It normally takes two to three hours to charge a Aibo battery. Once the battery has a full charge, your Aibo should run for one to two hours depending on how active your Aibo is and how old the battery is. If the run time is less than one hour it’s time to consider having the battery repacked.
If you notice the orange light on his chest starts blinking that will indicate of one of three things:
1. The light starts blinking after about 10 seconds of steady orange, then the battery is either bad or the cell voltage has slipped below the minimum voltage the charge will allow.
2. If the blinking starts after hours of charge, then the series cells are unbalanced and the charging stops short of full charge. In this case go ahead and use the battery and maybe the cells will even out in a few cycles.
3. The light starts blinking after 30 minutes or more, the charger is actually trying to equalize the cells. That means balancing the cell to the same voltage. This may take some hours to work out. If you wait long enough it will go to green.