I've got a pair of Braun 5409 "Series 3" cordless razors that I swap out between charges. I need to replace
the cutter screens every few months, and the batteries every few years. The "power unit" comes out and
opens up to reveal two AAA batteries with contact pins on the end.
Care must be taken when removing and reinstalling the power unit. The contacts can easily touch the wrong
spot on the board and I've had to replace the switching mosfet once already from touching the wrong spot
during reassembly and smoking the mosfet.
Braus says "Disassembling the appliance will destroy it and invalidate the warranty", but they can't do that.
They're legally allowed to say that, but it'll never hold up legally. A manufacturer can only invalidate the
warranty if the user damages the product, and even then they're only allowed to invalidate the warranty on
the part that the user damaged. The warranty for the rest of the product remains intact. So, as long as you're
careful, you can completely ignore any of those "warranty void if removed" stickers. Although by the time
you need to replace the battery, it'll probably already be out of warranty anyway.
