I’m not really sure where to post this, but wanted to share that screwing a 1/4-20 bolt into the bottom hole of my otherwise-sealed Philips Sonicare 4100 and just pulling on it successfully opens the toothbrush. An M6 screw might work too; M5 is slightly too small. Philips says to use a hammer to open it, which is absurd. The battery is still soldered, but in my case that wasn’t what I needed to repair anyway.
Apparently other brands are designed to have replaceable batteries. Don’t buy Philips Sonicare.
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How long did your battery last?
I bought a Sonicare around 15 years ago, and it’s still on its first battery and working fine.
I was planning to do what you did to replace the battery when it finally goes, but I still get about a week’s charge on the current one.
I just checked; mine has a screw in the hole, and looks like it’s designed to come apart.
So I guess they aren’t all the same.
Correct: newer models have no screw.
Most are sealed now so that they are waterproof for use in the shower.
The whole reason I had to open mine up is that water got inside, and I don’t even use it in the shower. I think they removed the screw to either cut costs or make it more difficult to repair.
My first one lasted 11 years. Can’t complain.
My previous one (an older model, which had a screw in the bottom) lasted a long time. This newer “sealed” one got water inside within 2-3 years and had no screw. Fortunately it seems that opening it up and cleaning the circuit board helped.
I tried to take one of these apart to replace the battery and … sadly they did an excellent job of keeping that from happening.
The models with the oval bottom just have that cap pressed into the end with two small clips on the long side of the oval. Deforming the oval into a circle and using a small flat blade screwdriver to pry it out is usually all it takes.
I’ve successfully desoldered the battery for recharging before. We had one go so completely flat the wireless charging wouldn’t work. Putting the battery in an external charger brought it back to life. It was in service for another couple years till a drop in the brush end ruined it.
