This guide will take you step by step through how to open and dismantle the Braun Oral-B Sonic Complete electric toothbrush and then repair it by replacing the internal rechargeable battery. The tutorial is based on the Type 4717 Sonic Complete model which is available in either 2-mode or 3-mode variants and in both blue and white. 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:
- Open and dismantle handle
- De-solder old battery
- Solder in new battery
- 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 Sonic Complete 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 use only and is offered without guarantee or liability.
Tools / Parts / Equipment
- Braun Oral-B Sonic Complete toothbrush
- 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 56mm x 17mm 2.4V NiMH battery available here from ToothbrushBattery.com
To start with, remove any brush heads from the top of the handle.
Put the handle on its charger and, while holding the charger steady, start to twist the handle anti-clockwise a quarter of a turn until the latches holding the base cap in release and the toothbrush springs upwards slightly.
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 from the charging coil.
Carefully unhook the copper wires to the charging coil from under the black plastic clip holding them in place. The clip is open on one side (arrowed below.)
Time to get your soldering iron warmed up now! Using the soldering iron and desoldering pump carefully desolder the battery’s positive terminal solder tag from the circuit board (arrowed below) and bend the metal tag upright with a knife so there is no solder left joining the solder tag to the board. Desoldering braid might also be useful for this.
Turn the toothbrush over so the battery is uppermost.
Using the screwdriver, pry out the battery at the positive end and gently bend it up and over so it pivots where the negative tag is attached.
Using scissors, cut the negative tag (arrowed below) close to the battery or about half way between the battery and PCB. You might need to twist the battery and tag slightly to get the scissors in position.
Untwist the tag if it got significantly bent.
Compare the original battery to its replacement from ToothbrushBattery.com here. This is a 2.4V NiMH 56mm x 17mm battery made up of two shorter 1.2V cells. Your original battery might be either Ni-Cd (NiCad / NiCd) or Ni-MH (NiMH) chemistry, but both can be replaced with a NiMH battery. To maximise the lifespan of your new battery see our electric toothbrush care tips here.
Bend the positive tag to shape so it matches the original battery. Bending the tag over the tip of the screwdriver might help get neat bends. Then trim the tag to length using the scissors.
Using the tip of the scissors narrow down the width of the positive tag. Carefully cut in from the side of the tag, then down from the top.
Cut off the end of the negative tag level with the edge of the battery.
With the soldering iron and some solder, quickly tin the upper surface of the tag that is still attached to the toothbrush. Don’t hold the soldering iron tip in place for too long or you risk detaching it from the PCB.
Bend the negative tag on the battery away from the battery surface a little.
Tin the battery’s negative tag. Apologies for the blurry photo!
Insert the positive end of the battery into its holder, ensuring the tag goes through the hole in the PCB.
Push the rest of the battery into its holder and slide it up towards the head end as far as it will go.
Check that the positive tag has come through the PCB hole, then fold it over and solder it into place.
Fold the negative tag from the PCB up so it is touching the negative tag on the battery.
With the soldering iron, quickly heat the joint so the two tags become soldered together. Don’t hold the soldering iron tip in place for too long or you risk melting too much of the battery’s plastic covering.
You can now press the power switch (arrowed below left) and check that the toothbrush turns on. If it doesn’t then check your solder connections. It might just need 10 seconds on charge once reassembled to ‘reset’ the brush.
Hook the charging coil wires back in place.
Slide the inner workings of the toothbrush back into the handle casing. Make sure there is no debris inside blocking it.
Ensure the innards slide all the way in so the collar (arrowed below) protrudes from the casing.
Without pulling on the coil wires, carefully put the toothbrush back on the charger. Push down on it so the cap fits into place then turn it clockwise so the latches in the cap lock it into place.
You should now have a fully reassembled and repaired Sonic Complete 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.