Batteries died. It was a puzzle to disassemble it. It was booby-trapped with fragile self-destructing mechanisms like hair-thin wires ready to snap wrapped around the battery which had welded tabs soldered to wires. Requires surgical delicacy but at the same time lots of force to pry 3 plastic clips simultaneously while pulling off an inner casing using 2 hands on a task that needs 4 hands. Had to buy rechargeable batteries with tabs welded on where the tabs were not oriented in the direction the device was designed for so in one joint I had to put the soldering iron directly on the battery terminal. The battery pair costed 1¼ big macs because tabbed nippleless batteries are not a competitive market and only sold at retail prices. A new toothbrush probably would have had the same price but then I would have been suckering into giving them what they want.
I was able to do the job without breakage and it works. I was lucky the soldering heat did not destroy the costly battery. So I would like to send a very big fuck you to #Philips who tried to force me to buy another toothbrush, which I bought before I started boycotting Philips due to their shavers having the same disrespect for a #rightToRepair.
UPDATE
Just checked my records and see that I paid the equivalent of 4 Big Macs (today’s price) back in Jan. 2015. So the original batteries lasted ~8¾ years. Thus the batteries are indeed cheaper. I chose this model because it supports both 120v & 240v which I think is rare with induction charged toothbrushes.
Making a spot welder
Note that instead of buying batteries with tabs, I could have built a spot welder to put tabs on myself which would mean being able to buy any cheap batteries (which is half tempting because I am a cheap bastard). You basically keep an eye out for microwave ovens that people have trashed and cannabalize the transformer which can then be used to make a spot welder. Maybe I’ll do that next time.
Better toothbrushes
There is a toothbrush that takes normal AA batteries (which I keep at my folks’ house). It obviously avoids the problem of permanent batteries. But it has no charging system so the batteries have to be removed periodically for recharging. The bottom cap is very tight fitting plastic over a rubber o-ring which eventually cracked after so many times opening. If the cap had been metal it would have been the perfect toothbrush. One benefit is that it works worldwide.