Sonicare Battery Replacement

SonicareAs the batteries in my Sonicare toothbrush have died a slow death, I’ve been looking for a way to replace them. P. Flindt’s Philips Amazon review of the Sonicare 4100 finally provided a promising solution:

Since the warranty expired, I took a Dremel tool to the Sonicare and opened it up. To my delight, I noted that the batteries employed by the unit were two standard, albeit unbranded AA NiCad cells. I removed and replaced them with two 600mah Sanyo cells, closed the handle and sealed it shut with silicone. It’s been over a year now and my Sonicare is working as well as it did the day I bought it.

Hearing the magic word Dremel, I resolved to spend a bit of Sunday afternoon in the basement seeing if $5 of batteries could save a $50 toothbrush. Cutting through the mid-line groove of the handle took a few passes to gauge the 1/8″ depth of the plastic. The top joint, inside the threading for the brush head, isn’t easily reached for cutting, but came apart with a twist of a screwdriver from the side just below.

Inside, the unit is quite densely packed. From the base, there’s a charging coil, the two AA NiCad batteries as described, and another coil to drive the head, all covered with a small circuit board. And it’s quite solid: the whole thing is cemented into the back of the handle with a hardened Soylent Green epoxy. The batteries were not only soldered to the board and each other, but mired themselves in a good 1/8″ of epoxy.

Cutting off the portion of the back housing attached to the batteries made them more accessible. But even after drilling out some of the epoxy, they were still firmly attached. Faced with the remaining tasks of detaching the batteries, soldering in a new set, and resealing the handle and its new battery door, I admitted defeat to the integrated obsolescence of Philips’ engineers. I’ll be buying another one because it does a good job and lasted a healthy six years, but still shaking my head at the design.

View the Sonicare photos

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29 Responses to “Sonicare Battery Replacement”

  1. Fred W Grab Says:

    I saw your info on the Sonicare battery replacement and since I have a Sonicare that has a battery problem I decided to see if I do a replacement. I was able to get out the old batteries and replace them with new ones but in the process damaged the circuit board. Do you know where I could get a new or used working circuit board. Thanks for your help.

    Fred W Grab

  2. renee Says:

    Regarding replacing your old Sonicare, it looks like Philips has decided to pursue planned obsolesence…while I have friends with Sonicare toothbrushes that have lasted 4-6 years or more, most of the newer ones seem to be designed to fail in about 2 years.

  3. Joe LaGreca Says:

    I have the same sonicare pictured above and am in the process of replacing the batteries. I already bought a new sonicare from costco, so this will just be for fun and to make a backup toothbrush.

    I was able to open the body using the screw driver method, and crack the body into its two pieces. I was also able to crack the batteries free from the epoxy using only a screw driver. But worst cast scenario, I figured I could just cut the shrinkwrap off the battery, and extract the cell from within the shrinkwrap.

    The hardest part that I’m facing right now is the de-soldering of the circuit board, so I can get the batteries out. I will attempt that after I find some de-soldering braid to suck up the solder.

    Thanks for your post!


  4. Gerard Says:

    Great info as I have two of these and was a second short of throwing both into the recycle center bin. I will now attempt the replacement methods mentioned. Be advise; always use a “heat sink” when soldering around circuit boards as this will protect the delicate components from the intense heat of the iron. A simple alligator clip will suffice in most cases.
    Great posting.

  5. Rumplestilskin777 Says:

    It’s a dirty rotten shame that they design these so that a battery can’t be replaced. That should be illegal!

    It literally creates waste and pollution for profit.

    And, evidently, the new ones are designed to fail even sooner!!!

    These bastards need some competition!!!

  6. Kit Says:

    The new units are designed for the easy replacement of an OEM battery later on. My old unit similar to the one in the picture above lasted eight years of abuse. I will attempt to repair the old unit as I was using it for cleaning jewelery and small collectibles, which it did impeccably.

  7. James Says:

    so what batteries do you buy to put in there?

  8. Matthew Says:

    James, I believe they are NiCad AA batteries.

  9. Rick in LA Says:

    Your pictures helped me a lot in replacing the battery in my 7 year old Advance handle.

    I used a hot knife - a special soldering iron element that holds an Xacto blade - to cut open the body along the seams. It has to be done in multiple passes as the blade tends to melt the plastic in spots if you try to melt all the way through the 1/8″ thick plastic in one pass. I wouldn’t say it’s a cleaner way to open up the case compared to using a Dremel, just different.

    I bought a 2.4 volt AA pack designed for rechargeable electric razor use but it was suitable for the Advance. The two cells were supplied tack-welded to a connecting strip with 3/4″ long terminations at the (+) and (-) ends.

    I found it easy to just use my solder sucker (a spring loaded pump that sucks up molten solder from the joint) to desolder the circuit board from the charging and field coils and cut the existing battery wires about 1/4″ from the board. That made it possible to simply solder the new battery terminations to the board.

    After using a razor knife to cut through the plastic encasing the old battery cells, I pulled out the dead battery and clipped away some of the epoxy using a small pair of end-nippers. When everything fitted in place, I soldered it up and sealed the two halves together with bathroom silicone sealant. Put it in the charger and let it charge overnight.

