Battery problem in Braun electric toothbrush 3D D 15511

In theory yes, in practice...that depends. I have a similar model that failed and I opened it up to see if I could just replace the battery, The problem was everything was corroded to near death inside. The battery is not designed for easy replacement and everything is soldered in place. I found the defective components and was able to order them (IC's & Battery) but the logic board was in very bad shape.

So I would certainly try, otherwise the tooth brush will just end up in the trash. Hopefully you'll have better luck than I did.