Method to Detect Remaining Battery Power in NotePC
Original Publication Date: 2000-Aug-01
Included in the Prior Art Database: 2003-Jun-20
Disclosed is a method to detect remaining battery power in a NotePC. It makes possible to detect low battery power with necessary and sufficient remaining power to hibernate the NotePC. Hibernation is a function that saves all context of running NotePC to its HDD. If the detection of low battery power is too late, the NotePC is shutdown before saving all context and the user loses his/her valuable data. If the detection is too early, the NotePC's availability is decreased. Measurement of battery power is usually done by accumulating charged/discharged electric current. However the efficiency of battery charge/discharge operation changes due to various causes. Especially the efficiency of charge operation can be affected very much by external factors like atmosphere temperature. Hence estimated remaining battery power by electric current accumulation may contain too much errors to detect lower battery power for hibernation. The method proposed in this disclosure uses two battery cells. Cell A and B are connected in parallel during charge operation and consequent discharge operation. A CPU X accumulate the charge/discharge electric current to/from cell A and cell B separately. When the remaining battery power in two cells reaches at a certain threshold T, CPU X disconnects cell B and continues discharge from cell A. The threshold T is determined at the level that the total remaining battery power in cell A and cell B is estimated at least twice as much power as required to complete a hibernation plus possible accumulation errors.