BATTERY PACK MAINTENANCE FOR ELECTRIC VEHICLE
A method and apparatus for repairing or testing a used battery pack from an electric vehicle include removing the battery pack from the vehicle. Battery tests are performed on at least some of the plurality of batteries and battery test results for each of the batteries tested are obtained. A cradle is configured to receive at least two different types of batteries. The cradle includes connectors to electrically couple circuitry of a battery tester to the battery.
The present application is based on and claims the benefit of U.S. provisional patent application Ser. No. 61/351,017, filed Jun. 3, 2010, and the present application is also a Continuation of and claims priority of U.S. patent application Ser. No. 12/894,951, filed Sep. 30, 2010, the content of which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTIONThe present invention relates to electric vehicles of the types which use battery packs for storing electricity. More specifically, the present invention relates to maintenance of such battery packs.
Traditionally, automotive vehicles have used internal combustion engines as their power source. Petroleum as a source of power. However, vehicles which also store energy in batteries are finding widespread use. Such vehicle can provide increased fuel efficiency and can be operated using alternative energy sources.
Some types of electric vehicles are completely powered using electric motors and electricity. Other types of electric vehicles include an internal combustion engine. The internal combustion engine can be used to generate electricity and supplement the power delivered by the electric motor. These types of vehicles are known as “hybrid” electric vehicles.
Operation of an electric vehicle requires a source of electricity. Typically, electric vehicles store electricity in large battery packs which consist of a plurality of batteries. These batteries may be formed by a number of individual cells or may themselves be individual cells depending on the configuration of the battery and battery pack. The packs are large and replacement can be expensive.
SUMMARY OF THE INVENTIONA method and apparatus for repairing or testing a used battery pack from an electric vehicle include removing the battery pack from the vehicle. Battery tests are performed on at least some of the plurality of batteries and battery test results for each of the batteries tested are obtained. A cradle is configured to receive at least two different types of batteries. The cradle includes connectors to electrically couple circuitry of a battery tester to the battery.
As discussed in the background section, battery packs used with electric vehicles are able to store large amounts of energy. The battery packs are large and difficult to work on and test because of the high voltages involved. Further, the battery packs are expensive. In one aspect, the present application recognizes that a single bad battery within the battery pack can reduce the capabilities of the overall battery pack. A bad battery or (batteries) can reduce the amount of energy the battery pack can store, reduce the rate at which the battery pack can be recharged and cause other batteries with in the battery pack to drain prematurely.
In one aspect of the present invention, a battery pack is removed from the electric vehicle whereby maintenance can be performed on it. More specifically, individual batteries of the pack tested. A refurbished battery pack is made by preparing a new set of batteries for use in creating a refurbished battery pack. The new set of batteries is formed from used batteries from previously used battery pack(s) along with one or more additional batteries. The set of batteries used to form the refurbished battery pack are selected such that they have at least one test result which is similar to the others. The refurbished battery pack can then placed in an electric vehicle and be used as a source of power for the vehicle.
The battery pack 102 is a critical component of the electric vehicle 100. Operation of the battery pack 102 will determine the efficiency of the vehicle, the overall range of the vehicle, the rate at which the battery pack 102 can be charged and the rate at which the battery pack 102 can be discharged.
During the lifetime of vehicle 100, the battery pack 102 will degrade with time and use. This degradation may be gradual, or may occur rapidly based upon a failure of a component within the pack 102. When such a failure occurs, or when the pack has degraded sufficiently, the entire battery pack 102 is typically replaced. The battery pack 102 is one of the primary components of electric vehicle 100 and its replacement can be very expensive. In one aspect, the present invention is directed to performing maintenance on battery pack 102. The maintenance can be performed after the battery pack has failed, or prior to the failure of the battery pack.
