Oral-B Sonic Complete Toothbrush Battery Fix




This project shows you how to replace the batteries in an Oral-B Sonic Complete toothbrush. This is a great electric toothbrush, but Oral-B tells you to toss it when the internal rechargeable Ni-CD batteries die. Aside from the wastefulness of that, the toothbrush costs about $90. So, when my father's toothbrush finally died, we decided to replace the batteries anyway. This project requires soldering, and there's some risk you'll destroy your (presumably nearly dead) toothbrush when taking it apart and putting it back together.

Step 1: Supplies

The key here is ordering the battery. We found ours at the NICD Lady, a Sanyo KR-600AE with solder tabs. As of 7-29-2009, you could find it on this page:

As far as I can tell, all NiCD cells are 1.2 volts, and this one appeared to be almost exactly the right size. Since the toothbrush can hold enough charge when new to go for a week without recharging, we figured that even if these didn't exactly match the capacity of the original NICD cells, they ought to work.

Because the device was designed for NICDs, you ought to replace the battery with a NICD.

Beyond that, you need a soldering iron, solder, maybe an X-acto knife, some long-nosed pliers, a hemostat (we used a paperclip instead), and some electricians' stable.

Step 2: Take the End Cap Off the Toothbrush

STOP: You need to know two things before proceeding. First, the innards are spring-loaded. Second, the base of the toothbrush remains connected to the body of the toothbrush with four THIN copper wires. These are fragile. So, you need to keep a tight grip on the toothbrush when you do this step.

The "wrench" for unlocking the base of the toothbrush is on the back of the charger.

Get a good grip on the toothbrush, push it onto this "wrench", and give it a slight twist while pushing it solidly into the charger. It takes little effort and about an eighth-turn to unlock the toothbrush bottom. When you feel it pop, gently remove the toothbrush. If the base of the toothbrush sticks to the charger, get a screwdriver or other small instrument in there and gently pry it loose. Don't try to pull it off via the four thin copper wires.

Step 3: Remove the Innards

The entire insides of the toothbrush will come out at this point. The bottom edge of the internal "works" engages the outside plastic casing. So you may want to reach up with needle-nosed pliers or a small screwdriver and pry the edge of the inside "works" away from the outside casing, as you push the "works" out from the other end.

To be clear -- the entire thing comes out, so push the steel rod where the brush attaches, as you disengage the bottom end of "the works" from the exterior casing. This does not require a lot of force. Once it's free, its just the friction of an O-ring seal at the top that is holding the works in.

Step 4: Remove the Old Batteries

The batteries are soldered in. There are only two rules here: 1) Leave as much of the solder tab attached to the circuit board as you can, and 2) don't break anything. You'll see why you want to leave the solder tabs on the board when you go to put the new batteries in. Beyond that, you're on your own. I used a combination of long-nosed pliers and an X-Acto knife to pop as much of the tab off the battery as possible. Good luck... Trust me, take the time to leave as much of the tab on the board as possible. You will thank yourself as you go to solder the new batteries in.

Step 5: Solder the New Batteries Together,

OK, so I did this exactly once in my life. I am sure I could do better with practice, but here are the rules.

First, and dumbest, solder the batteries together POSITIVE to NEGATIVE. The positive terminal has the bump on it, just like a regular AA. I laid the batteries out side-by-side, clipped the leads together, and soldered. Then just fold the mess together as tightly as possible and put a bit of tape on it to hold it together.

Step 6: Solder the New Batteries Into the Casing

Then, when you have the pack together, the POSITIVE lead goes up into the case, the NEGATIVE lead is soldered to the tab at the bottom of the case, near the four fragile wires.

It's a major boo-boo to get that wrong, so check it a couple of times.

As to how you get the battery tabs soldered to the stubs, all I can say is, I did the one in the middle of the casing first, folded up the tab, and then did the one at the bottom. The tabs need to lie nearly parallel to get a good solder join -- but then you can just bend the excess out of the way.

For what it's worth, the standard advice is, don't overheat the battery when you do this. How you'd know the battery is overheated, don't ask me. Anyway, the goal is to get solid solder joints between the battery tabs and the stubs of the tabs that are attached to the circuit board. No style points -- any way you can manage that is OK.

Step 7: Re-assemble

Insert the works into the case. DO NOT FORCE IT. The picture shows the proper orientation. (Forgot, didn't you? I sure did.) If in doubt, look down the top of the case, and the rod that holds the toothbrush will be centered in the hole if you have the whole works oriented right. Took me a few tries.

Now, here's where you may break one of the four small wires. (I did, and just soldered it back into place).

The hardest part of the entire deal is re-assembling the bottom. Hold the toothbrush upside down by the case, assemble the parts (with the "turning" part of the toothbrush bottom in the open (one-eight-turn-askew) position. What you have at this point looks like an exploded diagram of the bottom of the toothbrush. Make sure the four thin wires look like they are resting comfortably. Now hold the charger wrench facing downward, engage the upside-down toothbrush with the wrench, gently compress the mess, and turn it back one-eighth turn to tighten.

