Method of dynamic speed modulation in extended braking applications in electric vehicles

Abstract

A method of dynamic speed modulation in extended braking applications in a battery-powered electric vehicle is disclosed. The method includes determining a sensed parameter of the battery, and determining a parameter threshold of the battery. If the sensed parameter of the battery is the same or exceeds the parameter threshold, decreasing the groundspeed of the vehicle to a predetermined safe speed. If the sensed parameter of the battery is below the parameter threshold, determining the change in the parameter which would be caused by the regenerative braking system at the current groundspeed of the vehicle. If the change in the parameter would cause the sensed parameter to remain, reach or exceed the parameter threshold, correspondingly decreasing or increasing the groundspeed of the vehicle to cause the sensed parameter to approximate but not exceed the parameter threshold of the battery. A controller and electric vehicle capable of same, are also disclosed.

Description

Method of Dynamic Speed Modulation in Extended Braking Applications in Electric Vehicles Field of the invention:

[0001] This invention is in the field of battery-powered electric vehicles including regenerative braking systems, and more specifically relates to a method and controls for the dynamic speed modulation of such a vehicle in extended braking applications, such as extended downhill running and the like. Background:

[0002] Electric vehicles can use regenerative braking while traveling downhill to maintain a constant speed. There are a number of advantages to this approach, including the reduction or elimination in the consumption of break friction material, as well as the capability for energy to be recovered and stored in the battery pack or module of the vehicle.

[0003] When the battery pack approaches a fully charged state, however, it cannot readily accept additional energy. This results in reduced motor regenerative torque, and the potential for increased vehicle speed, to the point of runaway and loss of control. If there were method of controlling or operating such an electric vehicle as the battery approaches the fully charged state without a reduction in the motor regenerative torque, it is believed that this would be desirable and commercially beneficial.

[0004] The prior art acknowledges the use of kinetic energy from regenerative brakes to charge the power system in an electric vehicle, albeit requiring or encompassing operation of the motors at a diminished torque to reduce overcharging of the battery. A number of attempts have been made to address the potential to overcharge the battery on such an electric vehicle. . One solution to prevent the batteries from reaching full capacity is to simply not charge them to 100%. Another known solution is to incorporate a braking resistor capable of dissipating the full regenerative braking power of the vehicle. However, charging to less than 100% does not address other reasons why the battery should not be accepting a charge, such as its operating temperature or cell resistance. It also can limit the ability of the vehicle to balance the cells to ensure battery health and long term performance. A third solution is to simply stop using generative braking, and instead, rely on friction brakes.

[0005] Where braking resistors are employed, with variations in vehicle speed, vehicle weight and slope grades (for example traveling downhill) it can be possible to exceed the power capacity of the vehicle and its breaking resistor. This presents a productivity and safety issue. Summary of the invention:

[0006] In one aspect of the present invention, there is provided a method of dynamic speed modulation in extended braking applications in a battery-powered electric vehicle, where the electric vehicle comprises: at least one electric motor operatively connected to a drive train of the vehicle; a rechargeable battery for supply of power to the at least one electric motor; a regenerative braking system operatively connected to the at least one electric motor which progressively limits the groundspeed of the vehicle and provides recharging power to the battery; and a controller with control software. The control software is capable of monitoring a sensed parameter of the battery and the current groundspeed of the vehicle; determining a change in the parameter which would be caused by the regenerative braking system at the current groundspeed of the vehicle; and adjusting the current groundspeed of the vehicle between zero and a maximum operating groundspeed.

[0007] During operation of a power system of the vehicle, the method comprising using the controller to continually execute the steps of: determining the sensed parameter of the battery; determining a parameter threshold of the battery. If the sensed parameter of the battery is the same or exceeds the parameter threshold, decreasing the groundspeed to a predetermined safe speed. If the sensed parameter of the battery is below the parameter threshold, determining the change in the parameter which would be caused by the regenerative braking system at the current groundspeed of the vehicle. If the change in the parameter would cause the sensed parameter to reach or exceed the parameter threshold, decreasing the groundspeed of the vehicle to one at which the change in the parameter caused by the regenerative braking system would cause the sensed parameter to approximate but not exceed the parameter threshold of the battery. If the change in the parameter would cause the sensed parameter to remain within the parameter threshold, increasing the groundspeed of the vehicle to one at which the change in the parameter caused by the regenerative braking system would cause the sensed parameter to approximate but No. not exceed the parameter threshold of the battery and which does not exceed the maximum operating groundspeed.

