The battery in your Braun Oral-B Series 3000 power toothbrush is rechargeable. However, rechargeable batteries sometimes lose the ability to hold a charge. Should you need to replace the battery for some reason, you can do it in less than an hour with a few simple tools, although Braun advises against it. The task seems daunting, but with concentration and a steady hand, you can remove the old battery and insert a new one.
Open the toothbrush by twisting the bottom counterclockwise 45 degrees.
Pull the inner workings of the toothbrush out of the housing. Place the housing to the side.
Note the two wires inside. Remember where the wires go and how they connect. You will reconnect them later in the process. Remove the wires using the soldering iron.
Loosen the bottom by pushing the attached clip. Make sure you are holding the toothbrush upright to the coil does not come off of the bottom section. Place this bottom section to the side, paying special attention not to dislocate the coil.
Paying attention to the position of the circuit board, remove it to access the battery inside. Use the soldering iron to unfasten both ends of the circuit board in order to remove it.
Slide the battery out of the bottom of the toothbrush.
Use a razor blade to slice open the plastic cover to reveal the two batteries inside.
Put the old plastic cover around the two new batteries to protect them. Do not seal the battery cover; you will need to peek inside to determine which end of the battery is positive and which is negative.
Insert the new battery into the toothbrush, positive end first.
Reattach the circuit board, using the soldering iron to attach both ends.
Replace the bottom part of the toothbrush, lining up the notch at the bottom with the circuit board.
Solder the two wires back into their original positions.
Slide the inner workings containing the battery and circuit board back into the housing and twist the bottom to lock it in place.