Braun Oral-B Pro/Smart Type 3766 & 3767 Battery Replacement

This guide will show you how to open and dismantle the Braun Oral-B type 3766 and 3767 electric toothbrush models and repair them by fitting a replacement Li-ion battery. These are great toothbrushes so they are well worth resurrecting with a new battery.

This battery replacement guide is only for Pro and Smart toothbrushes from Braun Oral-B that are marked as either Type 3766 or Type 3767 on the bottom. These brushes are fitted with a Lithium-ion battery (Li-ion). Click the photo below to enlarge it and compare the ‘Type/Tipo’ number marking to your toothbrush:

Braun Oral B Type 3766 3767 toothbrush type number

Also note the ‘Li-ion’ marking under the recycle symbol in the bottom of the hole.

For other type numbers, makes and models the toothbrush opening and battery replacement procedure is different so please see our other guides to toothbrush battery replacement for these toothbrushes.

The Type 3766 and 3767 toothbrushes from Oral B/Braun go by many different names on their packaging including Pro 2, Pro 3, Pro 4, Pro 600, Pro 1000, Pro 1500, Pro 2000, Pro 3000, Pro 4000, Smart 4, Smart 5, Smart 1000-6000, Smart Teen, Smart Junior, Smart Professional and often have ‘Professional Care’ marked on the handle itself. The only reliable way to tell which model you actually have and therefore the best guide to use for replacing the battery is to check the type number marked on the bottom of the handle as shown in the photo above.

The basic method is:

  • Open up and dismantle the toothbrush handle
  • Desolder PCB connections
  • Remove the PCB and the original battery
  • Solder in the replacement toothbrush battery
  • Reassemble the handle

The type 3766 and 3767 toothbrush battery replacement process is documented in detail below along with lots of photos. Click on any photo to enlarge it.

Braun Oral B Type 3766 3767 toothbrush handle


Any damage or injury to yourself, your toothbrush or anything else is entirely your responsibility. This guide is for professional, educational usage only and is offered without guarantee or liability. Lithium-ion (Li-ion) batteries are dangerous if short-circuited or mis-handled and can go into thermal runaway and self-ignite if you do not observe all handling precautions.

Tools, Parts & Equipment

  • Braun Oral-B Pro/Smart type 3766 or 3767 electric toothbrush
  • Original charger
  • Soldering iron with fine needle/cone tip: Electronics grade (about 18-25 watt)
  • Solder: Lead-free silver solder with a flux core is recommended
  • Solder sucker (also known as a desoldering pump) and/or desoldering braid/wick
  • Craft knife e.g. scalpel, snap-off, retractable or Stanley type
  • Large blunt flat-bladed screwdriver: 5 to 7mm wide
  • Needle nose pliers
  • Miniature side cutters
  • Adhesive putty such as Blu Tack to hold the toothbrush to the work surface
  • Replacement Li-ion battery: Support us by buying yours from here


To start with, remove the brush head from the top of the handle and stand the toothbrush, tip downwards, in hot tap water for 5 minutes to soften the plastic ring.


Using the large flat-head screwdriver start to pry off the plastic ring from around the shaft. The ring is stepped so press down into the soft casing to get under its lower edge. A screwdriver with blunted edges is less likely to mark the toothbrush, and prying from the back side of the handle will hide any marks.


Store the removed ring safely.


Stand the toothbrush in hot water again, tip upwards this time, for another 5 minutes to soften the seal around the base cap and the cap’s internal plastic clip.


Dry off the handle with a towel then stand it on its unplugged charger.


Carefully bend the toothbrush backwards so the base cap is levered open at the front.


Lift the toothbrush off the charger and remove the base cap. The spring might fall out and roll away so don’t lose it!


Push the top metal and plastic shaft into the main body of the toothbrush handle so that the toothbrush innards start to slide out.


Fully remove the inner workings of the toothbrush from its handle casing.


The power switch cover plate needs removing. It clips into two holes on each side, arrowed below. Unclip the plate from its holes on one side first, then the other, to remove it.


Now’s the time to warm up your soldering iron! A soldering iron with a fine needle/cone tip is recommended for working on these toothbrushes.

Arrowed below is the battery’s negative terminal connection.


Remove some of the solder from the connection using the soldering iron and a solder sucker or braid. Then reheat the solder joint and using a knife blade lift and bend the solder tag so it is vertical.