[0008] In another aspect of the present invention, there is provided a controller for use in association with a power system of a battery-powered electric vehicle to achieve dynamic speed modulation in extended braking applications. The power system of the electric vehicle comprises: at least one electric motor operatively connected to a drive train of the vehicle; a rechargeable battery for supply of power to the at least one electric motor; and a regenerative braking system operatively connected to the at least one electric motor which progressively limits the groundspeed of the vehicle and provides recharging power to the battery. The controller contains a processor and control software and is operatively connected to the power system of the electric vehicle so as to be capable of: monitoring the sensed parameter of the battery, and the current groundspeed of the vehicle; determining a change in the parameter which would be caused by the regenerative braking system at the current groundspeed of the vehicle; and adjusting the current groundspeed of the vehicle between zero and a maximum operating groundspeed.

[0009] The controller, during operation of the vehicle, facilitates the dynamic speed modulation in extended braking applications by continually executing the steps of: determining the sensed parameter of the battery; determining a parameter threshold of the battery. If the sensed parameter of the battery is the same or exceeds the parameter threshold, reducing the maximum groundspeed to a predetermined safe speed. If the sensed parameter of the battery is below the parameter threshold, determining the change in the parameter which would be caused by the regenerative braking system at the current groundspeed of the vehicle. If the change in the parameter would cause the sensed parameter to reach or exceed the parameter threshold, decreasing the groundspeed of the vehicle to one at which the change in the parameter caused by the regenerative braking system would cause the sensed parameter to approximate but not exceed the parameter threshold of the battery. If the change in the parameter would cause the sensed parameter to remain within the parameter threshold, increasing the groundspeed of the vehicle to one at which the change in the parameter caused by the regenerative braking system would cause the sensed parameter to approximate but not exceed the parameter threshold of the battery and which does not exceed the maximum operating groundspeed.

[0010] In a further aspect of the present invention, there is provided a battery powered electric vehicle configured to achieve dynamic speed modulation in extended braking applications, said vehicle comprising: at least one electric motor operatively connected to a drive train of the vehicle; a rechargeable battery for supply of power to the at least one electric motor; and a regenerative braking system operatively connected to the at least one electric motor which progressively limits the groundspeed of the vehicle and provides recharging power to the battery; and a controller for use in association with a power system of the vehicle comprising a processor and associated control software, being operatively connected to the power system of the electric vehicle so as to be capable of: monitoring a sensed parameter of the battery, and the current groundspeed of the vehicle; determining a change in the parameter which would be caused by the regenerative braking system at the current groundspeed of the vehicle; and adjusting the current groundspeed of the vehicle between zero and a maximum operating groundspeed.

[0011] The controller, during operation of the vehicle, facilitates the dynamic speed modulation in extended braking applications by continually executing the steps of: determining the sensed parameter of the battery; determining a parameter threshold of the battery. If the sensed parameter of the battery is the same or exceeds the parameter threshold, decreasing the groundspeed to a predetermined safe speed. If the sensed parameter of the battery is below the parameter threshold, determining the change in the parameter which would be caused by the regenerative braking system at the current groundspeed of the vehicle. If the change in the parameter would cause the sensed parameter to reach or exceed the parameter threshold, decreasing the groundspeed of the vehicle to one at which the change in the parameter caused by the regenerative braking system would cause the sensed parameter to approximate but not exceed the parameter threshold of the battery. If the change in the parameter would cause the sensed parameter to remain within the parameter threshold, increasing the groundspeed of the vehicle to one at which the change in the parameter caused by the regenerative braking system would cause the sensed parameter to approximate but not exceed the parameter threshold of the battery and which does not exceed the maximum operating groundspeed. CA Description of the drawings:

[0012] While the invention is claimed in the concluding portions, preferred embodiments are provided in the detailed description which may be best understood with the diagrams where like parts in each of the several diagrams are labeled with like numerals, and where:

[0013] FIGURE 1 is a flow chart demonstrating the steps involved in one embodiment of the method of the present invention;

[0014] FIGURE 2 is a flowchart demonstrating the steps involved in an alternate embodiment of the method of the present invention, on a vehicle including a charging resistor;

[0015] FIGURE 3 is a schematic diagram of an electric vehicle in accordance with the present invention; and

[0016] FIGURE 4 is a block diagram of the components of one embodiment of a controller in accordance with the present invention. Detailed Description of Illustrated Embodiments:

[0017] As outlined above, the invention comprises a method of dynamic speed modulation in a battery- powered electric vehicle in extended braking applications, such as downhill running and the like, to avoid power system damage to the vehicle by application of regenerative braking at excessive groundspeeds, while permitting full torque operation of the motors on the vehicle during governed running of the motors. .

