WO2011131946A1 - Electric vehicle battery management system - Google Patents
Electric vehicle battery management system Download PDFInfo
- Publication number
- WO2011131946A1 WO2011131946A1 PCT/GB2011/000627 GB2011000627W WO2011131946A1 WO 2011131946 A1 WO2011131946 A1 WO 2011131946A1 GB 2011000627 W GB2011000627 W GB 2011000627W WO 2011131946 A1 WO2011131946 A1 WO 2011131946A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- battery
- management system
- battery management
- traction
- cell
- Prior art date
Links
- 230000008929 regeneration Effects 0.000 claims abstract description 5
- 238000011069 regeneration method Methods 0.000 claims abstract description 5
- 229910001416 lithium ion Inorganic materials 0.000 claims description 21
- 230000003313 weakening effect Effects 0.000 claims description 7
- 239000002253 acid Substances 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 3
- 238000013459 approach Methods 0.000 description 4
- 238000007599 discharging Methods 0.000 description 3
- 230000002950 deficient Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 230000000153 supplemental effect Effects 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L1/00—Supplying electric power to auxiliary equipment of vehicles
- B60L1/02—Supplying electric power to auxiliary equipment of vehicles to electric heating circuits
- B60L1/04—Supplying electric power to auxiliary equipment of vehicles to electric heating circuits fed by the power supply line
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L50/00—Electric propulsion with power supplied within the vehicle
- B60L50/50—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L50/00—Electric propulsion with power supplied within the vehicle
- B60L50/50—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells
- B60L50/60—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells using power supplied by batteries
- B60L50/64—Constructional details of batteries specially adapted for electric vehicles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/12—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries responding to state of charge [SoC]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/12—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries responding to state of charge [SoC]
- B60L58/14—Preventing excessive discharging
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/12—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries responding to state of charge [SoC]
- B60L58/15—Preventing overcharging
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/18—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries of two or more battery modules
- B60L58/22—Balancing the charge of battery modules
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/24—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries for controlling the temperature of batteries
- B60L58/26—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries for controlling the temperature of batteries by cooling
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/7072—Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02T90/10—Technologies relating to charging of electric vehicles
- Y02T90/14—Plug-in electric vehicles
Definitions
- the field of the invention is a battery management system for an electric vehicle, for example an electric vehicle that uses lithium-ion battery packs for traction.
- Li-ion battery packs made up of large numbers of individual Li-ion battery cells.
- Li-ion cells are attractive for electric vehicle traction/propulsion because of their high power-to-weight ratio, far exceeding that of conventional lead-acid batteries.
- Li-ion cells require individual charge control and management: Li-ion cells are highly sensitive to both over-charging and over-discharging; if the voltage of an individual (and cosdy) cell falls below approximately 2.5V, it can be permanendy damaged.
- a battery management system for an electric vehicle includes (a) a traction battery comprising multiple individual cells and (b) a secondary battery providing power for non-traction electric systems in the vehicle.
- the battery management system enables the secondary battery to be used to provide charge to individual cells in the traction battery.
- Non-traction electric systems include one or more of: electric heater, brake lights during regeneration, reverse lights, reverse warning horn, 12v vehicle charging unit, power steering pump output.
- Implementation features include the following:
- the secondary battery is. typically a lead-acid battery or Li-ion battery; the individual cells in the traction battery are typically Li-ion cells.
- the battery management system is operable to enable the secondary battery to support weakening cells in the traction battery that are approaching a voltage threshold, taking them up from that voltage threshold. Specifically, during discharge, the battery management system monitors cells for voltage at a specific current draw and the battery management system then causes the weakest cell to be topped up for a predetermined time using the secondary battery.
- the threshold is a threshold below which the cells would suffer damage, and is approximately 2.5V for a Li-ion cell.
- Figure 1 shows a schematic overview of the invention implemented in a vehicle.
- Figure 2 shows an example of an implementation of the invention.
- Figure 3A-3B show a circuit diagram for one implementadon of the invention.
- Figure 4 shows a schematic overview of one implementation of the invention.
- Figure 5 shows different charge stages for one implementation of the invention.
