Yep, that’s it. There are no contacts and the thing is entirely sealed. How does the charger work?
WAG: Induction. The charger is made to electromagnetically induce a current in the base of the toothbrush, and that current is used to charge a battery somehows.
Yep, TonyF has it. I’ve seen the same mechanism used in other rechargeable products, as well. There’s an iron-core coil in the base and a similar coil in the unit to be charged. The two coils are magnetically coupled, just like the windings in a transformer.
Interesting. I figured it was some sort of magnetic system but didn’t think it was that simple. Is it safe to say that for most items, such as my shaver and toothbrush, that the systems are the same and can be use interchangebly to safely charge them? I tried placing my shaver in the sonicare base and the charge light came on strong. Hard to tell if its getting the right charge or what though.
No. You shouldn’t try to swap parts of different systems. It could damage or destroy them. Think of plugging a 110V appliance into a 220V outlet.
It’s probably not quite that bad, since the coupling constant is fairly low–the windings are not in the same magnetic circuit, except via the low permittivity of the air. Nevertheless, I agree, it’s probably not advisable to try to swap devices if for no other reason than the charging conditions probably would not be optimal, potentially resulting in a permanent loss of battery capacity in the worst case.