[0018] It is specifically contemplated that the method in the apparatus outlined herein would be useful in electric vehicle applications where safety is a key element of operation, as well as where power system failures requiring repair are problematic as the distance of the vehicle from a maintenance base extends. For example, in underground mining applications, electric vehicles can travel down extended ramps for large distances underground. If battery failure or power system repair of the vehicle took place a long way from the operating base of the vehicle underground, that could require the travel of maintenance assets through many miles of underground tunnels away from the point of failure.

[0019] One of the primary extended braking applications contemplated under the method of the present invention is in extended downhill running applications, including mining applications and the like. It will be understood, however, that any number of different applications and types of battery-powered electric vehicles would be encompassed within the intended scope of the present invention. As well, virtually any type of a battery-powered electric vehicle within the scope of that defined herein, that encompasses a regenerative braking system, could be benefited by the installation of a control environment and control system in accordance with the present invention. CA Method Overview:

[0020] As outlined above, the invention comprises a method of dynamic speed modulation for use in extended braking applications in a battery-powered electric vehicle. Operation of the vehicle in accordance with the method of the present invention results in the avoidance of power system damage from excessive regenerative braking power generation or application to the battery of the vehicle, and permits the operation of the vehicle at full motor torque even when the speed of the vehicle is governed to limit the regenerative braking application to the battery.

[0021] As described throughout, the method of the present invention is effectively achieved by the incorporation of a controller with software capable of applying the control method of the present invention within the power and control system of the electric vehicle.

[0022] The controller, as described in further detail below, includes a processor and control software instructions thereon which are capable of monitoring a sensed parameter of the battery, and the current groundspeed of the vehicle, calculating or determining a change in the parameter which would be caused by the regenerative braking system at the current groundspeed the vehicle, and adjusting the current groundspeed of the vehicle, between zero and a maximum operating groundspeed. CA

[0023] The method of the present invention will effectively be achieved by operation of the controller during operation of the power system of the vehicle to conduct a continuous and real time monitoring and control loop as outlined below.

[0024] This controller may be part of an electric vehicle, as also described in further detail below. The electric vehicle includes at least one electric motor operatively connected to a drive train of the vehicle, a rechargeable battery for supply of power to the at least one electric motor, and a regenerative braking system operatively connected to the at least one electric motor which progressively limits the groundspeed of the vehicle and provides power to the battery. "Recharging power" is used herein to refer to the power that would be produced by the regenerative braking system at the current groundspeed of the vehicle.

[0025] The method generally comprises using the controller to continually execute the steps of: determining the sensed parameter of the battery, determining a parameter threshold of the battery. If the sensed parameter of the battery is the same or exceeds the parameter threshold, the method includes decreasing the groundspeed to a predetermined safe speed. If the sensed parameter of the battery is below the parameter threshold, the method includes determining the change in the parameter which would be caused by the regenerative braking system at the current groundspeed of the vehicle. If the change in the parameter would cause the sensed parameter to reach or exceed the parameter threshold, the method includes decreasing the groundspeed of the vehicle to one at which the change in the parameter caused by the regenerative braking system would cause the sensed parameter to approximate but not exceed the parameter threshold of the battery. If the change in the parameter would cause the sensed parameter to remain within the parameter threshold, increasing the groundspeed of the vehicle to one at which the change in the parameter caused by the regenerative braking system would cause the sensed parameter to approximate, but not exceed, the parameter threshold of the battery. In such a case, the groundspeed does not exceed the maximum operating groundspeed.

[0026] In the embodiment shown in Figure 1, the sensed parameter of the battery is a current energy level of the battery, the change in the parameter of the battery is the recharging power which would be produced by the regenerative braking system at the current groundspeed of the vehicle, and the parameter threshold of the battery is a maximum energy level that the battery can safely contain. In such applications, the difference between the maximum energy level and the current energy level of the battery is a referred to herein as the "charging capacity" of the battery, or the maximum amount of additional energy the battery is capable of safely receiving at a given time.

