Voltage measurement method for battery
In a battery cell unit, in which battery cells are connected in series, channels for which the battery cells are divided are sequentially connected to a capacitor, and a channel voltage is measured per the channel. For an abnormal channel whose deviation of the measured channel voltage from a reference voltage is larger than a permissible deviation value, measurement is performed by extending a charging time for charging the capacitor. For a normal channel whose deviation is equal to or smaller than the permissible deviation value, the measurement is performed by shortening the charging time for charging the capacitor so as to maintain a measurement cycle, in which the measurement on all of the channels is performed, to be constant.
1. A voltage measurement method comprising:
sequentially connecting m channels, for which n battery cells are divided, in a battery cell unit, in which then battery cells are connected in series, to a capacitor via a connection circuit and measuring a channel voltage per the channel, m being an integer equal to or smaller than n, and n being an integer equal to or larger than two; and
comparing a deviation of a measured channel voltage from a reference voltage with a permissible deviation value, wherein
for an abnormal channel whose deviation of the measured channel voltage from the reference voltage is larger than the permissible deviation value, measurement is performed by extending a charging time for charging the capacitor, and for a normal channel whose deviation is equal to or smaller than the permissible deviation value, the measurement is performed by shortening the charging time for charging the capacitor so as to maintain a measurement cycle, in which the measurement on all of the channels is performed, to be constant.
2. The voltage measurement method according to claim 1 , wherein
in a case where the abnormal channel exists among the channels on which the measurement is performed in a certain measurement cycle, the charging time during the measurement on the abnormal channel is extended in a next measurement cycle, and the charging time during the measurement on the normal channel is shortened in the next measurement cycle.
3. The voltage measurement method according to claim 1 , wherein
in a case where the channel on which the measurement is performed in a certain measurement cycle is the abnormal channel, the charging time of the abnormal channel is extended to perform remeasurement on the abnormal channel in the same measurement cycle, and the charging time of the normal channel on which the measurement is performed after the abnormal channel is shortened in the same measurement cycle.
4. The voltage measurement method according to claim 1 , wherein
the measurement cycle is divided into two periods of a measurement period in which the measurement on the m channels is performed and a non-measurement period that follows the measurement period, and the measurement period is maintained to be constant.
5. The voltage measurement method according to claim I, wherein
the reference voltage is an average voltage of the channel voltages that are measured from a plurality of the channels.
6. The voltage measurement method according to claim 1 , wherein
when the charging time of the normal channel is shortened, a plurality of the charging times of the normal channels is equally shortened.
7. The voltage measurement method according to claim 1 , wherein
the charging times of all of the channels are set to a reference charging time when voltage measurement in the next measurement cycle is started from a certain measurement cycle.
8. The voltage measurement method according to claim I further comprising
comparing an extended charging time of the abnormal channel with a specified upper limit charging time and determining that the abnormal channel is a malfunctioning channel in a case where the extended charging time exceeds the upper limit charging time.