    The brush now works like new.

  10. Rich Heimlich Says:

    Above “Kit” suggests the new units are designed for easy replacement of the battery. That would restore my faith in these guys as I love my toothbrush but cannot justify spending $150 on a product that only a couple years later cannot get me through a single 2-minute brushing without dying.

    I re-considered when I read the above comment. However, upon going to the Sonicare site and reading the latest product manual I see that the design has changed. The problem is, you can now remove the rechargeable battery for disposal but the process is not reversible. They tell you that this can only be done at the end of the life cycle of the product.

    Pure lunacy. This has to be their biggest problem. Come on. At least design a replaceable battery pack and let us get it from you. Throw us a bone here. We love the product but it’s a faulty design.

  11. Craig Says:

    Jeez, guys. Does “engineered obsolescence” ring a bell? Say you own Philips Sonicare and are talking to your engineering staff. You would say:
    A. Fellas, build this puppy in a way that our customers can go down to Wally World and replace the batteries for a buck-fifty.

    B. Fellas, build this puppy in a way that after a couple years’ use they’ll be so sold they’ll fork over another hundred plus so we can KEEP OUR PHONY-BALONEY JOBS!

  12. nancy Says:

    The sonicare website has instructions on how to open the housing for the purpose of recycling the batteries. I’m assuming that would be more useful than cutting it open with a dremel.
    Also, I’m sure they epoxy everything in place because it is a highly vibrating product and they want to make sure the thing doesn’t rattle itself apart.

  13. THADDEO Says:

    From all the comments I’ve read it’s either replace the Sonicare with a new one or get all the right tools to replace the batteries. By then you will have probably spent enough for a new Sonicare.

  14. Greg Says:

    I replaced the 700 mAh NiCad batteries in my sonicare with 2600mAh NimH batteries - ran the unit with a meter and watched charge cycles etc.

    Works perfect! Unit trickle charges within acceptable limits for NimH and even registers a full charge. In my case above, it logically took about 3x longer to reach a full charge, but the unit will also run 3x longer from a full charge then vs. the NiCad. Cheap and plentiful to get NimH AA batteries retail.

    Requires de-soldering of about 6 points - use a low temp solder iron, solder sucker and appropriate skills. $12 in batteries, 3 hours effort - saves me wasting a good unit that lasts three times longer run time and will be better suited charge longevity over NiCad. Pays to be a geek.

  15. Matthew Says:

    Thanks for the NiMH info, Greg! The extra run time must be great for those long vacations…

  16. Jeremy Says:

    Did the NiCd replacement but even after a full charge, the Sonicare seems to be stuck in the “intro” mode where it only runs at half power. I followed the procedure in the manual for switching modes but it doesn’t seem to make any difference. I used a set of 1000ma NiCd’s which should be plenty.

    Any ideas?

  17. Jeremy Says:

    I used a Permatex 2-part epoxy to seal the unit back up. You can’t even tell it was ever pulled apart now.

  18. Andreas Says:

    Hi guys,

    what a wonderful hint to solve this annoying Sonicare-problem. I tried it by cracking the housing with a dremel but i cut also the inductor for the recharging process. I was suprised, ho easy it was to coil an new inductor (48 and 6 coils) and then also the recharging went again.
    I had also the problem, that after the repair the unit worked only with the half power. But performing a swicht-on / switch-off process of the ramp function (press the button 5 seconds with the unit in the cradle) restored the full power brushing without the ramp.
    @ Jeremy: Perhaps you will try it againg with the unit in the plugged in cradle?
    Regards from Germany

  19. Jon Says:

    I used 2600mAh NimH batteries as well, they worked great.
    To cut the Sonicare 4100 open I used a thin blade miter saw along the length, although I almost cut through the charging coil wires at the base end.
    I had the same problem Jeremy had above after I put the Sonicare back together, even after following the ramp up function instructions using the base.
    After a while, I decided to figure out why it wasn’t working correctly. After looking very carefully at one of the two coils near the the toothbrush end (the “motor”), I noticed one of the thin wires snapped or disconnected at the solder joint. It could have happened when I pried apart the two halves of the Sonicare while cutting it open, or earlier during normal use.
    I sanded the thin wire, twisted it together with another thin wire using a needle nose pliers, and then soldered them together and then to the same termination solder joint. It was a little tough to do since the wire is under the circuit board and I couldn’t unravel any more wire.
    After that fix it works with full power, just like new!

  20. Stewangerne Says:

    OK, let me repeat that… Do you approve of my nice focus Nice joke! How does Michael Jackson pick his nose? From a catalog.

  21. Adam in St. Paul Says:

    I would just like to say thanks to Matthew and to all of the other posters on here for the helpful info. This has no doubt saved me AT LEAST $100. If I come across a way to make this process a little less painful, I will let you know.

  22. stress_guy_53-30 Says:

    I found a guy on eBay who fixed mine in less than a week for $25. Works like new. Look for “Sonic Repair”. I had three old brush heads that wouldn’t fit the new handles, so I took a chance. Glad I did.

