Patent Application
20100291427
The present invention relates to electrical power systems in electric vehicles. More specifically, the present invention relates to apparatus for and methods of electric coupling of a plurality of batteries to the electronics in an electric motor vehicle.
For a multitude of reasons, it is advantageous to use electric vehicles having rechargeable batteries rather than vehicles using internal combustion engines. Electric vehicles (EVs) are inherently more efficient, meaning more energy is used in locomotion than lost to heat than in conventional engines. Also, EVs do not exhaust any byproducts. However, the use of electric vehicles presents technical challenges. For example, the batteries in an electric vehicle must be recharged. Some electric vehicles are commercially targeted toward daily, low mileage use. Such vehicles are ideal for urban commuters. The batteries are chosen to provide a charge for approximately 50 miles before recharging is required. In some applications, electric vehicles drive well predetermined routes. Vehicles such as buses, delivery trucks, mail trucks, garbage trucks and the like travel predetermined, well known routes. However, most of these vehicles have one large battery. In the example of a municipal bus, the battery can be as large as 4 cubic meters and weigh two tons, and is extremely costly. Also, because such a large battery takes several hours to recharge, the batteries are recharged for use for an entire day. Batteries for other large EVs, such as garbage trucks, are of a similar size, weight and cost. Furthermore, it is well known that batteries may emit heat while charging and discharging. In such large batteries, it comes extremely difficult to maintain temperature uniformity throughout the volume of the battery. The heat also cannot be vented or otherwise managed since the battery is a large, closed device. As a result, the lifetime of the battery is greatly reduced due to temperature non-uniformity. Furthermore, battery management units on board buses, garbage trucks, and the like, are generally programmed to be biased for operation of the EV over maintenance of the battery. Especially in the case of buses, because they carry passengers, the battery management system will prefer to keep the bus operating even in the event of some stress condition on the battery, such as overvoltage, undervoltage, over heating, or the like. Such systems cause greater damage to the battery and further decrease overall operational life.
Modular battery systems and methods of their use are provided herein. Multiple batteries are able to be coupled to a connection backplane. The batteries are modular, meaning in the broadest sense that they are able to be mechanically and electrically coupled or de-coupled from an EV without disturbing the operation of the EV. The batteries are optimally sized for greatest energy capacity versus size and weight, on the order of 20 kg. Advantageously, an optimum number of batteries is able to be used rather than one large battery that is probably larger, heavier, and costlier than is required for daily commuting or travel along a predetermined route, such as a bus route or a delivery route. An on board controller is able to determine if any of the modular batteries are failing for reasons such as overcurrent or undercurrent, temperature, stress, or any other reason. Therefore, a single malfunctioning battery is able to be at least electrically de-coupled from a power delivery system. The malfunctioning battery is not subjected to further stress for the sake of keeping the EV running, as was a shortcoming in the prior art. The EV is able to remain operational because the battery system is modular, and other batteries are able to power the EV while the malfunctioning battery is replaced. Also, only one 20 kg battery need be replaced, rather than the large, non modular two ton battery described above. As a result, a new modular battery is able to be brought to an EV bus along a route, for example. A malfunctioning battery is easily removed by a serviceperson and a new modular battery is inserted, generally within the time a bus would stop to pick up or let off passengers. Such an operation is not feasible in the prior art. Methods and apparatus to realize these benefits are summarized below.
In one aspect of the invention, a connection backplane in a power delivery system of an EV comprises a plurality of mounting positions, each configured to receive a battery, wherein each mounting position has several coupling means. The several coupling means serve to route power, both high voltage (on the order to power an electric motor) and low voltage (for powering electronics), and communication signals between the battery and the powertrain controller. Preferably, the connection backplane is operable to remove or add a battery during operation of the electric vehicle without impeding the operation. In some embodiments, the mounting positions each comprise a latching mechanism for securing the plurality of batteries to the connection backplane. In some embodiments, the backplane comprises a system ground, which is able to be electrically coupled to the chassis of the EV. In one example, for simplicity of wiring and implementation, the coupling means for routing power in each mounting position is linked to a power bus. Similarly, coupling means for routing communication signals can be linked to a communication bus. In some embodiments, the communications signal comprises a battery status signal, capable of indicating the remaining energy within a battery, or warn of a fault condition such as an overcurrent, undervoltage, or temperature fault. In some embodiments, the battery status signal comprises an indication of the conductivity between a battery and the backplane. Furthermore, the communications signal preferably comprises a battery control signal. For example, the battery control signal comprises a shutdown instruction, which causes a malfunctioning battery to de-couple from the overall power delivery system.
In another aspect of the invention, a method of operating an electric vehicle takes advantage of the backplane described above. The method of operating an electric vehicle comprises determining an amount of energy required to power the electric vehicle for a predetermined route and coupling a appropriate number of batteries to the electric vehicle according to the determined amount of energy. As a result, an EV must only carry enough batteries for a certain trip, optimizing the weight of the EV. Preferably, the method further comprises automatically determining if a battery becomes non functional or sub-optimally functional, for reasons listed above. If so, the battery is de-coupled. In some embodiments, the method also comprises recharging the batteries at the end of the predetermined route. Alternatively, the method calls for recharging the batteries at a charging point along the predetermined route. Still alternatively, malfunctioning or discharged batteries are swapped out at the end of the predetermined route, or along a predetermined route.