- Figures 6-10 show an example of a rotor implementing one aspect of the invention.
- the invention relates to a method for battery management system in an electric vehicle.
- a battery management system for a Li-ion traction battery system the basic principles may be applicable to other kinds of rechargeable battery.
- the typical Li-ion vehicle traction battery pack includes individual cells series connected in a pack.
- the invention is at the cutting edge of modern Li-ion battery pack management systems and has the ability to handle even poorly matched series connected cells. It can charge and discharge (at high current) any individual cell, at any time during bulk charge, thus fully charging all cells.
- the battery e.g. lead-acid or Li-ion
- the battery conventionally used in an electric vehicle for providing power for non-traction electric systems (e.g. for power steering and for lights) is used to support those weakening cells in the traction battery that are approaching the 2.5V threshold; by providing charge to these cells, we avoid the problem of prematurely restricting or terminating discharge from the entire battery.
- This significandy improves vehicle range.
- the invention has been tested in one embodiment on a battery pack with a defective cell loaded into the pack and this system has proved to support the defective cell in both charge and discharging whilst driving.
- Figure 2 shows three of the units (Charging module, Vehicle interface module and Battery management system (BMS) module) when installed in a car.
- the system is totally modular, comprising individual waterproofed units in the embodiment shown in Figure 2.
- One implementation of the invention utilizes a switching matrix that allows access to any cell to charge or discharge at any time.
- one embodiment of the invention utilises a system where it is imposable for any two cells to be shorted out.
- One embodiment of this system is shown in Figures 6 to 10, where an electro-mechanical device called a 'rotor' can charge or discharge any cell at anytime without fear of shorting two nodes or cell terminals.
- the invention has a full real-time current sensing system, thus giving the operator accurate battery state indication, including any ancillary drains such as, electric heater, and all other vehicle usage. Active opportunity charge also indicates battery top up in real time.
- the preferred implementation uses a twin battery pack system: (a) the main traction battery and (b) the secondary battery that services the car's normal requirements (electric heater, brake lights during regeneration, reverse lights, reverse warning horn, 12v vehicle charging unit, power steering pump output etc.).
- This secondary battery is used to supply energy to individual (weakening) traction cells as required during traction pack discharge, taking them up from the dangerous 2.5V threshold. This has the effect of supporting any and all cells during the discharge until all traction cells are balanced at their lowest, safe threshold, at which point we have a true, even discharge of the maximum safe extent from the Li-ion traction battery pack— greatly increasing range.
- the main Bulk charger is a high efficiency 240V AC charger that is applied to the traction battery and is throtded by the charge computer and the secondary 240V AC charger is applied to individual cells that are lagging in bulk charge. This is supplied via the rotor and has the effect of all cells being balanced and fully charged.
- Phase one bulk charge with reference to Figure 5.
- Full power is applied by the Bulk charger to the traction pack; the secondary charger is providing supplemental charging to lagging cells via the mechanical rotor (described in detail later).
- Phase two Phase two, with reference to Figure 5.
- the highest cell i.e. cell with the highest voltage
- the main charger is throtded back, for example to 15 Amps and the rotor now bleeds charge off the highest cell to again balance the pack.
- the Bulk charger throtdes to maintain cells at a predefined voltage level, for example 4.2v and the secondary charger sequences through the whole pack, cell by cell, charging or discharging as required to maintain the pack in a full state.
- the computer changes the rotor to top-up mode.
- the lowest cells i.e. with the lowest voltage
- the weakest cell is then topped up for a pre-determined time using the secondary battery. This cycle is continued throughout the discharge cycle.
- the battery discharge indicator read indicates that all of the cells (or a predefined number) have reached a predetermined lower level
- the car then enters a "Get me home mode". The current draw is then limited and low-cell top up cycle time is reduced to get the last bit of energy out of the pack. At no time is any individual cell allowed to drop below critical a critical level, typically 2.5v for U-ion batteries.
- the rotor is described with reference to Figures 6 to 10.
- the rotor includes a rotor body that is powered by a stepper motor - the rotor body can hence move in small steps around a circle.
