My understanding is that Lithium-Ion batteries must be charged differently than NiCad, or Nickel Metal Hydride. The charge must be pulsed on and off. That is why visially looking at a LI-Ion charger, you will see it blinking. Continous charging can cause overheating and an explosion/fire. Also from having had several Craftsman batteries apart, I noticed that the charge is applied to each battery individually. They are not charged in series as other tytes are.