This application is a Continuation of International Application No. PCT/EP2015/071952, filed Sep. 24, 2015, which claims the benefit of and priority to German Patent Application No. 10 2014 219 582.9, filed Sep. 26, 2014, the entire disclosures of which are hereby incorporated by reference herein.
This application relates to a method for measuring or testing the performance of accumulators and to an apparatus for carrying out the method.
For measuring accumulators, accumulator cells or accumulator packs, in particular for determining the performance and the energy content or the capacitance at the end of a charging operation or discharging operation and for determining the capacitance degradation, increase in impedance and/or internal resistance during a cyclization, i.e. when charging and discharging continuously to achieve an accelerated ageing of the accumulators, testing methods are employed, in which standardized measurement parameters are applied to the accumulators to be tested and from the respective measurement values characteristic data and profiles are determined, which are characteristic for the performance of the accumulators. As measurement parameters defined currents, voltages, powers, ambient temperatures, load profiles, typification profiles and temperature profiles are used and by means of control and measurement software measurement and load profiles, ageing profiles and degradation profiles are carried out under program control. From the measurement values, in particular from the charging and discharging current, the charging and discharging voltage as well as the temperature, the capacitance or the energy content of the accumulators and, on the basis of cyclization measurements to achieve an accelerated ageing, the capacitance degradation, increase in impedance and increase in internal resistance of the accumulators are determined.
What is disadvantageous in the known testing methods is the considerable amount of time required for determining the performance of individual accumulators. This is disturbing when applying the known testing methods for a selection of accumulators for particular fields of use, but when applying said methods for testing numerous accumulators used in a large storage device such as a battery power plant, this is not acceptable in operation of the large storage device because of the required insulation of the accumulators to be tested.
It is an object of the present application to indicate a method for measuring or testing the performance of accumulators by determining data and/or profiles characteristic for accumulators, which provides for testing a plurality of accumulators with minimum time and measurement expenditure and for measuring the accumulators in operation of a storage battery or battery power plant.
In accordance with the application, this object is solved with features as described herein.
The solution according to the application is to:
But since the accumulator with the lowest capacitance determines both the duration of charging and the duration of discharging of the series-connected accumulators, the remaining ones of the series-connected accumulators are not yet charged completely at the end of the first measurement phase or not yet discharged completely at the end of the third measurement phase. Correspondingly, in a second measurement phase the remaining N−1 accumulators are recharged up to their full charge and a measurement value corresponding to the capacitance of each of the N−1 accumulators is stored. In the fourth measurement phase following the third measurement phase the N−1 accumulators not yet discharged completely each are connected to the load and likewise discharged completely.
The complete charging and discharging of the remaining N−1 accumulators in the second and fourth measurement phases permits two alternative embodiments.
In a first variant, with or without the separation of the series connection of the N−1 accumulators, the accumulators not yet charged completely are individually connected to the power supply unit, recharged up to their respective full charge, and a measurement value corresponding to the capacitance of each of the N−1 accumulators is stored for the further determination of the individual cycle stability of the accumulators.
In the fourth measurement phase, with or without separation of the series connection of the accumulators, the N−1 accumulators not yet discharged completely likewise are individually connected to the load and discharged completely.
In the second measurement phase of the second variant, the remaining N−1 series-connected accumulators are recharged up to their respective capacitance limit and a measurement value corresponding to the capacitance of that accumulator which has reached its capacitance limit is stored, and this accumulator is separated from the series connection of the N−X accumulators, wherein N and X are integers, N>1 and 2<X<N.
In the fourth measurement phase, the series-connected N−1 accumulators not yet discharged completely analogously are connected to the load, discharged completely and the respective completely discharged accumulator is separated from the series connection of the N−X accumulators.
This second variant provides for a further saving of time, as in the second measurement phase, after full charging of the accumulator of the series-connected accumulators with the lowest capacitance, not each of the remaining accumulators is recharged individually up to reaching its capacitance limit, but the remaining accumulators are recharged jointly until the next accumulator reaches its capacitance limit, the respective capacitance value is stored and the remaining accumulators are recharged until reaching their respective capacitance limit and the respective capacitance values associated to the individual accumulators are stored.
In the fourth measurement phase the series-connected accumulators likewise initially are discharged jointly via the load, until the accumulator with the lowest capacitance is discharged completely. The same is removed from the series connection or isolated in terms of circuitry and the remaining accumulators are discharged further, until the next accumulator is discharged completely, etc.
