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.
Any good alternatives? Sonicair toothbrushes are simply excellent. I only brush once a day because I’m lazy, and my hygienist compliments the lack of plaque and how good my gums are.
I disassembled my old one after it broke when I dropped it. I used the hammer method and was able to put it back together. Newer models are different, so no guarantee.
My 4100 is a “newer” model and I’m happy to report that it was openable by screwing a bolt into the charging hole. But annoyed to report I had to do that in the first place after <3 years due to water ingress.
My experience is that they are not good anymore.
I made the mistake of replacing mine that was working fine but the battery didn’t last too long after 7 or 8 years (didn’t think to replace the battery) and I had to replace the new model 3 times already in 3 years (under warranty but still). I’m noticing more plaque build up too, which never happened with my previous model
I’m waiting to finish my stockpile of replacement heads and I’ll try oral B or whatever else Costco has that is not Phillips