- Arranged in the circle are multiple pairs of cell contact apertures formed through a thick, electrically insulating sheet; one pair for each cell in the battery traction pack, each aperture sufficiently distant from an adjoining aperture to remove the risk of shorting.
- a cell contact is hard wired to a cell's terminal.
- the rotor body includes a pair of main contacts (cylindrical pins) that can be forced through a pair of cell contact apertures by a pusher plate activated by a solenoid; the main contacts are connected to the terminals of the secondary battery, so that they can connect the terminals of the secondary battery (as well as the secondary mains charger) to the terminals of each cell in the traction pack in succession as the rotor body steps around the circle.
- This is a simple, low-cost and robust mechanical arrangement that allows the secondary battery (as well as the secondary mains charger) to charge and discharge individual cells in the traction battery pack with no risk of incorrect connection or shorting across a cell.
- High current distribution from the secondary pack to the traction pack is prioritised by a set of rules implemented via the master processor and physically via the rotor.
- the software When commanded, the software carries out the following:
- the invention as implemented in the Electric Vehicles Company's "EVC ULTRA RANGE BMS" utilizes three micro computers integrated together to control the battery management duties above with the vehicle control computer commanding the drive system in real time to manage acceleration, deceleration and regenerative braking, giving total vehicle performance levels of over 7 Miles per Kw hour.
- the "EVC ULTRA RANGE BMS" modular approach is designed for ease of maintenance in the field, there are no set ups, all vehicle specific configuration is carried out by software specific download either already in the units as supplied from the factory or with downloads via the internet.
- the "EVC ULTRA RANGE BMS" has been developed to get the maximum range from a very small pack.
- the EVC vehicle conversions have between 8 to 15 Kw hour packs depending on type and constantly exceed 60 miles per charge range for normal driving.
- the Traction unit as shown in Figures 1 and 2 is a three phase AC drive system, this unit is , mounted in close proximity to the AC motor and in one implementation comes ready to install with wiring harness and mounted on its water cooling jacket so as to supply any excess heat to the vehicle heating system, or to heat the traction battery to its optimal 20 degree Celsius operating termperature.
- Heating the traction battery is achieved using a simple pipe that circulates heated water in a heat source placed under the battery; a thermostat is used to ensure that heat is applied when needed (especially important in very low temperatures). By keeping the traction battery close to its optimal temperature, we find that range is not substantially reduced in low ambient temperatures.
- the Vehicle interface module as shown in Figures 1 and 2 controls non-traction electric systems— i.e. vehicle ancillaries such as electric heater, brake lights during regeneration, reverse lights, reverse warning horn, 12v vehicle charging unit, power steering pump output.
- vehicle ancillaries such as electric heater, brake lights during regeneration, reverse lights, reverse warning horn, 12v vehicle charging unit, power steering pump output.
- the Battery management system (BMS) module as shown in Figures 1 and 2 is the main component of the battery management.
- the system processor runs under the guidance of the vehicle processor and controls in one embodiment up to 32 lithium ion cells during all states of bulk charge, top up charge, balancing and driving conditions.
- the unit has the ability to charge or discharge at quite high currents any cell at any time, this to maximise the life of the pack and attain the maximum range from the vehicle.
- the Charging module as shown in Figures 1 and 2 is in one embodiment a highly efficient switch mode bulk charger capable of charging up to 32 lithium ion cells at up to 32 Amps. Input voltage could typically be either 110 vac, or 240 vac.
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Secondary Cells (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
- Electric Propulsion And Braking For Vehicles (AREA)
Abstract
A battery management system for an electric vehicle is disclosed. The vehicle includes (a) a traction battery comprising multiple individual cells and (b) a secondary battery providing power for non-traction electric systems in the vehicle. The battery management system enables the secondary battery to be used to provide charge to individual cells in the traction battery. Non-traction electric systems include one or more of: electric heater, brake lights during regeneration, reverse lights, reverse warning horn, 12v vehicle charging unit, power steering pump output.