[0027] Typically, the regenerative braking system will apply torque to the motor to limit the groundspeed of the vehicle. This braking generates or provides recharging power that may be stored in the battery. The controller outlined above would be connected also to the control system or power system of the vehicle to permit the monitoring, calculating, and of adjusting control functions outlined above. CA

[0028] Referring back to Figure 1, Figure 1 illustrates one embodiment of the monitoring or method loop which could be effected or achieved by the controller of the present invention. The opening of the monitoring loop is shown at step 1-1. The controller, shown at step 1-2 of the monitoring loop, would determine the charging capacity 6 at that present time, that being the maximum amount of additional energy that the battery is capable of safely receiving at that time. This would be done by the controller 5 in conjunction with the battery and other components of the control or power system on the vehicle 1 by testing the amount of charging or additional energy that the batteries are capable of receiving at that time (i.e. the inverse of the current filled capacity of the battery at that time). The charging capacity, or the maximum additional energy that the batteries can safely receive, can be determined based on many measured and calculated parameters, such as battery state of charge, voltage, and temperature.

[0029] For example, the available recharging power may be determined by counting battery current (which is measured with a current sensor) over time. Several temperature sensors are distributed within the battery module to determine maximum and minimum cell temperatures. A battery management system measures each cell voltage within the battery with voltage sensors. Internal resistance is calculated as the cell voltages change with changes in battery current.

[0030] The term Charge Current Limit (CCL) is often used when determining how much regenerative current can be supplied to the battery safely. CCL can be reduced if the state of charge is high, if the battery temperature is high or low, or if the calculated cell resistance is high. Once the CCL is determined, it is compared to the optimal CCL. The optimal CCL is a CA CCL which allows charging at a rate that will prevent over-charging any cell within the tolerance of the time steep control loop.

[0031] If the charging capacity 6 is zero (i.e. if the batteries are incapable of receiving any additional energy at the present time) then the controller 5, via its connection to the remainder of the control system of the vehicle 1, adjusts or reduces the groundspeed 8 of the vehicle down to a predetermined safe (minimum) speed.

[0032] For example, while traveling downhill, the regenerative braking applies torque to the motor to slow and / or to maintain a predefined safe speed limit. In some applications, this safe minimum speed limit may be between, and including, 0 km / hr to 6 km / hr. The safe speed limit is determined by the rate of power dissipation of the vehicles systems and brake resistor, compared the slope of the hill, weight of the vehicle, and speed of the vehicle.

[0033] The testing of the charging capacity 6 is shown at decision block 1-3 in the diagram, and the reduction of groundspeed of the vehicle to the safe minimum speed is shown at 1-4. If the controller triggers the reducing of maximum groundspeed 8 down to the safe (minimum) speed, the continuation of the control or monitoring loop is also shown.

[0034] If the charging capacity 6 of the battery at the time of testing is more than zero, the NO leg of the 1-3 decision block would be followed. The controller 5 at that point would determine the (available) recharging power 7, shown at 1-5 (which is the power that would be produced by the regenerative braking system at the current groundspeed of the vehicle).

[0035] Following the determination of the available recharging power 7, the next step in the method is to determine whether the recharging power 7 exceeds the charging capacity 6 (i.e. at the current groundspeed the vehicle, will the regenerative brakes produce more power than the batteries are capable of safely receiving). This decision block is shown at 1-6. If it is determined by the controller that the available recharging power 7 (produced by the regenerative brakes) does not exceed the charging capacity 6 of the battery (i.e. the additional energy that the battery can safely receive), this is an indicator that the groundspeed of the vehicle could, if desired by the operator, be increased. The controller may then increase the groundspeed 8 of the vehicle to a speed at which the recharging power 7 produced by the regenerative brakes will be closer to approximate the charging capacity 6 of the battery. Increasing the groundspeed 8 of the vehicle is shown at step 1-7. It is understood that the groundspeed of the vehicle corresponds to, or is proportional to, the recharging power 7 produced by the regenerative brakes.

