover plate, then the other side, to release the plate and remove it.
Gently unhook the copper wires connecting the charging coil to the circuit board from the plastic arch (arrowed below) and move the base to the side for access.
Time to get your soldering iron warmed up now! Using a desoldering pump or braid desolder the two motor connection tags (arrowed below) from the circuit board and use the knife to bend them upright.
Unclip the plastic battery carrier from the metal clips (arrowed below) on the frame of the toothbrush mechanism and slide the carrier off the frame.
Desolder the positive battery terminal (arrowed below) from the circuit board and bend it upright.
Desolder the negative battery terminal (arrowed below) by inserting your soldering iron horizontally under the plastic arch. While the solder is still molten push the battery in from the positive end so it starts to slide out of the plastic carrier.
Slide the battery right out of its carrier and measure its length and diameter. This one is 42mm long and 14mm diameter but different versions of the Type 4729 have different size batteries depending on the features of the toothbrush. You might also like to modify your toothbrush by cutting down the spring so you can fit a longer, higher capacity battery.
Unclip the circuit board from the plastic battery carrier, starting with the side clips (arrowed below.)
Compare the original battery to its replacement. Please support us with writing these repair guides by buying your replacement battery through the links to our online shop shown. In the version of the Type 4729 toothbrush shown it was a 42mm x 14mm battery. However, yours might be fitted with a 42mm x 17mm battery so measure your original battery before ordering.
Using scissors trim the solder tags of the new battery to the same length as those on the original battery.
Shape the tag on the negative terminal by carefully cutting in from the side using the tip of the scissors. Then cut down from the top.
Do the same with the tag on the positive terminal.
Fit the battery into its plastic carrier.
Clip the circuit board back into place, making sure that the battery’s solder tags line up with the solder pads on the board.
Bend the positive tag over and solder it to the circuit board.
Slide the battery carrier back on to the metal frame of the toothbrush, ensuring it clips into place.
Solder the two motor connection terminals back on to the circuit board.
Bend the battery’s negative tag over and solder it to the circuit board.
Carefully hook the copper wires back under their clip on the plastic arch. Check that they are all still intact and connected as damage to these wires is a common cause of charging problems.
Clip the button plate back on to the toothbrush frame.
Slide the workings of the toothbrush back inside the outer casing and push the base in as far as it will go.
Put the toothbrush back on its charger and push down on the handle to compress the spring inside the base. Turn the handle clockwise to engage the latches in the base.
Plug the charger into a power socket and check that the green light starts to flash. If it doesn’t flash then check your soldering for dry joints and short circuits. The brush might need 10 seconds on charge to reset the internal electronics so that it recognises the new battery and will then allow you to pick up the toothbrush and switch it on.
Re-fit the ring around the shaft, making sure that it is firmly pressed into place. An 11mm ring-spanner might be helpful for this.
You should now have a fully reassembled Braun Oral-B toothbrush! Put the brush on to charge for a full 24 hours before use. Please recycle your old battery either at a local civic amenity or a supermarket collection point.
Please leave any questions, tips or comments about this guide below.