If all goes well, hey, that's it. If not, it'll take you three or four tries (as we did). We (my dad) broke one of the wires at that point, had to solder it back -- might be worthwhile taking a look at those before you start this step, just in case.

But all's well that ends well. Plug in the charger, put the brush on the charger, and see if it'll charge. Blinking light? All is well. After a couple of minutes, you can briefly turn it on to verify that it works. Then let it charge.

Step 8: Epilogue

Dispose of the NICD batteries as toxic waste, please. That's what you're supposed to do, and that's why the case opens up in the first place -- you're supposed to pull the batteries before you toss the device.

Bottom line: $5 worth of batteries, $3 shipping, and an hour of labor saves a $90 toothbrush. No idea how long this will last, but it seemed worth the gamble.

Finally comments: Probably should have replace the O-ring seal at the top while I was at it.
And, if you're going to be photographing your toothbrush for viewing on the internet...

...Clean it first.



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    22 Discussions


    5 years ago on Introduction

    This is great :) Got my Braun Oral-B electric toothbrush up and running again and now it lasts as long as when it was new! I was a bit worried about the quality of cheap generic unbranded batteries and how long they'd last in terms of recharging cycles, so I got branded ones from  http://toothbrushbattery.com and they've been working brilliantly. I'll try and do a link to the website toothbrush battery shop there I hope that works!
    I soldered mine in by the way.


    6 years ago on Introduction

    I coudn't believe I had to ditch my toothbrush because of dud batteries. Glad to find lots of very helpful advice on the web. I got 2 NiMH 2/3AF, 2/3A equivalent batteries from Batteries Plus Ltd (UK) for £5.45 inc postage. I followed one person's advice to 'peel' the tags off the old batteries, to provide contact for the tags on the new ones. I folded the tags over to provide a bit of a 'spring' to ensure good contact. I was prepared to do some soldering but considered it completely unnecessary. After all, we use 'loose' fitted batteries every day in stuff, with no problems, and the coiled spring in the handle of the toothbrush has plenty of muscle to keep the batteries in contact! After a full charge, I have left the toothbrush off the charger to see how long it holds charge for with daily use by two people. It should be longer than with the original batteries, so I'm not holding my breath.


    6 years ago on Introduction


    I actually followed the original instructions and soldered the two batteries together and soldered both ends. I put everything together and put the brush back on the charger. The blue light immediately started blinking stating the battery was charging. Well, it's been blinking for the past two days. When I turn it on, it works for a quick second and then stops. Anyone have any idea on why it's doing this? Any advice/help would be greatly appreciated. Thanks.


    6 years ago on Introduction

    If you break the wires, all is not lost - read on!
    If you can, buy batteries up front. I took apart mine to check size of batteries etc. It will save all the dismantled bits lying around and being knocked around, and if you have the battery to hand, what you did dismantling it etc are still fresh on your mind.
    For an Oral-B Sonic Complete the batteries you need are 2/3A. I thought this referred to 2/3 of an Amp, but it is actually the model no.! Using 2/3A returns far more results in searches. I got 10 for 17USD with free shipping from a vendor in Hong Kong! Shipping was a bit slow taking almost 3 weeks mind.
    I would tape the base to the inside frame once dismantled, that way the wires won't get twisted and twisted some more as you work on it (or leave it lying about waiting for the batteries to arrive like I did).
    In joining the 2 batteries (I soldered - not very well - then taped the join to make it more rigid, but probably OK if they both have tabs and you just tape together with thin tape) pay attention that the tabs on the remaining ends 'align', the +ve with the hole and the -ve can make good contact without having to twist it. I didn't solder the -ve end, just made sure the tabs made good contact - plus remember there is the spring to push it against the -ve terminal.
    There are 3 soldered connections with 4 fragile wires leading to the base, the central having 2 wires. If any 1 breaks then solder to the terminal from where it came to maintain the 1.2.1 configuration. If more than one breaks, then chances are you are in a bit of a pickle as you don't know which wire goes where (unless you have ended up with 0.2.0 or 1.0.1, when it does not matter how you maintain the 1.2.1 configuration). I was not so fortunate and eventually after lots of trail and error (put it back together not charging) wires coming loose from soldered terminals, 3 wires came loose with 1 of them broken and too short. Which called for drastic actions...
    I unsoldered the last connection so the base was completely detached. There is an inner core to the base which can come away from the encasing shell. I unwound the wires and found it is actually 2 wires - hence 4 ends. I rewound the wires, but not completely, so that I have 4 decent lengths of wires to work with. I paired the ends (my batteries came with plastic +ve strip insulators - cutting a bit off worked a treat in keeping 2 ends paired) so I knew they belong to the same wire. Plug the core (solenoid) back into the base shell. You then solder the end of one wire to make 1.0.0, take the other end of the same wire plus an end of the other wire and solder to the middle making 1.2.0, and finally the remaining one solder to make 1.2.1).
    For the physicists among us, the base of the stand must have an electromagnet, inducing a current in those thin copper wires and charging the batteries.
    And there we have it! Even if the wires break, the job is still salvageable!