[0036] In that regard, the higher / increased maximum groundspeed may be determined through calculation of a new CCL. As CCL is increased, the maximum allowable groundspeed may also be increased. For example, if CCL goes from 200 amps to 250 amps, the maximum allowable ground speed may increase from 10 km / h to 13 km / h. The top end of the range of the desired maximum speed of a vehicle may be around 30 km / h. Traveling faster than this while on steep grades may be dangerous for the vehicle and the driver.

[0037] If the recharging power 7 produced by the regenerative brakes does exceed the charging capacity 6 of the batteries, ), the groundspeed 8 of the vehicle could be adjusted by the controller, shown at 1-8, to decrease to a point that the recharging power 7 produced by the regenerative brakes would approximate or be equal to the charging capacity 6 of the batteries. In other words, if the CCL is reduced, the speed limit of the vehicle would also be reduced.

[0038] For example, in some applications, the math of the control software might be adjusted to also capture scenarios in which the available recharging power 7 approximates or is reaching the maximum recharging capacity 6 without exceeding it.

[0039] The continuation of the controller monitoring loop is shown at 1-9. This method would be applied or executed by the controller in conjunction with the remainder of the components of the vehicle during the operation of the power system of the vehicle.

[0040] Figure 2 demonstrates an alternate approach to the method of the present invention with a different type of vehicle, namely a battery-powered electric vehicle that includes a charging resistor to deplete excess power from the regenerative braking system. The charging resistor may also be referred to as a brake resistor to deplete power from the battery. It may simply be an electric resistor that turns stored energy into heat.

[0041] Figure 2 is the same as Figure 1 in terms of the steps of the method, except that it shows at step 2-2 that the depletion capacity of the charging resistor is incorporated into the calculation of the charging capacity 6, i.e. the additional energy the batteries can safely receive. The charging resistor may be included for depletion of excess recharging power. When the vehicle include the charging resistor, the controller may limit the groundspeed of the vehicle once recharging power 7 exceeds the aggregate of the charging capacity 6 and the amount of recharging power which the charging resistor can receive and deplete.

[0042] The remainder of the method will operate similarly to that of Figure 1.

[0043] In one example, a 2000 kg vehicle that is traveling down a 20% grade will experience <semantics>2000*0.20*9.81=3924<annotation encoding="application / x-tex">2000*0.20*9.81 = 3924< / annotation>< / semantics> N of force due to the acceleration due to gravity. If the vehicle was traveling at 2 m / s, it would experience a mechanical power of 3924*2 = 7848 W. Assuming that the vehicle can convert 75% of that to battery power, <semantics>7848*0.75=5886<annotation encoding="application / x-tex">7848*0.75 = 5886< / annotation>< / semantics> W of that power that would go to charging the battery and / or be dissipated through the brake resistor. The other 25% of the power would be consumed through losses like rolling resistance, aerodynamic drag, viscous drag, gear losses, electrical losses and operating any other electrical equipment on the vehicle.

[0044] In such conditions, a 5886 W brake resistor could be used to maintain the vehicle at 2 m / s, for example. If the vehicle speed was allowed to be 8 m / s, then the power required would be over 23 kW. If the battery was in optimal condition, regenerating 23 kW and maintaining that speed would generally not be a problem However, if the battery was full, cold, hot, or had a high internal resistance, then 23 kW cannot be safely stored in the battery, since it will be full in a short period of time or it will exceed its charge current limit. In this manner, adaptive speed control may be used to keep the power level lower when the battery cannot be charged at higher rates.

[0045] Further embodiments of the method could be created which permit the incorporation of inputs to the controller such that the controller could determine or factor in the application of a secondary braking system on a particular electric vehicle. Application of the secondary braking system in an electric vehicle may result in less of a need for regenerative braking to be applied. It will be understood that the calculations executed by the software on the controller could be modified by those skilled in the art to accommodate testing for the application of the secondary braking system during the monitoring loop such as that shown in Figure 1 and Figure 2.

[0046] In another embodiment of the present method (not shown in the Figures), rather than monitoring and determining the current energy level of the battery, the charging capacity of the battery, and the recharging power produced by the regenerative braking system, the present method may instead by performed based on the temperature of the battery.

