This is the third one of these I've ended up doing now, and the only one that did not go successfully. For reference, the insides of it look similar to what is shown in this video. After I installed the battery, the brush roared to life, but it seems to not charge up completely or properly somehow. I've yet to measure voltage on the battery, (will try to do that next weekend) but the pitch of the motor is slow enough that I don't think that the actual charging mechanism is working properly. When placed into the charging dock, it lights up and seems to recognize it, and eventually finishes its...