    6 years ago on Introduction

    Thanks for this. Worked fine. Notes:

    1) I bought two tabbed 2/3A NiMH batteries. 2/3AF is also a valid size. You can get these online at lots of places. They do not have to be NiCD, and they do not have to specifically say "KR-600AE" or "KR-600AE replacement". Just get two of any NiCD/NiMH battery that is 2/3A or 2/3AF size and tabbed an they will work just fine.

    2) I will repeat what others have said above - do NOT cut the tabs. Use a razor blade and a small flat-head screwdriver to pry the tabs off the batteries. Go slow, and start with the blade.

    3) I will also repeat what people said above about not soldering the batteries together. I folded up the tabs, and while exerting lots of pressure on them and holding the batteries together, I got someone else to wrap strong tape firmly around both batteries.

    4) I did not do ANY soldering at all (I am not very good with a soldering iron, and I wanted to do it in such a way that I could easily disassemble things later if I needed to). I simply used folded up pads of aluminum foil (an excellent conductor) at placed them at either end to ensure a good contact. The tension of the spring in the base is quite high, so it ensures that as long as you do it up properly, the contacts at the bottom, between the batteries and at the top will remain secure an pressed together even without any solder. If you are good at soldering, then go ahead, but I don't think it's necessary.

    Hope this helps.


    6 years ago on Introduction

    This works great! Thank you for saving me some $$. The batteries have changed model numbers but the website points you to the right ones. Saving the leads is key and there is no need to use solder. If you bend over the leads and tape the batteries together the spring holds it all together when you put things back together.

    easter egg

    7 years ago on Introduction

    I broke my thin copper wires off. Does anyone have a close-up picture of this section or a schematic? I have 4 wires but I only see 3 point to solder. Does one of them need 2 wires?

    1 reply
    fixthis23easter egg

    Reply 7 years ago on Introduction

    There are massive guides, batteries and howtos available under www.epmtec.de hope could help you out.

    By the way: also in the Netherlands you can buy the two battery pack with soldering leads. Very easy to install following the instructions with this type.


    7 years ago on Introduction

    Great instructions! Replaced mine and my wife's batteries and have another set ready for the next toothbrush that fails. All for less than $20 including shipping to fix $300 worth of toothbrushes. Used http://www.batteryprice.com You can get the batteries with or without soldering tabs already on them.


    8 years ago on Step 7

    Excellent intructions! Thank you!


    8 years ago on Step 5

    My professional oral B 6000 has only one battery. I presume I only need to replace one. I am not sure what soldering means. Do I need to burn it? The top lead has been left attached to the main unit while I pulled the battery out. I want to know if I need to solder the new one, or can I just insert a new battery in and hold the lead will somehow touch and make a connection without soldering. Also, I have broken one of the four wire while pulling out the thing. I don't know how to solder back what seems to be a thin wire. Will toothbrush work with three wire? Anyway to go around it? Can I twist a connection wire around it or something? Please help! Thanks.


    8 years ago on Introduction

    Your instructions were really useful Paul. I would only add the following: 1) Prying the tags off (see psj above) is really sensible 2) Soldering the batteries together is tricky. If I do it again I will try dry contact, as the spring in the base exerts a lot of pressure 3) Essential to tape the batteries together before you insert them, otherwise the spring tries to force the joint upwards. If you are in the UK, I got my batteries from: http://www.budgetbatteries.co.uk/ and they only cost £5.52 including shipping.


    8 years ago on Introduction

    Excellent post. A you tube search on 'How to Solder', £8 for an ebay solder kit. £8 for batteries incl post. Half hour following your very precise instruction....and a working toothbrush. Now waiting for a battery for my dead Bosch IXO!! Great stuff


    9 years ago on Introduction

    In the UK I used batteries I purchased from maplin.co.uk. With p&p it cost £10.97 to repair. I purchased the tagged 2/3 AF NiMH 1100mAh batteries.

    It's charging up right now. Done my bit for the environment, battled built in obsolescence, and saved a few quid in the process.

    Thank you, and your dad, for the instructions.

    2 replies

    9 years ago on Introduction

     Whatever you do, DON'T CUT THAT TAPS.

    If you use a small screwdriver to pry these taps off the batteries, there will be plenty of space to solder. Use the long nose plier to flatten the taps before soldering. I got 2 Sanyo KR600AE for less than $5 with taps and welded together.

    Thanks for sharing.


    9 years ago on Step 5

    I found the Sanyo KR600AE batteries at www.onlybatterypacks.com. They also have a two cell pack with wire leads which may be easier. They also have low shipping costs.