Your toothbrush may be dead for reasons other than the battery
This is the correct battery for my Waterpik SR 3000 electric toothbrush, so when it died I assumed that replacing the battery was the smart move.  I've been soldering small electronics since 1968, and I correctly soldered the leads from the device to these very small tabs (much smaller than picture would suggest).  I put the toothbrush on its charging stand and its flashing lights indicated it was charging.  24 hours later, the button on the device was still nonresponsive.  Battery replacement is not a sure thing.
Rating: 3 stars