Description
ELECTRIC VEHICLE BATTERY MANAGEMENT SYSTEM
BACKGROUND OF THE INVENTION
1. Field of the Invention
The field of the invention is a battery management system for an electric vehicle, for example an electric vehicle that uses lithium-ion battery packs for traction. 2. Technical background
Electric vehicles typically use Li-ion battery packs, made up of large numbers of individual Li-ion battery cells. Li-ion cells are attractive for electric vehicle traction/propulsion because of their high power-to-weight ratio, far exceeding that of conventional lead-acid batteries. However, Li-ion cells require individual charge control and management: Li-ion cells are highly sensitive to both over-charging and over-discharging; if the voltage of an individual (and cosdy) cell falls below approximately 2.5V, it can be permanendy damaged.
This situation is made more complex because there are manufacturing tolerances in each cell, meaning that capacity and impedance vary from cell to cell. Cells also behave differendy depending on there position in the battery pack. Noticeably, cells positioned at either end of a series connected string suffer more charge depletion than those positioned in the centre of the pack. When bulk charging a series connected pack of for instance 32 cells, there will be some cells that arrive at the fully charged threshold whilst other cell will only be 90% charged.
3. Description of the Prior Art
As noted above, you cannot discharge lithium-ion cell below 2.5v or they will be damaged. In a conventional battery management system, as soon as a single cell in a battery pack (which can be made up of 32 or more individual Li-ion cells) approaches this 2.5V threshold, the battery management system places the vehicle into a low speed, 'emergency' mode. Once the weakest cell is even closer to the 2.5V threshold, then no further power is drawn from the entire battery pack at all to ensure that no damage is
done. But in practice, although you have to stop taking energy from the entire pack because the lowest cell has reached its minimum threshold, there could still be perhaps 20% charge remaining in the pack, overall. The range of the vehicle is less than it could be because of this approach to battery power management. On the next cycle, the situation only gets worse as the lowest cell will again not attain full charge and again will be the first cell to force the discharge cycle to have to stop prematurely; vehicle range is hence less than it could or indeed should be.
The situation only gets worst with age. Stronger cells dominate the pack and the weak ones keep terminating the discharge cycle prematurely.
Sophisticated charge control and load balancing systems have been proposed to address these problems, but they are costly and unreliable and frequently require additional costly components; for electric vehicles to become a mass-market solution, then there remains a need for a low-cost, robust solution.
SUMMARY OF THE INVENTION
A battery management system for an electric vehicle is disclosed. The vehicle includes (a) a traction battery comprising multiple individual cells and (b) a secondary battery providing power for non-traction electric systems in the vehicle. The battery management system enables the secondary battery to be used to provide charge to individual cells in the traction battery. Non-traction electric systems include one or more of: electric heater, brake lights during regeneration, reverse lights, reverse warning horn, 12v vehicle charging unit, power steering pump output.
Implementation features include the following:
The secondary battery is. typically a lead-acid battery or Li-ion battery; the individual cells in the traction battery are typically Li-ion cells.
The battery management system is operable to enable the secondary battery to support weakening cells in the traction battery that are approaching a voltage threshold, taking them up from that voltage threshold. Specifically, during discharge, the battery management system monitors cells for voltage at a specific current draw and the battery management system then causes the weakest cell to be topped up for a predetermined time using the secondary battery. The threshold is a threshold below which the cells would suffer damage, and is approximately 2.5V for a Li-ion cell. By providing charge to these weakening cells, the battery management system enables the secondary battery to support any and all cells during the discharge until all cells in the traction battery are balanced at their lowest, safe threshold, hence avoiding the problem of prematurely restricting or terminating discharge from the entire battery.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a schematic overview of the invention implemented in a vehicle. Figure 2 shows an example of an implementation of the invention.
Figure 3A-3B show a circuit diagram for one implementadon of the invention. Figure 4 shows a schematic overview of one implementation of the invention. Figure 5 shows different charge stages for one implementation of the invention. Figures 6-10 show an example of a rotor implementing one aspect of the invention.
DETAILED DESCRIPTION
The invention relates to a method for battery management system in an electric vehicle. Although we will describe a battery management system for a Li-ion traction battery system, the basic principles may be applicable to other kinds of rechargeable battery.
