Battery charger and control method therefor

A battery charger in which charge state data stored in a memory of a battery pack attached to the battery charger and representing a charge state of the battery pack is rewritten in accordance with at least one of a charge current and a charge voltage applied to the battery pack, comprising:

• a determining unit adapted to read out the charge state data stored in the memory of the battery pack and determine whether or not the read out charge state data coincides with current charge state data;
• a full charge capacity data correcting unit adapted to correct full charge capacity data in accordance with a difference between the read out charge state data and the current charge state data when it is determined by said determining unit that the read out charge state data does not coincide with the current charge state data;
• and
• a writing unit adapted to write the corrected full charge capacity data into the memory of the battery pack.

A control method for a battery charger in which charge state data stored in a memory of a battery pack attached to the battery charger and representing a charge state of the battery pack is rewritten in accordance with at least one of a charge current and a charge voltage applied to the battery pack, comprising the steps of:

• (a) counting number of times the charge state data has been rewritten;
• (b) calculating number of charge cycles based on the number of times the charge state data has been rewritten counted in said step (a);
• (c) correcting full charge capacity data based on the number of charge cycles calculated in said step (b);
• and
• (d) writing the full charge capacity data corrected in said step (c) into the memory of the battery pack.

A control method for a battery charger in which charge state data stored in a memory of a battery pack attached to the battery charger and representing a charge state of the battery pack is rewritten in accordance with at least one of a charge current and a charge voltage applied to the battery pack, comprising the steps of:

• (a) reading out the charge state data stored in the memory of the battery pack;
• (b) determining whether or not the charge state data read out in said step (a) coincides with current charge state data;
• (c) correcting full charge capacity data in accordance with a difference between the charge state data read out in said step (b) and the current charge state data when it is determined in said step (b) that the read out charge state data does not coincide with the current charge state data;
• and
• (d) writing the full charge capacity data corrected in said step (c) into the memory of the battery pack.