This guide will take you step by step through how to dismantle the Braun Oral-B Professional Care Type 3728 electric toothbrush and replace the battery. The tutorial is based on the Type 3728 model but may be applicable to similar models such as the Type 4736. The type number of your toothbrush 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 old battery
- Remove circuit board
- Replace battery
- Re-fit circuit board
- Solder in new battery
- Reassemble handle
This is documented in detail below along with lots of pictures. Click on any picture to enlarge it.
We have created a short YouTube video from this guide to Braun Oral-B Type 3728 battery replacement 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 Professional Care toothbrush (Type 3728)
- Original recharging base
- Soldering iron: 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:
To start with, remove any brush heads from the top of the handle and using the screwdriver start to pry off the ring around the shaft. Alternatively you can use pliers with tape inside the jaws to stop them marking the ring.
Put the brush on its charger and gently twist it anti-clockwise to release the catches holding the base of the toothbrush into the handle.
Take the brush off its charger and start to push the shaft in from the top.
Carefully extract the inner workings of the toothbrush without pulling on the thin copper wires.
The first piece to remove from the internal assembly is the power switch plate. This is clipped in on both sides at the top of the brush, see arrows below. Carefully unclip it from one side, then the other.
Time to get your soldering iron warmed up now! Using the soldering iron and desolder pump carefully desolder the battery’s positive terminal solder tag from the circuit board (arrowed below) and bend the metal tag upright and away from the board with a knife so there is no solder left joining the solder tag to the board. Desoldering braid might be useful for this.
Do the same with the two motor terminals (arrowed.)
Carefully unhook the copper wires to the charging coil from under the white plastic clip holding them in place. The clip opens on the right (arrowed below.)
Unclip the white plastic battery carrier from the metal toothbrush frame by sliding the carrier over the metal tabs (arrowed)
Desolder the battery’s negative terminal solder tag from the circuit board (arrowed below) and bend the metal tag upright and away from the board with a knife so there is no solder left joining the solder tag to the board. Take care not to melt the plastic arch which clipped the copper wires in place. You might find it easier to insert the soldering iron head underneath the arch.
Fold the positive terminal solder tag horizontally away from the circuit board (as above) then slide the battery out of its carrier.
Compare the original battery to its replacement. This is a 42mm long by 17mm diameter tagged battery from the shop at ToothbrushBattery.com however, your Type 3728 might be fitted with a narrower 42mm by 14mm diameter battery so check your original battery before ordering!
Using scissors cut both solder tags to the same length as the tags on the original battery.
Very carefully start to narrow down the width of the positive terminal solder tag by first snipping into the tag from the left. Careful not to cut right through! Just go a quarter at a time. Then cut down from the top to remove the piece.
Do the same with the solder tag on the negative terminal, this time cutting in from the right.
Gently unclip the circuit board from its plastic clip (arrowed below) and slide it out of the battery carrier.
Test fit the new battery in the battery carrier to check that the solder tags line up with the channels.
Re-fit the circuit board.
Solder the negative terminal solder tag onto the circuit board.
Refit the battery carrier to the metal frame of the toothbrush then solder the motor terminals and the battery’s positive terminal solder tag back onto the circuit board.
Hook the copper wires for the charging coil back under the hook into the plastic arch (arrowed below).
Clip the power switch plate back into the metal frame of the toothbrush making sure the pins locate correctly on both sides.
Gently push the innards of the brush back inside the outer handle.
Put the toothbrush back on its charger and, while pushing down vertically on the brush to close the base, twist the handle clockwise to engage the latches.
Fit the ring back around the shaft making sure it is firmly pressed into place. An a 10mm or 11mm ring spanner or similar might be useful for this.
You should now have a fully reassembled Professional Care toothbrush! Put the brush on to charge for a full 24 hours and check that the charging light starts to flash. Please recycle your old battery either at a local civic amenity or a supermarket collection point.
Please leave any questions or comments about this guide on our dedicated blog post here.