When applying both measurement methods, a measure for the cycle stability of the individual accumulators already is obtained from completely charging and discharging the accumulators for one time in conjunction with corresponding experience values and comparative measurements. By repeatedly charging and discharging the accumulators, the accuracy of the measurements can be increased, ageing and degradation curves of the individual accumulators can be determined, wherein the reduction of time as a result of the series connection of the accumulators is potentiated correspondingly with several charging and discharging operations.
As criterion for reaching the capacitance limit reaching of the end-of-charge voltage is employed and as criterion for the complete discharge of the accumulators the end-of-discharge voltage is employed, wherein as first or second measurement parameters the charging current, the charging voltage, the charging time, the charging power, the charging energy and the temperature of the series-connected accumulators or of each individual accumulator and possibly in addition the ambient temperature are provided, wherein the charging time is required for determining the charge or capacitance in ampere-hours (Ah) and the energy in watt-hours (Wh).
In a fifth measurement phase each of the N accumulators can individually be connected to the power supply unit and load and can be charged and discharged at least once to determine its specific properties such as capacitance, impedance or internal resistance and to record measurement, load, temperature, ageing and/or degradation curves.
From the first or second measurement values the capacitance and the energy content of each individual accumulator is determined, while from the second measurement values individual measurement, load, ageing and/or degradation profiles are created for each individual accumulator under program control by means of a control and measurement software.
A preferred embodiment of the method according to the application consists in that in the first or second measurement phase a preferably programmed, predetermined cyclization and/or load profile is carried out for the accelerated ageing, capacitance degradation, increase in impedance and increase in internal resistance of the series-connected accumulators and/or of each individual accumulator.
An apparatus for carrying out the method is characterized by a holder for accommodating accumulators with different dimensions and a switching device with controllable switches for the series connection of accumulators and connection of the series-connected accumulators to a power supply unit, a load and a measuring device, for separating the series connection and individually connecting each individual accumulator to the power supply unit, the load and the measuring device, wherein the switching device contains at least a number of controllable switching contacts corresponding to the number of accumulators to be measured, with which in the first and third measurement phases the accumulators are connectable in series to the power supply unit, to the load and to the measuring device, and with which after the first measurement phase the series connection can be separated, and in the fourth measurement phase each individual accumulator is connectable to the power supply unit, to the load and to the measuring device.
As load, there is preferably used an electronic load, which is a current sink in which in contrast to loading with a fixed resistor, with which only a particular load current with a particular resistance value can be adjusted, a load current is adjustable in a defined range under electronic control.
For zero-point lowering on charging and discharging of the accumulators, the negative pole of the electronic load is connected with the negative pole of a voltage source whose positive pole is connected to the negative pole of the power supply unit via a Z-diode.
To be able to connect the accumulators to only one power supply unit, one (electronic) load and one measuring device with little apparatus expenditure and space requirement, the switching contacts consist of a relay circuit with a number of relay contacts, which corresponds to twice the number of the accumulators to be connected in series, wherein a first measurement sensor for detecting the first and second measurement values is connected to an electrical contact of a first accumulator, and further measurement sensors are connected to the connections of the electrical contacts of the series-connected accumulators.
To minimize the time expenditure when connecting the accumulators to the measuring device, the charging and measuring contacts of the measurement sensors consist of pressure pin contacts, so that contacting of the accumulators can be effected without screws, clamps or solder connections.
The pressure pin contacts contain a contact surface which has a surface structure formed in the manner of a waffle iron, so that a very good contact is ensured for contacting to transmit even high currents with easy handling. The waffle-iron-like surface structure ensures that oxide layers or dirt deposits also are penetrated for proper contacting.
To minimize the expenditure for measuring devices, the holder includes steplessly adjustable receptacles for accumulators of a particular type of accumulator with different outside dimensions and/or distances of the electrical contacts of the accumulators, whereby the manufacturing expenditure for measuring devices is minimized and an easy handling and correct alignment of the accumulators to be measured and tested in the measuring device is ensured.
Due to the different geometry of the most important types of accumulator, holders for so-called “pouch cells” and for prismatic accumulators or accumulator cells are provided.
A first holder for accumulators formed as pouch cells consists of a box-shaped rack with a base plate, a cover plate and at least one guide plate between the cover plate and the base plate, wherein the cover plate and the at least one guide plate include guide slots for accommodating the pouch cells, wherein the length of the guide slots corresponds to the maximum width of pouch cells.
Preferably, the at least one guide plate is insertable into the space formed between the cover plate and the base plate so as to be rotatable in the plane by 180° such that in the one alignment of the guide plate for accommodating long pouch cells the guide slots arranged in the guide plate are aligned with the guide slots arranged in the cover plate, and in the other alignment of the guide plate for accommodating short pouch cells the guide slots arranged in the guide plate are arranged offset to the guide slots arranged in the cover plate.