[0047] In that regard, the sensed parameter of the battery would be the temperature of the battery. The change in the parameter of the battery would be the change in temperature of the battery which would be caused by the regenerative braking system at the current groundspeed of the vehicle. And the parameter threshold of the battery would be a maximum allowable safe temperature of the battery. .5 Vehicle:

[0048] Figure 3 is a schematic drawing of the key components of the power and control system of a battery-powered electric vehicle 1 in accordance with an aspect of the present invention. The vehicle platform comprises at least one electric motor 2 operatively connected to the drivetrain 3 of the vehicle 1. A rechargeable battery 4 is also shown. The vehicle 1 includes a regenerative braking system 10 which is operatively connected to the at least one electric motor 2 and which is configured to limit the groundspeed of the vehicle and provide recharging power to the battery 4. The controller 5 of the present invention is also shown. The controller 5 is operatively connected to the power control bus of the vehicle or otherwise to the necessary electrical and control components. It will be understood that there are numerous different combinations, configurations and types of battery-powered electric vehicles could be encompassed within the scope of the present invention and all are contemplated within the scope hereof.

[0049] The vehicle 1, via operation of the controller 5 when the vehicle 1 is powered and operating, will operate in accordance with the method of the present invention as outlined above.

[0050] The controller 5 could be manufactured as part of a new electric vehicle on an OEM basis, or the electric vehicle 1 could be a pre-existing electric vehicle, in which the controller 5 would be retrofitted to permit the practice of the method of the present invention in accordance with the pre-existing vehicle. Both such approaches are contemplated within the scope of the present invention. Controller:

[0051] Controller 5 could be incorporated into new or existing vehicles. The controller 5 will comprise a hardware component capable of connection with the remainder of the power system of a battery-powered electric vehicle to permit the practice of the method of the present invention.

[0052] The design of programmable logic controllers, hardware controllers and related software for the control of various industrial machinery, vehicles and the like will be understood by those skilled in the art and the specifics of the hardware will be understood to potentially vary. The controller 5 will effectively comprise a capable processor with associated memory and processor instructions including control software for the facilitation of the method of the present invention thereon.

[0053] Figure 4 is a block diagram demonstrating the components of one embodiment of the controller 5 in accordance with the present invention. There is shown a processor 15, memory 16 which contains various required processor instructions including the control software 17 for facilitation of the method of the present invention, as well as a necessary power supply connection 19 to the power supply on the vehicle. A bus connector 18 is shown, which is one contemplated method of integration of the controller 5 into the remainder of the system of the vehicle 1. In other embodiments of vehicle 1, the controller 5 could be individually connected as required to the required components of the vehicle 1, namely the battery system and a sensor for groundspeed at a minimum where the behavior of the regenerative braking system was already known.

[0054] Although the present technology has been described for illustration based on what is currently considered the most practical and preferred implementations, it is to be understood that such detail is solely for that purpose and that the technology is not limited to the disclosed implementations. For example, it is to be understood that the present technology contemplates that, to the extent possible, one or more features of any implementation can be combined with one or more features of any other implementation.

[0055] In addition, it will be apparent to those of skill in the art that by routine modification the present invention can be optimized for a wide range of conditions and application. It will also be appreciated by those of skill in the art that there are various ways to produce, and designs for, the apparatus and methods of the present invention. The illustrated embodiments are therefore not intended to limit the invention, but to provide examples of the apparatus and method to enable those of skill in the art to appreciate the inventive concept. . CA

