I have a few-years-old Sonicare toothbrush (not sure what model). It has the Quadpacer feature. Recently the amount of charge it holds has been getting lower and lower. Finally this week it just won't turn on anymore. I've left it charging for days. I'm guessing there are dead rechargeable batteries inside that I could replace for a few $. Then I could probably get a few more years of use.

It frosts me that a company produces a product with lifetime-limited rechargeable batteries and no way to replace them. I've found only one posting on the web on this topic, indicating that it uses AA NiCads.

What is the best way to open the handle case?
What is the best way to reseal the case when you're done?
How well does it work afterward?

Thanks in advance.