The holder according to the application provides for a steplessly variable adjustment for accommodating pouch cells of various outside dimensions, wherein the adjustability is obtained via the guide slots whose length corresponds to the maximum width of commercially available pouch cells. To be able to hold short and long pouch cells, a variably usable and height-adjustable guide plate is provided, on which short pouch cells rest due to the offset of the guide slots of the guide plate with respect to the guide slots of the cover plate, whereas with a flush alignment of the guide slots of cover plate and guide plate long pouch cells come to rest on the base plate.
Electrical contacting for charging and discharging of the pouch cells as well as contacting of the measurement sensors is effected via pressure pin contacts independent of the respective size of the pouch cells, as the contact tabs of the pouch cells each are formed of the same size.
For prismatic accumulators a second holder consists of a carrier plate with receptacles for the prismatic accumulators and steplessly adjustable guide rails for guiding measurement and charging contact carriers which are adjustable parallel to the plane of the electrical contacts of the accumulators, wherein the receptacles for the prismatic accumulators consist of guide bolts and stops whose position on the carrier plate is adaptable to the outside dimensions of the prismatic accumulators.
To provide for measuring accumulators at defined ambient temperatures, the holders are dimensioned such that they can be inserted into a heating cabinet with which the corresponding ambient temperatures can be produced . . .
With reference to exemplary embodiments illustrated in the drawing the idea underlying the application and variants of the method according to the application and of the apparatus for carrying out the application which can be derived therefrom, will be explained in detail.
The power supply unit 1 consists of four rectifiers connected in parallel at the output end for outputting a d.c. voltage to the switching device 5 with charging and discharging powers in the range of e.g. 0 to 15 kW, a charging current in the range from 0 to 200 A, and charging voltages in the range from 0 to 600 V. To apply the required charging currents and charging voltages, the power supply unit 1 can consist of a larger number of rectifiers connected in parallel, which output the maximum charging voltage of 600 V and the maximum charging current of 200 A.
The electronic load 2 designated as variable resistor takes up a load current adjustable in a defined range under electronic control and is dimensioned such that it can take up discharging powers in the range from 0 to 15 kW, discharging currents in the range from 0 to 200 A and discharging voltages in the range from 0 to 600 V. The electronic load 2 can be regulated very quickly and can carry out exact and defined charging and discharging operations at very high currents and small voltages.
The power supply unit 1 and the electronic load 2 are connected with the switching device 5 via a pre-resistor R1.
For zero-point lowering when charging and discharging the accumulators A1-A8, the electronic load 2 is connected with a voltage source 15 whose positive pole is connected with the negative pole of the power supply unit 1 or the negative connecting terminals of the accumulators A1 to A8 via a Z-diode D1 and whose negative pole is connected with the negative pole of the electronic load 2.
In the exemplary embodiment shown in
For measuring or testing the performance of the accumulators A1 to A8, the series-connected accumulators A1 to A8 in a first measurement phase are connected to the power supply unit 1 and the electronic load 2 by closing the relay contacts k1 and k16 with open relay contacts k2 to k15.
Both measurement phases are carried out with an apparatus corresponding to the circuit diagram shown in
The actuation of the relay contacts k1 to k16 as well as the recording of the measurement values detected at the measurement points MP1 to MP8 is effected via the interface 4 to an individually programmed control and measurement software of the computer control unit 3. The interface 4 actuates both the relay contacts of the switching device 5 and the connection of the measurement points MP1 to MP8 with the measuring device 16.
Beside measuring accumulators for determining data and/or profiles characteristic for accumulators, in order to select suitable accumulators for large storage devices or battery power plants, the method according to the application also is usable for determining the state of degradation of battery or accumulator systems, wherein it is assumed that the degradation measurements of accumulator systems generally are based on the formation of an energy balance by taking account of models for the current cell behavior. All models assume that with increasing operating period the state-of-charge measurement is subject to a more or less pronounced drift, so that the capacitance measurement of an accumulator system involves an indefiniteness which greatly increases with time. Therefore, all accumulator systems regularly must approach defined states of charge, for example a full charge, in order to calibrate the determination of the state of charge, wherein for carrying out the calibration the accumulator system employs a fixed operating regime.
