Storage battery diagnosing system
An ammeter measures current when a storage battery having a plurality of single batteries connected in series is charged or discharged. A voltmeter measures total voltage of the storage battery. A calculation device calculates dV/dt obtained by differentiating the total voltage with respect to time on the basis of a relationship between the total voltage and charging time or discharging time, separates a characteristic peak obtained by a dV/dt curve into peaks for the respective single batteries, and diagnoses soundness of the storage battery on the basis of the separated peaks.
1 . A storage battery diagnosing system comprising:
an ammeter for measuring current when a storage battery having a plurality of single batteries connected in series is charged or discharged;
a voltmeter for measuring total voltage V of the storage battery; and
a calculator which calculates dV/dt obtained by differentiating the total voltage with respect to time t on the basis of a relationship between the total voltage and charging time or discharging time, separates a characteristic peak obtained from a dV/dt curve into peaks for the respective single batteries, and diagnoses soundness of the storage battery on the basis of the separated peaks.
2 . The storage battery diagnosing system according to claim 1 , wherein
the calculator compares medians, intensities, or widths of the peaks separated for the respective single batteries, with those for a brand-new storage battery, in order to diagnose soundness of the storage battery.
3 . The storage battery diagnosing system according to claim 2 , wherein
in a case in which n single batteries are connected in series, n being an integer not less than 2, by using peak shape functions of Expressions 1 to n for the peaks for the respective single batteries, A1 to An which are intensities of the peaks for the respective single batteries, μ1 to un which are medians of the peaks for the respective single batteries, and σ1 to on which are widths of the peaks for the respective single batteries, are set as variables, and collation is performed by a least squares method between Expression m of a sum for the n single batteries and actual measured values of the total voltage in order to obtain an approximation expression, and
the peaks for the respective single batteries are estimated by the approximation expression in order to diagnose soundness of the storage battery,
fcell
1
=
f
(
x
,
A
1
,
μ1
,
σ1
)
Expression
1
⋮
fcelln
=
f
(
x
,
An
,
μ
n
,
σ
n
)
⋯
Expression
n
fbattery
=
fcell
1
+
⋯
+
fcelln
⋯
Expression
m
where x is a variable corresponding to time t.
4 . The storage battery diagnosing system according to claim 3 , wherein
as an index indicating a dispersion degree of the medians, the intensities, or the widths among the single batteries, a standard deviation is used.
5 . The storage battery diagnosing system according to claim 4 , further comprising a display for displaying a diagnosis result, wherein
the standard deviation is compared with a storage battery deterioration determination reference value prepared in advance, and when the standard deviation has become larger than the storage battery deterioration determination reference value, the displayer issues a storage battery deterioration alarm.
6 . The storage battery diagnosing system according to claim 3 , wherein
as an index indicating a dispersion degree of the medians, the intensities, or the widths among the single batteries, a difference between a maximum value and a minimum value of the medians, the intensities, or the widths is used.
7 . The storage battery diagnosing system according to claim 2 , wherein
as an index indicating a dispersion degree of the medians, the intensities, or the widths among the single batteries, a standard deviation is used.
8 . The storage battery diagnosing system according to claim 7 , further comprising a display for displaying a diagnosis result, wherein
the standard deviation is compared with a storage battery deterioration determination reference value prepared in advance, and when the standard deviation has become larger than the storage battery deterioration determination reference value, the display issues a storage battery deterioration alarm.
9 . The storage battery diagnosing system according to claim 2 , wherein
as an index indicating a dispersion degree of the medians, the intensities, or the widths among the single batteries, a difference between a maximum value and a minimum value of the medians, the intensities, or the widths is used.