Claims

<pat:ClaimStatement>Claims:< / pat:ClaimStatement> <pat:Claims com:id="claims"> <pat:Claim com:id="CLM-00001"> <pat:ClaimNumber>1< / pat:ClaimNumber> <pat:ClaimText>1. A method of dynamic speed modulation in a battery-powered electric vehicle, the method comprising the steps of: determining, by a processor, a sensed parameter of a rechargeable battery of the battery-powered electric vehicle; determining, by a processor, a threshold of the rechargeable battery; and performing, by the processor: when the sensed parameter of the rechargeable battery is less than the threshold, determining a change in the sensed parameter by recharging power generated by the regenerative braking system at the groundspeed of the vehicle, and performing, by the processor, one of; a. when the change causes the sensed parameter to reach or exceed the threshold, decreasing, by using a friction brake, the groundspeed of the vehicle to a second groundspeed at which the change causes the sensed parameter to approximate but not exceed the threshold; and b. when the change causes the sensed parameter to remain within the threshold, decreasing the groundspeed of the vehicle to a third groundspeed at which the change caused by the regenerative braking system causes the sensed parameter to approximate but not exceed the threshold of the battery and which does not exceed a maximum operating groundspeed; wherein: the sensed parameter of the rechargeable battery comprises a temperature of the battery, the change comprises a change in temperature of the rechargeable battery caused by the regenerative braking system at the groundspeed of the vehicle, and the threshold of the rechargeable battery further comprises a maximum allowable temperature of the rechargeable battery. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00002"> <pat:ClaimNumber>2< / pat:ClaimNumber> <pat:ClaimText>2. The method of Claim 1, wherein the sensed parameter of the battery is a current energy level of the rechargeable battery, the change comprises recharging power produced by the regenerative braking system at the groundspeed of the vehicle, and the threshold of the rechargeable battery is a maximum energy level that the rechargeable battery contains, and a difference between the maximum energy level and the current energy level of the rechargeable battery is a charging capacity of the rechargeable battery, or the amount of additional energy that the rechargeable battery is capable of receiving at a given time. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00003"> <pat:ClaimNumber>3< / pat:ClaimNumber> <pat:ClaimText>3. The method of Claim 1 wherein the speed limit is 0 km / hr. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00004"> <pat:ClaimNumber>4< / pat:ClaimNumber> <pat:ClaimText>4. The method of Claim 1 wherein the speed limit is 6 km / hr. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00005"> <pat:ClaimNumber>5< / pat:ClaimNumber> <pat:ClaimText>5. The method of Claim 2 further comprises depleting excess recharging power at a charging resistor and decreasing the groundspeed of the vehicle once recharging power exceeds the charging capacity of the rechargeable battery and an amount of recharging power which the charging resistor receives and depletes. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00006"> <pat:ClaimNumber>6< / pat:ClaimNumber> <pat:ClaimText>6. The method of Claim 1 wherein the battery-powered electric vehicle runs downhill. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00007"> <pat:ClaimNumber>7< / pat:ClaimNumber> <pat:ClaimText>7. A controller for use in association with a power system of a battery-powered electric vehicle to achieve dynamic speed modulation in extended braking applications, the controller configured for: a) determining a sensed parameter of a rechargeable battery of the battery- powered electric vehicle; b) determining a threshold of the rechargeable battery; and c) performing: when the sensed parameter of the rechargeable battery is less than the threshold, determining a change in the sensed parameter by recharging power generated by the regenerative braking system at the groundspeed of the vehicle, and performing one of a. when the change causes the sensed parameter to reach or exceed the threshold, decreasing, by using a friction brake, the groundspeed of the vehicle to a second groundspeed at which the change causes the sensed parameter to approximate but not exceed the threshold of the battery; and b. when the change causes the sensed parameter to remain within the threshold, decreasing the groundspeed of the vehicle to a third groundspeed at which the change caused by the regenerative braking system causes the sensed parameter to approximate but not exceed the threshold of the rechargeable battery and which does not exceed a maximum operating groundspeed; wherein: the sensed parameter of the rechargeable battery comprises a temperature of the rechargeable battery, the change comprises a change in temperature of the rechargeable battery caused by the regenerative braking system at the groundspeed of the vehicle, and the threshold of the rechargeable battery further comprises a maximum allowable temperature of the rechargeable battery. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00008"> <pat:ClaimNumber>8< / pat:ClaimNumber> <pat:ClaimText>8. The controller of Claim 7 wherein the sensed parameter of the rechargeable battery is current energy level of the rechargeable battery, the change comprises the recharging produced by the regenerative braking system at the groundspeed of the vehicle, and the threshold of the rechargeable battery is a maximum energy level that the rechargeable battery contains, and a difference between the maximum energy level and the current energy level of the battery is a charging capacity of the battery, or the amount of additional energy the battery that is capable of receiving at a given time. