Charging device and charging method

A charging method for charging a plurality of battery cells, the plurality of battery cells comprising a first battery cell and a second battery cell, each of the first and second battery cells comprising a first electrode and a second electrode, the second electrode of the first battery cell coupling to the first electrode of the second battery cell such that the first and second battery cells couple to each other in series, the first electrode of the first battery cell coupling to a node which couples to a current-dividing unit and a charging circuit, the charging method comprising the steps of:

• utilizing the charging circuit to provide a first charge current for the node;
• utilizing a control circuit to detect the voltages of the first and second battery cells to generate a voltage detection result;
• according to the voltage detection result, utilizing the control circuit to make the current-dividing unit enter a second state from a first state to share the first charge current if the voltage detection result indicates an unbalanced state, wherein the current-dividing unit has a first impedance under the first state and a second impedance which is less than the first impedance under the second state;
• and
• according to the voltage detection result, utilizing the control circuit to make the charging circuit provide a second charge current instead of the first charge current if the voltage detection result indicates an unbalanced fine-tune state and consequently have the current-dividing unit share the second charge current.

A charging device for charging a plurality of battery cells, the plurality of battery cells comprising a first battery cell and a second battery cell, each of the first and second battery cells comprising a first electrode and a second electrode, the second electrode of the first battery cell coupling to the first electrode of the second battery cell such that the first and second battery cells couple to each other in series, the charging device comprising:

• a node coupling to the first electrode of the first battery cell;
• a charging circuit coupling to the node and providing a charge current for the node;
• a current-dividing unit coupling to the node and functioning as an open circuit to block the charge current under a first state and a resistor with finite resistance to share the charge current under a second state;
• and
• a control circuit coupling to the charging circuit, the current-dividing unit and the first and second battery cells and controlling the current-dividing unit to be under the first or second state,
• wherein the current-dividing unit comprises an energy-storage unit which stores the energy of a partial charge current of the first charge current when the current-dividing unit is under the second state and charges the second battery cell after the current-dividing unit returns to the first state from the second state.