In one aspect, the invention includes the recognition that the failure, degradation, or impending failure of battery pack 102 may be due to the failing or degrading of one or more of the individual batteries 140 within the pack 102. In such a case, the battery pack 102 can be refurbished or otherwise repaired by identifying the failed, failing, or degraded batteries 140 and replacing them with operable batteries 140. In another aspect, the present invention includes the recognition that the simple replacement of a faulty battery 140 in a battery pack 102 may not provide the optimum configuration for the repaired or refurbished battery pack 102. More specifically, a “new” battery 140 used to replace a “bad” battery 140 within the battery pack 102 will introduce a battery which is not balanced with respect to other batteries 140 in the pack 102. This unbalanced battery 140 may cause further deterioration in the battery pack 102. Thus, in one aspect, the present invention includes selecting batteries 140 which have a similar characteristic or measured parameter for replacing bad batteries 140 within a battery pack 102.
In one aspect, the present invention provides a method and apparatus in which batteries 140 for use in battery packs 102 are sorted and selected for replacement based upon measured parameters. The measured parameters can be selected such that they are in agreement with one another within a desired range. Example parameters include static parameters in which a static property of a battery is measured using a static function as well as dynamic parameters in which a property of a battery is measured using a dynamic function. Example parameters include dynamic parameters such as conductance resistance, admittance, impedance, etc., as well as static equivalents. Load testing based parameters may also be employed. Other example parameters include battery capacitance, battery state of charge, battery voltage, and others.
During operation, device 200 is capable of measuring a parameter of battery 140 through the Kelvin connections 206 and 208. For example, a forcing function can be applied by forcing function 210. Measurement circuitry 212 can monitor the effect of the applied forcing function signal on the battery 140 and responsively provide an output to microprocessor 214. This can be used to measure a dynamic parameter of the battery such as dynamic conductance, etc. The present invention is not limited to this particular testing method and other techniques may also be employed. Further, the testing of battery 140 or group of batteries 140 may be performed using sensors within battery pack 102. In such a configuration, the testing may be performed without disassembling the battery pack 102. Microprocessor 214 can operate in accordance with programming instructions stored in memory 220. Memory 220 can also store information by microprocessor 214. Operation of device 200 can be controlled by user I/O 220 which can comprise, for example, a manual input such as a keyboard and/or an output such as a display. As discussed below in greater detail, measured parameters of battery can be stored in database 222 for subsequent retrieval.
The battery identification 224 can be in accordance with any technique which will provide information which can be used to identify a battery. This may include, for example, a serial number or the like. The identifying information can be created during the refurbishing process, or at some other time, for example, during manufacture of a battery 140 or pack 102. This information may be manually entered into the database 222 using, for example, user I/O 220 shown in
During operation of the system discussed above, any bad batteries 140 within the battery pack 102 are identified by testing and removed from the battery pack. This may require that the battery pack 102 be charged and discharged. Further, remaining batteries 140 in the battery pack 102, as well as any replacement batteries 140, may be charged or discharged such that they are all at the approximately the same state of charge.
The batteries may be tested while remaining in the pack through connections at individual points between multiple batteries. In another example, the batteries are tested by collecting data over an internal databus of vehicle 100 using techniques described in copending application Ser. No. 12/174,894 which is entitled BATTERY TESTER FOR ELECTRIC VEHICLE, filed Jul. 17, 2008. In another example, the entire battery pack 102 may be tested by supplying a known current to the entire pack 102, or a portion of the pack 102. This current may be a DC current, a time varying DC current, a bi-polar current, a uni-polar AC current, etc. While is current is applied, a battery 140 or groups of batteries 140 within the battery pack 102 can be monitored. This monitoring may be through sensors which are internal to the battery pack 102 or through sensors which are separably applied to the battery 102. In another example, individual batteries are removed from the pack and tested.
The present invention includes the recognition that in a high voltage string of batteries, simply replacing one faulty battery 140 with a new battery 140 may not provide an optimal solution in refurbishing the battery pack 102. This is because the replacement battery 140 may be out of balance with the other batteries 140 in the battery pack 102. Thus, it is desirable that the batteries 140 in the battery pack 102 be balanced in such a way that they have a similar capacity, state of charge, voltage, impedance, conductance, or other parameter, depending upon the selection criteria 254.
