Method for determining a loss of capacity of a battery storage device, apparatus, and computer program product
Various embodiments include a method for ascertaining a mean capacity loss of a battery storage device. The method may include: providing results of a measurement series on the battery storage device taken during a plurality of load cycles, each including a charging and a discharging phase; ascertaining a first and a second discharge capacity of the device using a first and a second calculation rule, wherein each calibration is different for correcting values of the current measurement; and carrying out an optimization process so a calibration of the current measurement is ascertained to achieve the greatest match of the ascertained first discharge capacity and the second discharge capacity.
1 . A method for operating a high-precision coulometry device to ascertain a mean capacity loss of a battery storage device, the method comprising:
applying a plurality of load cycles to the battery storage device;
testing the battery storage device during the plurality of load cycles to measure a current, wherein each of the load cycles includes a charging phase and a discharging phase;
providing a set of results comprising a plurality of values of the measured current;
ascertaining a first discharge capacity and a second discharge capacity of the battery storage device from the set of results using a first calculation rule and a second calculation rule, wherein different calibrations of the current measurement are included in the first calculation rule and the second calculation rule, wherein each calibration is a calculation rule for correcting individual values of the current measurement;
carrying out an optimization process to select a calibration of the current measurement determined to achieve a closest match of the ascertained first discharge capacity and the second discharge capacity; and
using the selected calibration to adjust the coulometry device and thereafter measure a further discharge capacity for a further battery storage device.
2 . The method as claimed in claim 1 , wherein the first discharge capacity for a load cycle is calculated based on a discharge drift for the load cycle and a coulomb efficiency for the load cycle.
3 . The method as claimed in claim 1 , wherein the first discharge capacity for a load cycle is calculated based on a capacity value after the charging phase of the load cycle and a capacity value before said charging phase.
4 . The method as claimed in claim 1 , wherein the second discharge capacity for a load cycle is ascertained based on a first discharge capacity for a further preceding load cycle and a sum of capacity losses of load cycles arranged between the load cycle and the further load cycle.
5 . The method as claimed in claim 1 , wherein, for the calculation and optimization of the calibration, an offset value is used which defines a difference between a raw electrical signal from a measurement and the measured current value at a current of 0 A and a gradient value is used defining a proportionality factor between the two.
6 . The method as claimed in claim 1 , wherein, for the calculation and optimization of the calibration, a curvature factor is used which defines a non-linear, in particular quadratic, relationship between a raw electrical signal from a measurement and the measured current.
7 . The method as claimed in claim 1 , wherein, for the calculation and optimization of the calibration, the relation between a raw electrical signal from a measurement and the measured current is modelled as a partially linear relation with at least three interpolation points.
8 . The method as claimed in claim 1 , wherein charging and discharging of the load cycle takes place between a lower voltage and an upper voltage of the battery storage device.
9 . The method as claimed in claim 1 , in which in each successive load cycle, a constant temperature prevails within the load cycle.
10 . The method as claimed in claim 1 , wherein:
a first charge displacement is ascertained as the difference between a first upper state of charge and a second upper state of charge;
a second charge displacement is determined as the difference between a first lower state of charge and a second lower state of charge; and
a capacity loss is determined from the difference between the first charge displacement and the second charge displacement.
11 . The method as claimed in claim 1 , wherein load cycles are carried out until the capacity loss in two or more successive load cycles is almost constant.
12 . An apparatus comprising:
a memory store for receiving a set of results for a measurement series on a battery storage device with a plurality of load cycles;
wherein the load cycles each comprise a charging phase and a discharging phase and the results of the set of results each comprise a value of a current measurement; and
a computing unit programmed to:
calculate a first discharge capacity and a second discharge capacity of the battery storage device based on the set of results using a first calculation rule and a second calculation rule, wherein different calibrations of the current measurement are included in the first calibration rule and the second calculation rule, wherein each calibration is a calculation rule for correcting individual values of the current measurement;
carrying out an optimization process to select a calibration of the current measurement determined to achieve a closest match of the ascertained first discharge capacity and second discharge capacity;
adjust settings of a high-temperature coulometry device using the selected calibration and operating the device using the adjusted settings.
13 . A non-transitory computer program product storing a set of instructions which can be directly loaded into a memory store of a programmable computing unit, the set of instructions causing a processor of the programmable computing unit to:
obtain a set of results of a measurement series on the battery storage device taken during a plurality of load cycles, wherein each of the load cycles includes a charging phase and a discharging phase and the set of results comprises a plurality of values of a current measurement;
ascertain a first discharge capacity and a second discharge capacity of the battery storage device from the set of results using a first calculation rule and a second calculation rule, wherein different calibrations of the current measurement are included in the first calculation rule and the second calculation rule, wherein each calibration is a calculation rule for correcting individual values of the current measurement;
carry out an optimization process to select a calibration of the current measurement determined to achieve a closest match of the ascertained first discharge capacity and the second discharge capacity; and
adjust settings of a high-temperature coulometry device using the selected calibration and operating the device using the adjusted settings.