The typical Li-ion vehicle traction battery pack includes individual cells series connected in a pack. The invention is at the cutting edge of modern Li-ion battery pack management systems and has the ability to handle even poorly matched series connected cells. It can charge and discharge (at high current) any individual cell, at any time during bulk charge, thus fully charging all cells.
It also has the ability to support any individual low cell during driving, thus extending the range of the vehicle markedly. Specifically, the battery (e.g. lead-acid or Li-ion) conventionally used in an electric vehicle for providing power for non-traction electric systems (e.g. for power steering and for lights) is used to support those weakening cells in the traction battery that are approaching the 2.5V threshold; by providing charge to these cells, we avoid the problem of prematurely restricting or terminating discharge from the entire battery. This significandy improves vehicle range. The invention has been tested in one embodiment on a battery pack with a defective cell loaded into the pack and this system has proved to support the defective cell in both charge and discharging whilst driving.
One embodiment of the method is schematically described in Figure 1 where the four main units are presented:
• Traction drive unit
• Charging module
• Vehicle interface module
· Battery management system (BMS) module
Figure 2 shows three of the units (Charging module, Vehicle interface module and Battery management system (BMS) module) when installed in a car.
The system is totally modular, comprising individual waterproofed units in the embodiment shown in Figure 2. One implementation of the invention utilizes a switching matrix that allows access to any cell to charge or discharge at any time.
For consistency and reliability of the system one embodiment of the invention utilises a system where it is imposable for any two cells to be shorted out. One embodiment of this system is shown in Figures 6 to 10, where an electro-mechanical device called a 'rotor' can charge or discharge any cell at anytime without fear of shorting two nodes or cell terminals.
In one embodiment, the invention has a full real-time current sensing system, thus giving the operator accurate battery state indication, including any ancillary drains such as, electric heater, and all other vehicle usage. Active opportunity charge also indicates battery top up in real time.
Battery management
The preferred implementation uses a twin battery pack system: (a) the main traction battery and (b) the secondary battery that services the car's normal requirements (electric heater, brake lights during regeneration, reverse lights, reverse warning horn, 12v vehicle charging unit, power steering pump output etc.). This secondary battery is used to supply energy to individual (weakening) traction cells as required during traction pack discharge, taking them up from the dangerous 2.5V threshold. This has the effect of supporting any and all cells during the discharge until all traction cells are balanced at their lowest, safe threshold, at which point we have a true, even discharge of the maximum safe extent from the Li-ion traction battery pack— greatly increasing range. Using the secondary battery in this way is a cheap and effective approach since it has to be present in the vehicle anyway and is readily able to provide appropriate levels of charge to weakening cells in the traction battery.
One aspect of the invention is schematically described in Figure 4 where during charge two AC chargers are used. The main Bulk charger is a high efficiency 240V AC charger that is applied to the traction battery and is throtded by the charge computer and the secondary 240V AC charger is applied to individual cells that are lagging in bulk charge. This is supplied via the rotor and has the effect of all cells being balanced and fully charged.
There are three distinct charging phases, as shown in Figure 5. Phase one, bulk charge with reference to Figure 5. Full power is applied by the Bulk charger to the traction pack; the secondary charger is providing supplemental charging to lagging cells via the mechanical rotor (described in detail later).
Phase two, with reference to Figure 5. When the highest cell (i.e. cell with the highest voltage) reaches a predefined voltage level, for example 3.45v, the main charger is throtded back, for example to 15 Amps and the rotor now bleeds charge off the highest cell to again balance the pack.
Phase three, with reference to Figure 5. The Bulk charger throtdes to maintain cells at a predefined voltage level, for example 4.2v and the secondary charger sequences through the whole pack, cell by cell, charging or discharging as required to maintain the pack in a full state.
Once the pack has been fully charged, it is maintained in phase three until the pack is ready to be discharged.
As soon as current is drawn from the battery pack on discharge, the computer changes the rotor to top-up mode. Then, typically, the lowest cells (i.e. with the lowest voltage) are then monitored for voltage at a specific current draw and the weakest cell is then topped up for a pre-determined time using the secondary battery. This cycle is continued throughout the discharge cycle.
