Braun Oral-B iO Toothbrush Battery Replacement

In this battery replacement guide we will show you how to open up and dismantle the Braun Oral-B iO series of toothbrushes and repair them by fitting a new replacement Li-ion battery. These are expensive, high-end toothbrushes so it is well worth fitting a new battery to bring them back to life.

This battery replacement guide is only for Oral-B iO series toothbrushes. This includes the iO4, iO5, iO6, iO7, iO8, iO9 and iO10 models. These are marked with one of the following ‘Type’ numbers on the bottom of the handle: Type 3753, 3758, 3769, 3776 or 3794. Click the photo below to see a larger version of where the type number is marked on an Oral-B iO toothbrush:


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

The basic repair method is:

  • Open up the toothbrush handle
  • Slide out the inner workings
  • Remove the original battery
  • Clip in the replacement toothbrush battery
  • Reassemble the handle

The Oral-B iO series toothbrush battery replacement process is documented in detail below along with lots of photos. Click on any photo to enlarge it.



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 and safety precautions.

Tools, Parts & Equipment

  • Braun Oral-B iO series electric toothbrush
  • Original charger (either the circular magnetic charger or the oval Type 3757 charger with central peg)
  • Medium sized, blunt, flat-bladed screwdriver: 4 to 6mm wide
  • New replacement Li-ion battery. Support us by buying yours from ToothbrushBattery.com here


To begin, remove the brush head from the top of the handle.

Starting at the front of the metal retaining ring, use the flat-bladed screwdriver to gently pry the ring up and away from the body of the handle. A screwdriver with blunt corners is less likely to mark the toothbrush.


Store the ring somewhere safe until the end of the repair procedure.


Optionally stand the toothbrush in hot tap water for 5 minutes to soften the seal and plastic latches.


Dry the toothbrush and pick up the unplugged charger. If your iO toothbrush came with a circular magnetic charging base use the 3 tabs on the underside of the magnetic charger to engage in the 3 notches on the base cap of the toothbrush. Notches are arrowed below.


For iO toothbrushes that come with oval chargers with a central peg stand the toothbrush on its unplugged charger.


Turn the toothbrush approximately 45-degrees anti-clockwise (an eighth of a turn) against the charger. You will feel the base cap come unlatched.


Bend the toothbrush back a little to create a gap and release the seal slightly.


You can now lift the handle off the charger. The base cap might stay on the charger.


If the cap stays attached to the handle casing you can then pry the cap out by hand. Be careful not to lose the spring!


Holding the handle casing push the grey head connector down inside the casing. The grey rubber seal might fold inside the casing but this is fine.


The internals of the toothbrush will start to emerge from the bottom of the handle.


Below you can see the removed inner workings of your Oral-B iO series toothbrush:


Turn over the innards to see the internal rechargeable battery in its holder.

Note the + sign on the battery indicating the positive end of the battery. There is also a groove around the circumference of the battery at the positive end, arrowed below.


With the blunt screwdriver pry the battery out. There is a convenient gap in the holder at the side of the positive end.


Note the + symbol moulded into the white plastic of the battery holder to indicate the positive terminal, arrowed below.


This battery is a 49mm long, 14mm diameter 3.7V Li-ion battery with a flat top made by Sanyo. Please support us in writing these repair guides by buying your new iO battery from us via our Oral-B iO toothbrush battery shop page.


We recommend only using well-known brands of Li-ion battery such as Sanyo or the Braun OEM batteries for safety, reliability and long life. Batteries of this size from Sanyo and Braun have true capacities in the 600-800mAh range. There are generic/unbranded batteries available which claim huge capacities well over 1000mAh. These are false claims and the batteries can have a real capacity less than 300mAh when tested! No manufacturer makes a 49mm x 14mm Li-ion battery with a real capacity that high.

Genuine Sanyo Li-ion batteries for iO toothbrushes are available from us at ToothbrushBattery.com here, as pictured below.


Genuine Braun OEM Li-ion batteries for iO toothbrushes are also available from us at ToothbrushBattery.com here, as pictured below.


Below is a photo of an unbranded battery with a falsely claimed “1500mAh” capacity printed on it. No manufacturer makes this size of battery with a real capacity that high so avoid these unbranded fakes. This one had a real capacity of only 255mAh when we tested it:


Making sure to observe the correct polarity (+/-) for your toothbrush, insert your new Sanyo or Sony replacement iO battery in the battery holder. It is possible to install the battery the wrong way round so be careful to get this right or you might permanently damage the toothbrush’s circuitry.


You might find that the toothbrush’s display lights up when you turn it over.


If the display does not light up then hold the brush securely at the sides of the frame and press the power button once (arrowed below) to check that the screen comes on and the new battery is working.


You can alternatively hold the internals on the plugged-in charger to verify that it wakes up if you wish.


Wait for the screen to turn off then check that there is no dust or debris on the screen as this might be visible through the outer casing after reassembly.


Slide the internals back inside the handle casing. You should not need to force it so if it does not slide in easily check the alignment of the internals within the grooves inside the casing.


As the grey head-holder emerges through the top of the casing it should fold the grey seal out.


