As 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
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.
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November 6th, 2006 at 12:42 pm
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
951-926-4194
March 11th, 2007 at 10:06 pm
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.
May 14th, 2007 at 5:19 pm
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!
Joe
May 26th, 2007 at 3:56 pm
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.
Thanks,
Gerard
December 5th, 2007 at 5:12 am
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!!!
December 15th, 2007 at 3:41 pm
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.
February 3rd, 2008 at 6:43 pm
so what batteries do you buy to put in there?
February 4th, 2008 at 8:02 pm
James, I believe they are NiCad AA batteries.
February 20th, 2008 at 5:46 pm
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.
March 16th, 2008 at 12:45 pm
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.
April 17th, 2008 at 4:48 pm
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!
June 13th, 2008 at 6:25 pm
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.
July 5th, 2008 at 12:17 pm
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.
August 9th, 2008 at 6:33 pm
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.
August 10th, 2008 at 9:59 am
Thanks for the NiMH info, Greg! The extra run time must be great for those long vacations…
August 12th, 2008 at 3:23 pm
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?
August 12th, 2008 at 3:24 pm
I used a Permatex 2-part epoxy to seal the unit back up. You can’t even tell it was ever pulled apart now.
September 7th, 2008 at 2:04 pm
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
Andreas
October 14th, 2008 at 3:33 am
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!
Peace,
Jon
October 29th, 2008 at 7:42 pm
OK, let me repeat that… Do you approve of my nice focus Nice joke! How does Michael Jackson pick his nose? From a catalog.
November 12th, 2008 at 5:09 am
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.