Once the battery discharge indicator read indicates that all of the cells (or a predefined number) have reached a predetermined lower level, the car then enters a "Get me home mode". The current draw is then limited and low-cell top up cycle time is reduced to get the last bit of energy out of the pack. At no time is any individual cell allowed to drop below critical a critical level, typically 2.5v for U-ion batteries.
Rotor system
The rotor is described with reference to Figures 6 to 10. The rotor includes a rotor body that is powered by a stepper motor - the rotor body can hence move in small steps around a circle. Arranged in the circle are multiple pairs of cell contact apertures formed through a thick, electrically insulating sheet; one pair for each cell in the battery traction pack, each aperture sufficiently distant from an adjoining aperture to remove the risk of shorting. At the rear face of each cell contact aperture, a cell contact is hard wired to a cell's terminal. The rotor body includes a pair of main contacts (cylindrical pins) that can be forced through a pair of cell contact apertures by a pusher plate activated by a solenoid; the main contacts are connected to the terminals of the secondary battery, so that they can connect the terminals of the secondary battery (as well as the secondary mains charger) to the terminals of each cell in the traction pack in succession as the rotor body steps around the circle. This is a simple, low-cost and robust mechanical arrangement that allows the secondary battery (as well as the secondary mains charger) to charge and discharge individual cells in the traction battery pack with no risk of incorrect connection or shorting across a cell.
High current distribution from the secondary pack to the traction pack is prioritised by a set of rules implemented via the master processor and physically via the rotor. When commanded, the software carries out the following:
1) Rotates the rotor a step at a time, until the reset switch is made. This occurs initially on switch-on and then every 15 minutes, for rotational accuracy.
2) Rotates the rotor until the two plus and minus contacts in the rotor line up with the cell requiring energy transfer.
3) The master solenoid is then fired bringing the main contacts into contact with the cell contacts.
4) A set of change over switches is now activated for Top up or Bleed setting depending on which way energy has to be transferred.
5) At this point the main transfer switches are closed, transferring energy to or from the cell via the flexible current harness connecting the rotor contacts to the DC to DC converter in the vehicle specific switching unit.
Because of the spacing between cell contacts, it is physically impossible for any contacts to be made incorrectly or cells shorted out. The above described rotor works well for batteries with 32 cells. For batteries with more cells, e.g. 64 cells, linear shuttle arrangement instead of a rotor is desirable because a rotor arrangement would be. too large to be practical. The linear shutde operates in exactly the same manner as the rotor, as described above.
EVC Ultra range BMS
The invention as implemented in the Electric Vehicles Company's "EVC ULTRA RANGE BMS" utilizes three micro computers integrated together to control the battery management duties above with the vehicle control computer commanding the drive system in real time to manage acceleration, deceleration and regenerative braking, giving total vehicle performance levels of over 7 Miles per Kw hour.
The "EVC ULTRA RANGE BMS" modular approach is designed for ease of maintenance in the field, there are no set ups, all vehicle specific configuration is carried out by software specific download either already in the units as supplied from the factory or with downloads via the internet.
The "EVC ULTRA RANGE BMS" has been developed to get the maximum range from a very small pack. The EVC vehicle conversions have between 8 to 15 Kw hour packs depending on type and constantly exceed 60 miles per charge range for normal driving.
The Traction unit as shown in Figures 1 and 2 is a three phase AC drive system, this unit is, mounted in close proximity to the AC motor and in one implementation comes ready to install with wiring harness and mounted on its water cooling jacket so as to supply any excess heat to the vehicle heating system, or to heat the traction battery to its optimal 20 degree Celsius operating termperature. Heating the traction battery is achieved using a simple pipe that circulates heated water in a heat source placed under the battery; a thermostat is used to ensure that heat is applied when needed (especially important in very low temperatures). By keeping the traction battery close to its optimal temperature, we find that range is not substantially reduced in low ambient temperatures.