The particular selection criteria 254 can be selected as desired. For example, the selection criteria 254 can be determined by testing many batteries 140 across many different battery packs 102 and identifying which parameter 226 or parameters 226 will have a detrimental impact if they are “out of balance” with other batteries 140 within a battery pack 102, identifying a range of acceptable values of a particular parameter 226, identifying an interrelationship between multiple parameters 226 and/or identifying a particular physical or electrical configuration of such batteries 140 within a battery pack 102. Using a load test as an example, a group of batteries 140 may be fully charged and then discharged for a period of time at a desired discharged rate. The voltage of the batteries 140 during or following the discharge can be measured. Batteries 140 having a voltage which is within a selected percentage of the voltage of other batteries 140 may be identified for use in a refurbished battery pack 102. This selection process may be applied only to batteries 140 which are used to replace faulty batteries 140 within a battery pack 102, or may be applied to additional batteries 140 within the battery pack 102 including all of the batteries 140 within a particular battery pack 102. Further, the batteries 140 which are used to replace faulty batteries 140 may themselves be retrieved from other battery packs 102 which are in the process of being refurbished or otherwise disassembled. The replacement batteries 140 may also comprise new or otherwise unused batteries 140. The battery 140 discussed herein may comprise an individual cell or may comprise multiple cells or batteries. The battery 140 and/or cells may operate in accordance with any suitable battery technology. The database 222 discussed above may be implemented in any suitable database 222 format. In one configuration, the database 222 may be implemented manually. In another configuration, the database is stored in a memory, for example, a computer memory.
The test circuitry 352 couples to the battery 350 to a removable cable 360. Cable 360 has ends 362 and 364 which plug into the battery cradle 350 and the test circuitry 352, respectively. The battery 140 can be placed into the cradle 350 whereby tests may be performed by the battery 140. Battery 140 is illustrated as including battery terminals 202 and 204 which couple to Kelvin connections 206 and 208 in cradle 350. These may be Kelvin connections or single connections. A midpoint connector 370 is also illustrated which allows a midpoint test connector 372 to connect to one or more connections between cells or groups of cells within the battery 140.
The configuration shown in
In one configuration, the test circuitry 352 receives information regarding the state of charge and/or voltage of batteries within a battery pack. A replacement battery 140 is then connected to the device 200 and the circuitry 352 adjust the state of charge and/or voltage of the replacement battery 140 to more closely match the state of charge and/or the voltage of the other batteries within the pack. As specified above, similar techniques can be used to balance the state of charge for all the batteries within a battery pack. The information regarding the state of charge and/or voltage can be received by the test circuitry by a user I/O 220 or through remote I/O 354. For example, the information may be received from the onboard databus of the vehicle such as OBDII databus, over wireless connection, input by service personnel. The state of charge of the battery may be determined using an approximate relationship between voltage of the battery, and/or current in/out of the battery, and state of charge. Other techniques may be used including measurement of dynamic parameter as discussed above. When charging a battery, the circuitry can be charged using a constant current or can charge in a constant current or constant voltage mode as desired. In such embodiments, the forcing function 210 is configured as a constant current source, a constant voltage source as well as a load including a constant current load.
Preferably, the test circuitry includes a fail safe configuration whereby if a voltage of a battery is out of a predetermined range, such as 2.5 volts to 4.25 volts, the current or voltage applied to the battery 140 may be terminated. As described below in more detail, the test circuitry can selectively couple to individual cells within the battery 140 if appropriate midpoint connections are provided. A power on self test (POST) and/or watchdog timer can be selectively provided within test circuitry 252 in order to improve the reliability of the device. In one configuration, a “start” button is provided on the user I/O 220 which can be used to initiate the charge/discharge cycle. Over voltage, current and temperature protection is preferably provided in order to protect the battery and the test circuitry.
Similarly, hybrid electric vehicles (HEV) include two types of battery packs.
