To enable a user to more accurately know a battery residual quantity of an electronic key, in an electronic key system.
An in-vehicle unit 3 calculates an operation time of a battery from a difference between a battery exchange time from a battery exchange time storage section 35g and the present time from a timepiece section 35f, and calculates a battery residual quantity from the operation time of the battery. A current consumption total sum is calculated from operation information which is updated each time an electronic key 2 is operated, current consumption for each section stored in a current consumption information storage section 35c, and the operation time. The in-vehicle unit 3 calculates the battery residual quantity from a difference between the current consumption total sum and initial power stored in an initial power storage section 35b. An accurate battery residual quantity is calculated while taking into account the calculated battery residual quantity and the battery residual quantity in accordance with the operation time of the battery.
KAWAI HIDEKI
NAGASAKA CHIKAO
| JP2009215826A | 2009-09-24 | |||
| JP2011108166A | 2011-06-02 | |||
| JP2008284855A | 2008-11-27 |
Makoto Onda