The Vehicle interface module as shown in Figures 1 and 2 controls non-traction electric systems— i.e. vehicle ancillaries such as electric heater, brake lights during regeneration, reverse lights, reverse warning horn, 12v vehicle charging unit, power steering pump output.
The Battery management system (BMS) module as shown in Figures 1 and 2 is the main component of the battery management. The system processor runs under the guidance of the vehicle processor and controls in one embodiment up to 32 lithium ion cells during all states of bulk charge, top up charge, balancing and driving conditions. The unit has the ability to charge or discharge at quite high currents any cell at any time, this to maximise the life of the pack and attain the maximum range from the vehicle. The Charging module as shown in Figures 1 and 2 is in one embodiment a highly efficient switch mode bulk charger capable of charging up to 32 lithium ion cells at up to 32 Amps. Input voltage could typically be either 110 vac, or 240 vac.
Claims
1. A battery management system for an electric vehicle, in which the vehicle includes (a) a traction battery comprising multiple individual cells and (b) a secondary battery providing power for non-traction electric systems in the vehicle;
in which the battery management system enables the secondary battery to be used to provide charge to individual cells in the traction battery.
2. The battery management system of Claim 1, in which the non-traction electric systems include one or more of: vehicle power steering, lights, fan, electric heater, brake lights during regeneration, reverse lights, reverse warning horn, 12v vehicle charging unit.
3. The battery management system of Claim 1 or 2 in which the secondary battery is a lead-acid battery or Li-ion battery.
4. The battery management system of any preceding Claim in which the individual cells in the traction battery are Li-ion cells.
5. The battery management system of any preceding Claim in which the battery management system is operable to enable the secondary battery to support weakening cells in the traction battery that are approaching a voltage threshold, taking them up from that voltage threshold.
6. The battery management system of any preceding Claim in which, during discharge, the battery management system monitors cells for voltage at a specific current draw and the battery management system then causes the weakest cell to be topped up for a pre-determined time using the secondary battery.
7. The battery management system of any preceding Claim 5 or 6 in which the threshold is a threshold below which the cells would suffer damage.
8. The battery management system of Claim 7 in which the threshold is approximately 2.5V for a Li-ion cell.
9. The battery management system of any preceding Claim 5 - 7 in which, by providing charge to these weakening cells, the battery management system enables the secondary battery to support any and all cells during the discharge until all cells in the traction battery are balanced at their lowest, safe threshold, hence avoiding the problem of prematurely restricting or terminating discharge from the entire battery.
10. The battery management system of any preceding Claim in which, once a battery discharge indicator indicates that all of the cells, or a predefined number, have reached a predetermined lower level, the vehicle then enters a limited current draw mode.
11. The battery management system of any preceding Claim in which a mains voltage bulk charger charges the traction pack in normal charging phase and a mains voltage secondary charger unit charges individual cells that are lagging in the charge process.
12. The battery management system of any preceding Claim including an electromechanical rotor used to charge or discharge any cell in the traction battery by connecting the terminals of an individual cell to the terminals of the secondary battery.
13. The battery management system of Claim 12 in which the rotor is used to charge any cell in the traction battery by connecting the terminals of an individual cell to the terminals of the secondary mains charger.
14. The battery management system of Claim 12 or 13 in which the rotor includes a rotor body that is powered by a stepper motor.
15. The battery management system of Claim 4 in which the rotor body can move in small steps around a circle and arranged in the circle are multiple pairs of cell contact apertures formed through a thick, electrically insulating sheet; one pair for each cell in the battery traction pack, each aperture sufficiently distant from an adjoining aperture to remove the risk of shorting.
16. The battery management system of Claim 5 in which, at the rear face of each cell contact aperture, a cell contact is hard wired to a cell and the rotor body includes a pair of main contacts that can be forced through a pair of cell contact apertures in the electrically insulating sheet by a pusher plate activated by a solenoid; the main contacts are connected to the terminals of the secondary battery and, optionally, a mains voltage secondary charger, so that they can connect the terminals of the secondary battery to the terminals of each cell in the traction pack in succession as the rotor body steps around the circle.
17. The battery management system of any preceding Claim 1 - 11 in which a linear shuttle is used to charge or discharge any cell in the traction battery by connecting the terminals of an individual cell to the terminals of the secondary battery.