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00009"> <pat:ClaimNumber>9< / pat:ClaimNumber> <pat:ClaimText>9. The controller of Claim 7 wherein the speed limit is 0 km / hr. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00010"> <pat:ClaimNumber>10< / pat:ClaimNumber> <pat:ClaimText>10. The controller of Claim 7 wherein the speed limit is 6 km / hr. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00011"> <pat:ClaimNumber>11< / pat:ClaimNumber> <pat:ClaimText>11. The controller of Claim 8 further configured for depleting excess recharging power at a charging resistor, and decreasing the groundspeed of the vehicle once recharging power exceeds the charging capacity of the rechargeable battery and an amount of recharging power which the charging resistor receives and depletes. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00012"> <pat:ClaimNumber>12< / pat:ClaimNumber> <pat:ClaimText>12. The controller of Claim 7 wherein the battery-powered electric vehicle runs downhill. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00013"> <pat:ClaimNumber>13< / pat:ClaimNumber> <pat:ClaimText>13. A battery-powered electric vehicle configured to achieve dynamic speed modulation in extended braking applications, said vehicle comprising: a. at least one electric motor operatively connected to a drive train of the vehicle; b. a rechargeable battery for supply of power to the at least one electric motor; and c. a regenerative braking system operatively connected to the at least one electric motor which progressively limits a groundspeed of the vehicle and provides recharging power to the battery; and d. a controller for use in association with a power system of the vehicle comprising a processor and associated control software, being operatively connected to the power system of the electric vehicle, the controller configured for: a. determining a sensed parameter of a rechargeable battery of the battery-powered electric vehicle; b. determining a threshold of the rechargeable battery; and c. performing: when the sensed parameter of the rechargeable battery is less than the threshold, determining a change in the sensed parameter by recharging power generated by the regenerative braking system at the groundspeed of the vehicle, and performing one of a. when the change causes the sensed parameter to reach or exceed the threshold, decreasing, by using a friction brake, the groundspeed of the vehicle to a second groundspeed at which the change causes the sensed parameter to approximate but not exceed the threshold of the battery; and b. when the change causes the sensed parameter to remain within the threshold, decreasing the groundspeed of the vehicle to a third groundspeed at which the change caused by the regenerative braking system causes the sensed parameter to approximate but not exceed the threshold of the rechargeable battery and which does not exceed a maximum operating groundspeed, wherein: the sensed parameter of the rechargeable battery comprises a temperature of the rechargeable battery, the change comprises a change in temperature of the rechargeable battery caused by the regenerative braking system at the groundspeed of the vehicle, and the threshold of the battery is a maximum allowable temperature of the battery. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00014"> <pat:ClaimNumber>14< / pat:ClaimNumber> <pat:ClaimText>14. The vehicle of Claim 13 wherein the sensed parameter of the rechargeable battery is a current energy level of the rechargeable battery, the change is the recharging power produced by the regenerative braking system at the groundspeed of the vehicle, and the threshold of the rechargeable battery is a maximum energy level that the rechargeable battery contains, and a difference between the maximum energy level and the current energy level of the battery is a charging capacity of the battery, or the amount of additional energy the battery that is capable of receiving at a given time. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00015"> <pat:ClaimNumber>15< / pat:ClaimNumber> <pat:ClaimText>15. The vehicle of Claim 13 wherein the speed limit is 0 km / hr. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00016"> <pat:ClaimNumber>16< / pat:ClaimNumber> <pat:ClaimText>16. The vehicle of Claim 13 wherein the speed limit is 6 km / hr. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00017"> <pat:ClaimNumber>17< / pat:ClaimNumber> <pat:ClaimText>17. The vehicle of Claim 14 further configured for: depleting excess recharging power at a charging resistor, and decreasing the groundspeed of the vehicle once recharging power exceeds the charging capacity of the rechargeable battery and an amount of recharging power which the charging resistor receives and depletes. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00018"> <pat:ClaimNumber>18< / pat:ClaimNumber> <pat:ClaimText>18. The method of Claim 1 further comprises the step of performing, by the processor, when the sensed parameter of the rechargeable battery is equal to or greater than the threshold, decreasing the groundspeed of the vehicle to a speed limit using the friction brake. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00019"> <pat:ClaimNumber>19< / pat:ClaimNumber> <pat:ClaimText>19. The controller of Claim 7 further comprises the controller configured for performing when the sensed parameter of the rechargeable battery is equal to or greater than the threshold, decreasing the groundspeed of the vehicle to a speed limit using the friction brake. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00020"> <pat:ClaimNumber>20< / pat:ClaimNumber> <pat:ClaimText>20. The vehicle of Claim 13 further comprises the controller configured for when the sensed parameter of the rechargeable battery is equal to or greater than the threshold, decreasing the groundspeed of the vehicle to a speed limit using the friction brake. < / pat:ClaimText> < / pat:Claim> < / pat:Claims>