In the following description, numerous details are set forth for purposes of explanation. However, one of ordinary skill in the art will realize that the invention can be practiced without the use of these specific details. Thus, the present invention is not intended to be limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and features described herein or with equivalent alternatives. Reference will now be made in detail to implementations of the present invention as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or like parts.
The backplane 103 is also in electrical communication with a powertrain controller 120 via a communication bus 131. In some embodiments, the controller 120 is a microprocessor, micro controller, or the like that has been programmed to run the power delivery system of the EV 100. The communication bus 131 delivers a status signal for each of the batteries 102A-102D. In some embodiments, the batteries 102A-102D spontaneously emit status signals indicating either that they are functioning properly or that they are in a fault condition of some sort, such as overcurrent, overvoltage, undervoltage, or overheating. Alternatively, the controller 120 sends a query to each of the batteries 102A-102D to request a status signal or status update. The controller 120 is able to then determine an action with regard to the battery. If the battery is properly functioning, the controller 120 will instruct to battery to continue operating normally, i.e., discharge current or receive a charge. However, if a battery is exhibiting or indicating a fault condition, the controller 120 is able to electrically de-couple the malfunctioning battery. Similarly, if any of the batteries 102A-102D either do not signal at all or do not respond to a query for status, the controller 120 de-couples such batteries. Advantageously, there are other batteries remaining to deliver power to the inverter 140 and thus to the engine 130. When the malfunctioning battery is de-coupled electrically. As a result, the stressor, such as non uniform heat, that was stressing the battery will cease. Therefore, the malfunctioning battery will suffer no further damage. As a result, what is achieved is a longer service life for the batteries 102A-102D. In some embodiments, the controller 120 indicates the condition or status of the batteries 102A-102D on a display screen 125. The display screen 125 displays the remaining charge of the batteries, their temperatures, and any fault conditions that may exist. In some embodiments, the display screen 125 is integrated with other indicators, such as a speedometer. In some embodiments, the controller 120 has more control over the batteries 102A-102D. For example, the controller 120 routs commands via the communication bus 121 and the backplane 103 signaling which of the batteries 102A-102D provide how much power. If one battery 102B is more discharged than another 102C, the controller 120 signals for more power to be drawn from battery 102C than from another battery 102B at a ratio appropriate to their respective levels of charge. Alternatively, the controller 120 queries the driver of the EV 100 through the display 125 how many more kilometers the driver intends to go. The controller 120 then adjusts power output of each of the batteries 102A-102D based on their respective charge, and the optimum rate of discharge for each battery with respect to the remaining travel distance. In some embodiments, the EV 100 comprises an Electric Vehicle Service Equipment (EVSE) 135. EVSEs are standard electrical charging sockets that users of EV are familiar with. Generally, in geographic areas where most EV drivers have a place to park and charge their EV, it may be advantageous to do so.
The backplane 103 is also able to mechanically and electrically couple a thermal management system 150 to the batteries 102A-102D. The thermal management system 150 is able to receive a temperature reading from a temperature sensor 109 (
The form factors of the coupling member 204, the mounting position 103A, and the sets of contacts 226 and 224 are exemplary and not intended to be limiting. In some embodiments, the form factors are industry standard plug- and receptacle. Alternatively, application specific form factors are designed to suit particular needs. Regardless of the form factor, it is advantageous to secure the battery 102A in place once a successful electrical coupling has occurred. To that end, a latch 230 is provided on the mounting position 103A. The coupling member 204 has a corresponding slit 231 to receive the locking edge of the latch 230. Other alternative latching schemes will be readily apparent to those of ordinary skill having the benefit of this disclosure.
Still referring to
Those of ordinary skill in the art with the benefit of this disclosure will readily appreciate other factors for specific applications that must be considered to accurately forecast the energy required for a route. When the energy is determined, the next step 430 is taken. In a step 430, an appropriate number of modular batteries is determined. The appropriate number of modular batteries is the number of modular batteries required to provide the energy determined in step 420. In some embodiments, the determination of step 430 is made by an on board controller, through an interface similar to the controller 120 and display 125 of
Later, during operation of the EVs, in a step 440, a controller, such as the controller 120 of
The amount of time required make a battery swap is on the order of the amount of time the EV bus must stop so that passengers can embark and disembark. In the step 450, the EV bus continues its route. During continuation of the route, the controller continues to monitor the batteries. As a result, steps 440 and steps 450 occur substantially simultaneously. At the end of the route, all batteries are replaced in a step 460. The discharged batteries are placed in charging environments and fresh batteries are swapped into the EV bus for the next route, and the method returns to step 410 if a new route is planned. If the same route is planned, only the number of batteries is determined, as in step 430.
A person of ordinary skill having the benefit of this disclosure will readily appreciate the benefits. In the broadest sense, a minimal number of batteries is used, thereby minimal weight is added to the EV 100, further enhancing efficiency. Prior art EVs have only one immovable battery, which is generally of a far greater size and weight than required for most daily commutes, especially in urban settings where a daily commute may be as little as 10 km. Referring to
While the invention has been described with reference to numerous specific details, one of ordinary skill in the art will recognize that the invention can be embodied in other specific forms without departing from the spirit and scope of the invention as defined by the appended claims. Thus, one of ordinary skill in the art will understand that the invention is not to be limited by the foregoing illustrative details.
The present application claims priority of U.S. Provisional Pat. App. No. 61/178,645, filed May 15, 2009, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61178645 | May 2009 | US |
