| 摘要 |
PURPOSE: To suppress the influence of charging current variation by detecting current and voltage of a storage battery every specified time, finding internal resistance value from the variation of detected values, and making full charging when the internal resistance value obtained exceeds a threshold. CONSTITUTION: Current from a solar cell 4 to a storage battery 10 is detected with a current detecting part 20, voltage is detected with a voltage detecting part 20, and ambient temperature of the battery 10 is detected with a temperature detecting part 24, and detected data are sent to an operating part 26 every constant periods. The variation ratios of current and voltage every constant periods are found, and internal resistance value of the battery 10 is calculated from the variation ratios. Temperature correction is conducted with the output of the temperature detecting part 24, and internal resistance value R is obtained. This value and a reference value stored in a memory part 28 are compared with a comparator 30. When the resistance value R is larger than a threshold value, the battery 10 is considered as fully charged, a signal is outputted to a controller 32, a charging circuit is shut off with a switch 14, and a display 16 displays full charging. Thereby, full charging is accurately detected and overcharging is prevented. |