  23. John Says:

    Many people used different forms of toothbrushes. Did you know Indian medicine (Ayurveda) has used the neem tree (a.k.a. daatun) and its products to create toothbrushes and similar products for millennia? :)

  24. john Says:

    First of all, Sonicare does not clean as thoroughly as Braun’s Oral-B. When I read Consumer Reports back in the 1980’s, they rated the Oral-B higher than the Sonicare. I moved and changed dentists. My new dentist recommended the Sonicare which I bought. I made the mistake of taking his stupid, ignorant opinion. He probably never tried both brushes. He endorsed Sonicare for the kickback money.

    I stopped using the Oral-B. But when the Sonicare stopped working in two or thress years I returned to the Oral-B. I found by rocking the brush parallel to the horizontal plane that cleaning between the teeth was deeper. I’ve been using the “Oral-B FlossAction replacement electric toothbrush head” for over five years, but with light pressure since too much pressure will cut the tissue. I don’t need a pressure monitor.

    I’ve observed that most if not all German made products I’ve purchased are of high quality. German suspenders last forever. The elastic stetches out before the suspender grips break, which is never.

    By the way, I’m of the experience and opinion that there is no evil in the world but only those angry, abused and/or unsupported individuals that become
    abusers instead of healers. Hitler’s birth mother had four babies of which she lost three. The only survivor was little Adolf. She neglected her husband just a
    wee bit since she did not want to loose her only surviving baby, little Adolf. Consequently, both little Adolf and his mother were abused by his father, her
    husband in the 1890’s.

    Later in his teen years Hitler’s father wanted Adolf to become a civil servant. “But in the grand scheme of things, as young Adolf saw it, the idea of a career
    spent sitting in an office all day long doing the boring paperwork of a civil servant was utterly horrible. The dream of becoming an artist seemed to be the answer to all his present day problems. But his stubborn father refused to listen. And so a bitter struggle began between father and son.

    Hitler began his second year at the high school as the oldest boy in his class since he had been kept back. This gave him the advantage over the other boys.
    Once again he became a little ringleader and even led the boys in after school games of cowboys and Indians, becoming Old Shatterhand. He managed to get better grades in his second year, but still failed mathematics.”

    All reading my musings, please give your children the space and support to follow and determine their own innate futures. When an individual finds and works with their innate abilities, the work is rewarding and alive. Rewarding more in the process and not in the end result. When I found my innate ability I was able to work double shifts without tiring. Work is no longer work!

    If Adolf had been supported and allowed to follow his own innate abilities, imagine the beauty that might have resulted.

    The mortgage scandal and abuse were committed by the so called experts: the bank and financial presidents, CEO’s and directors that clearly knew decades ago that many mortgages would go into foreclosure with home owners loosing their homes.

    All these experts including chairman Alan Greenspan should be sent to prison for their failure to perform their duties. President Obama is another manipulating millionaire that should have froze all mortgage
    foreclosures on his first day as the President. No damn excuse! Send them to the regular prisons, not the resort prisons for white collar crime.

  25. johns number 1 fan Says:

    Thanks for the jaugh John

  26. paul Says:

    You don’t have to buy a new one.
    Better to buy a normal brush and use it more effectively?
    My hygienist recommended i ditch the electric and brush properly by hand.

  27. Jeff in Reno Says:

    I have successfully replaced batteries in 2 Sonicare Advance handles so far. If you are interested, here is how I did it:

    I used an exacto knife and gently score deeper and deeper around the whole joint of the handle until the blade can poke through slightly. Follow the same blade track with every pass. Be very careful around the base as the charging coil wire is right under the plastic. Use your finger tip pressed against the knife blade side to limit downward travel. Then perform one final score and the halves should split apart with no problem using a strong knife blade.

    Carefully remove the circuit board using solder wick or a solder sucker, at the 6 attachments. NOTE: Let the board cool between desoldering each of the 4 top leads to prevent the separation of the copper circuitry from the board itself. Clip the leads to the old batteries, leaving as much of the lead attached to the board as possible. I have found that the easiest way to remove the old batteries from their epoxy bed is, using a long regular tip screwdriver, insert the tip of the screwdriver as far as possible between the batteries and the plastic bulkhead under the top vibrator coil. Gently pry the batteries up and out by pulling the handle toward the top of the handle. Keep the fulcrum of the screwdriver lever over the middle of the bulkhead to avoid damage.

    When replacing the batteries, hard wire the positive and negative free ends together using solderable tin tape. Solder 8mm of tin tape to the other ends of each battery as well to solder to the clipped battery leads. The positive pole is the left top looking down at the opened handle.

    When replacing the circuit board, make sure that the six attachment ports are free of solder. If necessary, use the soldering gun and solder wick to clean these out before trying to position the circuit board back into position. Once in place, heat and solder these joints and then solder the tin battery leads to the clipped battery wires. If the batteries are low in charge, the LED will rapidly blink.

    Temporarily replace the top of the case and place on the charger. The LED should blink once a second if charging correctly. Reglue the case together using a glue like Seal-All.

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