To install the batteries, I would like to give the following tips: 1. A good guide is in Youtube available (Entering Oral B ranges). 2. There are for the Oral-B toothbrush two types of batteries of different sizes, depending on the series. It makes sense before ordering to open the toothbrush and to measure the length of the battery; This ensures that the ordered with the correct dimensions. 3. For desoldering one should have a suction pump and / or solder wick. Some knowledge in soldering of electronic components is also advantageous. With a little patience and tact you can change the battery well now. After changing the batteries, our two toothbrushes running again pretty neat - and it remains the joy of having been mugged by Brown in his outrageous sales policy