For applying the second measuring method, in which the remaining N−1 series-connected accumulators are recharged up to their respective capacitance limit and that accumulator which has reached its capacitance limit is separated from the series connection of the N−X accumulators, or in which the N−1 series-connected accumulators not yet discharged completely are connected to the load, discharged completely, and the accumulator discharged completely is separated from the series connection of the N−X accumulators, additional relay contacts are arranged in the connections of the series-connected accumulators A1 to A8, of which in the segment of the measuring device of
When the accumulator A3 for example is the accumulator of the series-connected accumulators A1 to A8 which has the lowest capacitance, the relay contacts k19 and k20 closed previously for the series connection of the accumulators A1 to A8 are opened after fully charging the accumulator A3 and the relay contacts k4 and k5 are closed. When the accumulator with the lowest capacitance is the accumulator A1 in the measuring device according to
For a better understanding of the inventive method for determining the cycle stability of the accumulators A1-A8 the state of charge of five accumulators A1 to A5 is shown cross-hatched in
In the third measurement phase the accumulator A4 as first one of the series-connected accumulators A1 to A5 likewise would be discharged completely, while the accumulators A1, A2, A3 and A5 still contain residual charges which in the fourth measurement phase would be discharged by individually discharging the accumulators A1, A2, A3 and A5 via the load until completely reaching the state of discharge.
In use of the second variant of the solution according to the application, after reaching the full charge of the accumulator A4 with the lowest capacitance and storage of the corresponding capacitance value, the accumulator A4 would be separated from the series connection of the accumulators A1 to A5, and in the second measurement phase the remaining accumulators A1, A2, A3 and A5 furthermore would be recharged connected in series, until according to the diagram of
When discharging the series-connected accumulators A1 to A5, the accumulator A4 likewise would be discharged first, while the accumulators A1, A2, A3 and A5 still have residual charges which in the fourth measurement phase are discharged further by successively separating the respective accumulator which is discharged completely.
Apparatuses for carrying out the above-described method for measuring or testing accumulators will be explained in detail below with reference to
Due to the different geometrical structures of accumulators or accumulator cells, receptacles or holders adapted for different accumulator types are provided, which enable the measurement of several accumulators or accumulator cells at the same time. In the following Figures two different types of accumulator are referred to, without the application being limited to these receptacles or holders.
Above the cover plate 74 a plate-shaped contact carrier 75 is arranged, which includes a number of contact plates 11 corresponding to the number of parallel guide slots 70, on which charging contacts 9 for charging and discharging the pouch cells 12, 13 and measurement contacts 10 for detecting the measurement signals are arranged separately from each other.
To adapt the charging and measurement contacts 9, 10 to pouch cells 12, 13 of different width, at least one of the two parallel rows of contact plates 11 is shiftably arranged in the guideways in direction of the double arrow A according to
Due to the different length of the pouch cells 12, 13, the holder 7 for accommodating the pouch cells 12, 13 is formed such that not only pouch cells 12, 13 of different width, but also of different length can be accommodated by the holder 7. For this purpose, at least one of the two guide plates 72, 73 is height-adjustable and both guide plates 72, 73 are insertable into the rack of the holder 7 so as to be rotatable in the plane by 180°, wherein as a result of a different distance of the guide slots 70 from the side walls 76, 77 in the one alignment of the guide plates 72, 73 the guide slots 70 of the cover plate 74 and of the guide plates 72, 73 are aligned with each other, while in the other position of the guide plates 72, 73 they are offset against each other. Depending on the length of the pouch cells 12, 13 either the upper guide plate 73 or the lower guide plate 72 or both guide plates is/are rotated by 180°.
For short pouch cells 13—as shown in
The height adjustability of the guide plates 72, 73 provides for an adaptation of the holder 7 to different lengths of short and medium-length pouch cells 13.
To connect the contact carrier 75 with the cover plate 74 and to firmly contact the charging and measurement contacts 9, 10 with the angled contact tabs 120 of the pouch cells 12, 13 according to
In a top view
The charging contacts 9 are connected with the relay contacts k1 to k16 of the switching device 5 according to
The holder 8 is steplessly variably adjustable for prismatic accumulators 14 with different outside dimensions by means of the stops 87, 88, wherein the circuit boards 81 shiftable along the guide rails 82, 83 provide for an adaptation of the charging and measurement contacts 9, 10 to different distances of the positive and negative poles of the prismatic accumulators 14. The electrical contact and the contact with measurement sensors is effected by means of shiftable copper blocks.
Both in the holder 7 for pouch cells 12, 13 corresponding to
Since the measurements were made at an ambient temperature of T=45° C., a quadrupling of the service life end of the measurement cells can be assumed, as proceeding from an ambient temperature of 25° C. each temperature increase by 10° C. approximately corresponds to a doubling of the ageing of an accumulator cell. The curve of the measurements according to
Number | Date | Country | Kind |
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102014219582.9 | Sep 2014 | DE | national |
Number | Date | Country | |
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Parent | PCT/EP2015/071952 | Sep 2015 | US |
Child | 15468790 | US |