In one aspect, the present invention provides one or more cradle configuration for receiving a battery 140 and coupling the battery 140 to circuitry device 200. The cradle configuration allows coupling process to be at least partially automated thereby reducing the time required by an operator as well as the likelihood of operator error in providing the coupling. The cradle and associated circuitry can be configured to select a desired polarity of the connections to the battery and physically secure the battery for testing, charging, discharging, etc. This also allows a single cradle to be used with more than one battery configuration.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. As discussed above, the step of identifying can be performed based upon various parameters. Some of these parameters can be independently adjusted by the testing device or otherwise, for example voltage or state of charge for a particular battery or cell. Other parameters cannot be changed, for example, conductance, impedance, etc. In preparing a replacement battery pack, the parameters which can be adjusted independently may be changed as desired, for example, by charging or discharging a battery in order to provide a better match with other batteries in the replacement pack. The step of identifying can be configured such that a greater weight can be given to those parameters which cannot be adjusted. In such a configuration, prior to assembling the replacement battery pack, parameters which can be adjusted to more closely match one another can be changed accordingly. Further, an information in a database can be developed that relates a voltage or state of charge to conductance or impedance for a specific type of battery. In such a situation, if the database information indicates that a match will be difficult to obtain following equalization of adjustable parameters, the measurement device and/or method can be configured such that that particular battery will not be used and thereby saving time during the refurbishing process. Typically, a battery will comprise a lithium ion battery; another example technology is a nickel metal hydrate battery. However, the present invention is not limited to these battery configurations and may be implemented with other battery technologies. Typically electrical vehicle batteries will include four cells for battery module while hybrid electric vehicle batteries will include eight cells per battery module. The connections to a cell or battery can be single connections or Kelvin connections.
Claims
1. A method of repairing a used battery pack from an electric vehicle, comprising:
- removing the battery pack from the vehicle, the battery pack comprising a plurality of batteries;
- performing battery tests on at least some of the plurality of batteries, obtaining a battery test result for the batteries tested and storing the battery test results in a database;
- obtaining a plurality of replacement batteries;
- performing battery tests on the plurality of replacement batteries, obtaining a test result the replacement batteries and storing the battery test results in the database;
- retrieving the battery test results from the database; and
- identifying batteries based upon the retrieved battery test results for use in forming a refurbished battery pack.
2. The method of claim 1 wherein the step of identifying batteries comprises applying selection criteria to the battery test results stored in the database.
3. The method of claim 2 wherein the selection criteria is based upon an adjustable parameter of the batteries, the method further including adjusting the adjustable parameter of at least one battery.
4. The method of claim 2 wherein the selection criteria is based upon an adjustable parameter of the batteries, wherein the selection criteria applies a lower weighting function to the adjustable parameter relative to a nonadjustable parameter.
5. The method of claim 2 wherein the selection criteria includes comparing parameters of batteries to each other and identifying parameters which are within a selected range.
6. The method of claim 2 wherein the selection criteria is based upon multiple parameters of the batteries.
7. The method of claim 1 including storing battery identification information in the database which is associated with a test result for a particular battery.
8. The method of claim 1 including implementing the database in a computer memory.
9. The method of claim 1 wherein the battery test comprise applying a forcing function to a battery and observing a result.
10. The method of claim 1 wherein the batteries comprise individual cells.
11. The method of claim 1 wherein the batteries comprise groups of cells.
12. The method of claim 1 wherein performing battery tests on the batteries in the battery pack is performed prior to removing the battery pack from the vehicle.
13. The method of claim 1 wherein performing battery tests on the batteries in the battery pack is performed subsequent to removing the battery pack from the vehicle.
14. The method of claim 1 wherein the replacement batteries are obtained from another battery pack.
15. The method of claim 1 wherein the replacement batteries comprise new batteries.
16. The method of claim 1 including identifying a configuration of batteries for placement in the refurbished battery pack based upon the battery test results.