18. The battery management system of any preceding Claim including a heat source that takes heat from a traction unit powered by the traction battery to warm the traction battery to its optimal operating temperature.
19. The battery management system of Claim 1 including a thermostat to control when heat is supplied to the heat source.
20. An electric vehicle including a battery management system as described preceding Claim.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1006580.3 | 2010-04-20 | ||
GBGB1006580.3A GB201006580D0 (en) | 2010-04-20 | 2010-04-20 | Electric converter |
Publications (1)
Publication Number | Publication Date |
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WO2011131946A1 true WO2011131946A1 (en) | 2011-10-27 |
Family
ID=42245485
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/GB2011/000627 WO2011131946A1 (en) | 2010-04-20 | 2011-04-20 | Electric vehicle battery management system |
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GB (2) | GB201006580D0 (en) |
WO (1) | WO2011131946A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2014160759A3 (en) * | 2013-03-29 | 2015-04-23 | Fca Us Llc | Techniques for enhanced battery pack recharging |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1999032323A1 (en) * | 1997-12-23 | 1999-07-01 | Amerigon, Inc. | Radio frequency energy management system |
WO2004036666A2 (en) * | 2002-10-15 | 2004-04-29 | Chaojiong Zhang | Rotary voltage equalizer |
US20040135544A1 (en) * | 2002-11-25 | 2004-07-15 | Tiax, Llc | System and method for determining and balancing state of charge among series connected electrical energy storage units |
FR2927200A1 (en) * | 2008-02-06 | 2009-08-07 | Valeo Equip Electr Moteur | Energy storage device for motor vehicle, has balancing circuits controlling balancing current and balancing time based on external information independent from cells and information associated to cell, provided by diagnosis system |
US20090267566A1 (en) * | 2008-04-23 | 2009-10-29 | Sanyo Electric Co., Ltd. | Car power source apparatus |
CN101640430A (en) * | 2009-09-07 | 2010-02-03 | 清华大学 | Dynamic balancing device for vehicle power battery |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE10139048A1 (en) * | 2001-08-08 | 2003-02-20 | Bosch Gmbh Robert | Automatic battery cell charge state balancing for vehicle, involves bringing primary battery to ready to charge state, checking if charge state balancing can be carried out, and feeding charging current from secondary battery |
-
2010
- 2010-04-20 GB GBGB1006580.3A patent/GB201006580D0/en not_active Ceased
-
2011
- 2011-04-20 GB GB1106638.8A patent/GB2481670B/en not_active Expired - Fee Related
- 2011-04-20 WO PCT/GB2011/000627 patent/WO2011131946A1/en active Application Filing
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1999032323A1 (en) * | 1997-12-23 | 1999-07-01 | Amerigon, Inc. | Radio frequency energy management system |
WO2004036666A2 (en) * | 2002-10-15 | 2004-04-29 | Chaojiong Zhang | Rotary voltage equalizer |
US20040135544A1 (en) * | 2002-11-25 | 2004-07-15 | Tiax, Llc | System and method for determining and balancing state of charge among series connected electrical energy storage units |
FR2927200A1 (en) * | 2008-02-06 | 2009-08-07 | Valeo Equip Electr Moteur | Energy storage device for motor vehicle, has balancing circuits controlling balancing current and balancing time based on external information independent from cells and information associated to cell, provided by diagnosis system |
US20090267566A1 (en) * | 2008-04-23 | 2009-10-29 | Sanyo Electric Co., Ltd. | Car power source apparatus |
CN101640430A (en) * | 2009-09-07 | 2010-02-03 | 清华大学 | Dynamic balancing device for vehicle power battery |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2014160759A3 (en) * | 2013-03-29 | 2015-04-23 | Fca Us Llc | Techniques for enhanced battery pack recharging |
Also Published As
Publication number | Publication date |
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GB2481670A (en) | 2012-01-04 |
GB201006580D0 (en) | 2010-06-02 |
GB2481670B (en) | 2012-08-29 |
GB201106638D0 (en) | 2011-06-01 |
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