Make sure the grey head-holder is fully proud of the seal so you can see where the grey ridge widens towards its bottom, arrowed below.


Put the spring back on its + shaped peg inside the bottom of the handle.


Partially insert the base cap back in place so the black seal is still visible. If you push it all the way in it might pop back off due to the spring pressure. Make sure you get the cap’s orientation correct. The printed “Li-ion” and “CE” text is rotated 45-degrees anti-clockwise.


Stand the toothbrush on its charger and push it downwards so the base cap is fully seated.


While holding the charger still, turn the handle 45-degrees clockwise to latch the base cap in place.


Plug in the charger to check that the toothbrush indicates that it has started charging.


Finally, clip the metal ring back over the seal. Position the back of the ring first then clip the front edge in place.


You now have a fully repaired Oral-B iO toothbrush!


Give your brush a full charge then it will be ready to use.

Please recycle your old battery. It is safest to put sticky tape over at least one end of the battery 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 iO toothbrush battery replacement guide below. Happy brushing!

Frequently Asked Questions

Can I replace the battery in my iO series Braun Oral-B toothbrush?

Yes you can replace the battery in every Oral-B iO toothbrush, including the iO3, iO4, iO5, iO6, iO7, iO8, iO9 and iO10 models, without any specialist tools. Follow our guide on how to open up your iO toothbrush handle and replace its internal rechargeable battery.

Which replacement battery do I need for my iO series Braun Oral-B toothbrush?

The type and size of replacement battery required for the Oral-B iO series toothbrush is listed in the Tools, Parts and Equipment section of our guide above.

I have a different model of toothbrush. Can I replace the battery in that?

Yes take a look at our list of toothbrush battery replacement guides to see how to replace the battery in various models of electric toothbrush.

15 thoughts on “Braun Oral-B iO Toothbrush Battery Replacement

  1. Many thanks for your guide… very informative. Our 7 month old Oral B io just stopped working but was still live but with the white light beneath the power switch flashing rapidly. The receipt is unfortunately lost, so thinking this was a battery issue I dismantled it and replace the battery which I bought from you (arrived this morning) and is identical to the original Sanyo battery.

    Unfortunately this did not repair the problem and the symptoms are the same. There is no obvious fault on the circuit board and no corrosion to be seen – everything seems brand new. Any help you can offer gratefully received. The model number is 3794

    1. Even without the receipt you might still be able to return it to the shop you bought it from as faulty, if you have the bank/card statement. Otherwise the UK service centre for Oral-B (Olympic) might still repair it under guarantee as they can tell its age from the serial number.

  2. Followed the instructions including soaking in water but turning toothbrush on the oval charger base does not work. It just does not turn at all. Is there anything that can help to release the base so I can change the battery?

    1. The joint between the base cap and the handle body might be caked with toothpaste so if you can scrub this out it might let you turn the base cap. Otherwise you might have to resort to tools. Do use padding/cardboard/tape to prevent too much marking of the plastic.

  3. instructions are simple and effective , toothbrush came apart after a hot soak , unfortunately using a battery tester , the battery was fully charged . reinserted the battery and tested for power at coil at the head of the toothbrush .Result was no power however the button was pressed so must be circuit board . my io 4 is around 14 months old and I don’t have the receipt what are the chances of repair

    1. If your battery tester is for standard AA batteries it will give a false reading when a high-voltage Li-ion battery is put in it. A healthy Li-ion cell will be over 3.0V when empty and just over 4.0V when full.
      You might find that your toothbrush is under a 2 year guarantee. If you contact your regional Oral-B service centre they can normally tell you from the brush’s serial number if it is under guarantee still.

  4. Thanks for a very useful guide, and also for the info on the differences between genuine and poor quality batteries. I have ordered a battery today from you.

    1. Glad to hear the guide was useful, and thank you for your order.
      Let us know how the repair goes!

  5. Thank you for the very clear instructions.
    Following a full charge the toothbrush kept going off with the low battery -red light flashing. After removing the original battery (740mAh), testing with a multimeter is showing 3.91V. Does this mean battery is ok?

    1. 3.91V indicates a Li-ion battery that is nearly fully charged. The low-battery light could indicate a fault with the internal circuitry. Are there any signs of water ingress such as staining on the PCB or rust?

      1. Doesn’t appear there has been any water ingress. Probably circuitry issue. Toothbrush is 3 years old – so unfortunately no warranty.

  6. Absolutely chuffed with this guide! Bought an iO7 a few years back and the battery was only lasting about 30 seconds, not great from a £££ toothbrush. Bought a battery from you, followed the guide (which was super easy) and it’s like new again! Thanks so much!

  7. Fabulous!!! Thank you

  8. Really pleased with this guide. Bought a new battery for my iO8 toothbrush from you, it came the next day. Followed these instructions which were really easy to follow and now toothbrush works like brand new,. Thank you, saved me some money here from buying a new iO toothbrush

  9. Hey guys, replaced my battery – everything was working well but after a few days my screen stopped working. I miss that smiley face 🙁

Leave a Reply
Any comments containing links are automatically deleted. Your email address will not be published.