17. The method of claim 1 including implementing the step of identifying in a computer.
18. The method of claim 1 including placing the battery pack in a cradle which is coupled to battery test circuitry.
19. An apparatus for use in refurbishing a used battery pack from the electric vehicle, comprising:
- battery test circuitry configured to perform battery tests on batteries in the used battery pack;
- a database configured to contain battery identification information and at least one associated battery parameter obtained from the battery test circuitry;
- a selection criteria which identifies batteries for use in creating a refurbished battery pack; and
- a controller configured to retrieve information from the database, apply the selection criteria and responsively provide selection information output which indicates which of the batteries identified in the database are suitable for use in creating a refurbished battery pack.
20. The apparatus of claim 19 wherein the selection criteria includes comparing parameters of batteries to each other and identifying parameters which are within a selected range.
21. The apparatus of claim 18 wherein the selection criteria is based upon an adjustable parameter of the batteries, the controller further configured to adjust the adjustable parameter of at least one battery.
22. The apparatus of claim 20 wherein the selection criteria is based upon an adjustable parameter of the batteries, wherein the selection criteria applies a lower weighting function to an adjustable parameter relative to a nonadjustable parameter.
23. The apparatus of claim 19 wherein the selection criteria is based upon multiple parameters of the batteries.
24. The apparatus of claim 19 wherein the database includes battery identification information associated with a test result for a particular battery.
25. The apparatus of claim 19 wherein the battery test comprises applying a forcing function to a battery and observing a result.
26. The apparatus of claim 19 wherein the batteries comprise individual cells.
27. The apparatus of claim 19 wherein the batteries comprise groups of cells.
28. The apparatus of claim 19 wherein the selection information output includes information identifying a configuration of batteries for placement in the refurbished battery pack based upon the battery test results.
29. The apparatus of claim 19 including a cradle coupled to the battery test circuitry configured to receive a battery and couple the battery to the battery test circuitry.
30. The apparatus of claim 29 including circuitry coupled to the cradle configured to select a polarity of an electrical connection to the battery.
31. An apparatus for testing a battery of a battery pack from an electric vehicle, comprising:
- test circuitry configured to perform a battery test on the battery;
- a cradle configured to receive the battery, the cradle comprising: first and second connectors configured to electrically connect the test circuitry to end connectors of the battery; and a midpoint connector configured to electrically connect the test circuitry to an electrical midpoint between the end connectors.
32. The apparatus of claim 31 wherein the cradle includes a lock mechanism to secure the battery in the cradle.
33. The apparatus of claim 31 wherein the cradle includes a temperature sensor.
34. The apparatus of claim 31 wherein the midpoint connector includes a plurality of electrical connectors configured to couple to a plurality of electrical midpoints between the end connectors of the battery.
35. The apparatus of claim 31 including a second midpoint connector configured to couple to additional midpoint connections between the end connectors of the battery.
36. The apparatus of claim 35 wherein the midpoint connectors are positioned opposite one another.
37. The apparatus of claim 35 wherein the second midpoint connector is carried on a slidable portion.
38. The apparatus of claim 38 including a lock mechanism to secure the slidable portion to a base of the cradle.
39. The apparatus of claim 37 wherein the cradle includes a cover configured to cover the battery.
40. The apparatus of claim 39 wherein the cradle includes a switch actuated by the cover when the cover is in a closed position.
41. The apparatus of claim 31 wherein the test circuitry is configured to measure a dynamic parameter of the battery.
42. The apparatus of claim 31 including polarity switching circuitry configured to selectively switch polarity of the first and second connectors coupled to the test circuitry.
43. The apparatus of claim 34 including polarity switching circuitry configured to switch polarity of the electrical connectors coupled to the electrical midpoints.
44. The apparatus of claim 31 wherein the first and second connectors comprise Kelvin connections.
Type: Application
Filed: Jun 3, 2011
Publication Date: Dec 8, 2011
Inventor: Kevin I. Bertness (Batavia, IL)
Application Number: 13/152,711
International Classification: H01M 10/42 (20060101); G01N 27/416 (20060101);