Important: This guide is ONLY for the Braun Oral-B Sonic Complete 4729!!! Not for ANY other toothbrush of the Braun or any other brand!!!

The battery of my toothbrush died and i have to replace it cause its a shame to throw away a electronic device just because the battery is death. I already opened it to see what kind of battery sits in there.

Now i ordered some replacement NiCd batteries and have to wait until they arrive. Probably NiMH batteries could be used too, at least they have same voltage but there might be some problems with the charger cause NiMH batteries can explode if overcharged.

NOTE: There are some very thin wires inside the toothbrush and you may destroy your device while "Repairing" it. But who cares if the manufacturer says your only option with a death battery is to bring the device to a recycling facility.

NOTE: Check your local regulations for recycling toxic waste (NiCd-Batterys)


  1. Push the bottom of the toothbrush against the knob on the back of the charger. Turn counter clock wise and the bottom should pop off. Put the toothbrush top down on a hard surface and push the inner part out.
    • Push the bottom of the toothbrush against the knob on the back of the charger. Turn counter clock wise and the bottom should pop off. Put the toothbrush top down on a hard surface and push the inner part out.

    • Be careful with the thin wires connecting the bottom cover to the circuit board.

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  3. Remove the old battery pack.
    • Remove the old battery pack.

    • The Batteries are soldered to the circuit Board. You can use your soldering iron here if you like but i think its not really needed. And probably the minus is quite hard to work on because it lays under some other stuff (fig. 3; The circle marks the minus and the square the plus connection).

    • If you're not using a soldering iron you have to peel off the wire guard from the old batteries to remove them cause they are your connectors for the new batteries. The spring in the bottom cover provides enough tension to keep the battery in place and connected without soldering.

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    • Insert new battery pack.

    • If you unsoldered the old battery from the circuit board you have to solder the wire guards from the new Battery pack to the circuit board.

    • Otherwise just insert the new battery pack and reassemble the toothbrush. I used a pice of cardboard to make sure the plus gets proper connection (fig. 1).

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Linea Traguardo

Altre 4 persone hanno completato questa guida.


Membro da: 20/03/2013

1.187 Reputazione

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what is the replacement battery and where can

I get it?

Ron - Replica

Hello Ron,

if you put: " Sanyo 2/KR-600AE 2/3 A Cadnica NiCd Battery Pack 2,4 V " into a search machine you should be able to find a replacement battery for this type.

At least thets how i got mine...

Kind regards Andy

ndjenny -

Do you need to buy 2 of these batteries? It looks like two separate batteries end to end.

Rob - Replica

sorry for the late reply. No you don't need two batteries. Actually its a 2/3 A battery that means its 2/3 as long as a full A-size battery. in my case they delivered two 1/3 A batteries in one shrinking wrap but there are also 2/3 A batteries in one piece.

ndjenny -

I /think/ any "2/3 A" size battery should work - I've ordered some NiMH ones with nearly double capacity - I anticipate that these will hold more, but take longer to charge up.

Chris Murphy - Replica

Keep in mind that the charger is not made for NiMH you must not overcharge a NiMH battery otherwise it may explode… So you do it at your own risk! Regards Andy

ndjenny -

NiMH charge at such a slow rate in this induction charger (24 hours is the norm for the first charge) that likely it will dissipate excess energy as heat.

unberger - Replica

How has this fix been holding up for you over time?


viator - Replica

Hello Tom,

the battery replacement worked very well but after sometimes the Toothbrush stopped working cause there was a crack where, i assume, moisture entered the housing and killed the electronics. So the new battery was still in good shape but the brush sometimes refused to turn on. It was to much hassle to finde the fault , thats why i replaced it last January.

Kind regards Andy

ndjenny -

Thanks for the response, Andy.

Could it have been because you didn't solder the connections?

Or are you fairly certain that it was a moisture intrusion issue?

viator - Replica

Hello Tom,

i'm quite sure it wasn't caused by not soldering the battery in. It still worked but sometimes i had to push the button many times before it started stopped running and sometimes it started running by itself. there was also much of this white stuff all over the electronics which is a sign of water/moisture damage. I owned this brush vor over ten years and i not disappointed with it's quality taken in to account how many times it dropped to the ground. If you think about replacing the battery on yours, go for it. Its easy to do, inexpensive and if your brush has no cracks it should work until the replacement battery dies. I don't think its necessary to solder it to the board.

Kind regards Andy

ndjenny -

About the question NiCd batteries or NiMh; also use a NiMh battery in their tutorial.

I think the toothbrush does have an overcharging safety build-in. The toothbrush stops charging automatically after a few hours. The charging indicator light also stops pulsing then.

Peter Bakker - Replica

I have a 4717 Sonicare Complete, would anyone know of I can go without using a Soldering iron, since I don't have one? Thank you in advance.

EricJL - Replica

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