Desolder the two connections for the wires from the pressure warning light, arrowed below, and lift them away from the solder pads. Take care not to melt the white plastic wire carrier.


Unclip the carrier from both sides of the PCB.


Fold the carrier away from the main mechanism and slide it off the top of the toothbrush.


Desolder the connection for the pressure switch from the PCB as arrowed below.


Unclip the pressure switch from near the solder connection end then gently lift it up and out. It is hooked in at the other end.


Desolder the two motor connections, arrowed below, and fold them up and away from the PCB.


Desolder the positive battery terminal and fold it upwards away from the PCB.


Turn the toothbrush over and inspect the white plastic battery carrier. It is held in place by two tabs in the metal frame.


Gently pull the plastic battery carrier along the metal frame while using a screwdriver to pry the plastic up and over the metal tabs, one side at a time.


Slide the battery carrier off the metal frame.


Release the clips holding the black coil carrier to the battery carrier and bend the coil carrier away slightly.


Release the clips holding the PCB to the battery carrier.


Lift the PCB off the battery carrier.


You can now slide the battery out of its carrier. Be careful not to short-circuit the two terminals on anything metal.


Compare the battery to its replacement as shown below. These are 49mm long, 14mm diameter 3.7V Li-ion batteries. Please support us in writing these repair guides by buying your new battery from us at here.


Positive terminals:


Negative terminals:


A gap needs to be opened up between the PCB and the coil carrier for the pin on the new battery.


Melt the solder on the two coil wire connections and slide the coil carrier back a little to create a gap for the pin.


A notch needs to be trimmed out of the battery carrier to make room for the positive battery pin. Use a craft knife to shave away the plastic.


Bend the negative pin slightly as shown below. Grip the pin below where the bend will occur with needle nose pliers and bend the pin above the pliers so you don’t shear the pin off the battery.


Slide the new battery into the battery carrier so the negative pin ends up vertical and the positive pin is aligned at angle with the notch.


Slide the PCB and coil carrier over the battery pins and onto the battery carrier.


Clip the PCB onto the battery carrier starting at the postive end (left side in the photo below)


Using the miniature side-cutters cut the negative pin level with the top of the black plastic of the coil carrier.


Cut the positive pin to a similar length.


Slide the battery carrier onto the metal frame of the toothbrush and check it latches into place.


Fold down and solder the two motor terminals to the PCB.


Create a solder bridge between the battery’s positive pin and the solder pad on the PCB, making sure the pin is heated sufficiently so the solder forms a good join.


Fit the pressure warning light carrier to the top of the brush and clip it into place.


Solder its two wires to the PCB, trying to avoid melting the white plastic wire carrier.


Clip the front of the pressure warning switch in place.


Clip the rear of the pressure warning switch in place and solder it to the PCB.


After visually checking the PCB for any stray blobs or whiskers of solder you can now make the final battery connection.

Create a solder bridge between the negative battery pin and its PCB pad.


The PCB is now ‘live’ and you can test the new battery by switching on the toothbrush. Hold the brush firmly on either side of the motor then press the switch to turn on the brush.


If the toothbrush appears to be dead you might need to ‘reactivate’ the circuitry by standing the assembly on the charger for 5 seconds. It should light up and start charging. Then you can remove it and try the switch again.

Clip the switch plate back in place, one side at a time.


Slide the innards of the brush back inside the handle.


Make sure the innards are pushed in fully so you can see the groove for the ring at the top of the handle.


Clip the base cap back into the handle, hooking it in at the back first.


Heat up the ring in some hot water for 30 seconds, dry it, then push it back into place. You can use a 10 or 11mm spanner, or an old brush head to force it on if necessary. Make sure it is fully clipped into place.


You now have a fully repaired Braun Oral-B PRO or Smart toothbrush!


Give the toothbrush a full charge then it’s ready to use.


Please recycle your old battery. It is safest to cut or pull the tags off it with pliers then put sticky tape over at least one end to avoid short-circuits. You can then take it to your local supermarket battery collection point or civic recycling facility.

Please leave any comments, questions or suggestions about this Braun Oral-B Type 3766 and 3767 battery replacement guide below. Happy brushing!

1 thought on “Braun Oral-B Pro/Smart Type 3766 & 3767 Battery Replacement

  1. Is it possible to buy a motherboard for this toothbrush? Apparently the battery and engine of my toothbrush seem OK so I suspect the motherboard might be broken.
    I looked for V3 D601 4L all over the internet but didn’t find any.

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