To provide a method of controlling charge and discharge of a secondary
battery for automatic guided vehicle that can decide the timing of
refresh charge and discharge accurately and minimize the frequency of
refresh charge and discharge. The method of controlling charge and
discharge of a secondary battery for automatic guided vehicle comprises a
first discharge step of making the secondary battery drive an automatic
guided vehicle and discharge electricity with a predetermined amount; a
voltage measurement step of measuring a discharge end voltage of the
secondary battery at the completion of the first discharge step; and a
charge step of performing a first charge step of charging the secondary
battery incompletely at a first charging current value when the discharge
end voltage is higher than a preset minimum voltage, and performing a
second charge step of discharging the secondary battery fully and then
charging the secondary battery fully at a second charging current value
smaller than the first charging current value when the discharge end
voltage equals the preset minimum voltage or less.