I've had the DiamondClean for 2 days and let it charge first as recommended. Now the green charging indicator seems a bit strange to me. The first time, after about 18 hours, the LED no longer lit up, so I thought it was charged. Out of curiosity, I lifted it up and plugged it in again, and the charging indicator stayed green for about 5 hours until this morning. Today I did the same, lifted it briefly and plugged it in again, and now it has been lit green again for 2 hours. Am I doing something wrong? Surely the toothbrush is charged when the green indicator is no longer lit?