Abstract:
A solar kit according to an exemplary aspect of the present disclosure includes, among other things, a solar module including a solar cell. A converter is configured to provide a continuous amount of power from said solar module to a battery pack.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/661,056, which was filed on 18 Jun. 2012 and is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    This disclosure generally relates to an electrical vehicle. More particularly, this disclosure relates to a solar roof kit for charging a battery pack of an electric vehicle. 
         [0003]    A battery pack for an electric vehicle is charged using various approaches known in the industry. In one approach, a battery pack for a golf cart is connected to a grid interface to charge the battery pack. In another approach, a solar module is mounted to the electric vehicle to provide power to the battery pack. Power from the solar module is regulated by a controller, such as a Maximum Power Point Tracking (MPPT) system. The MPPT system maximizes the amount of power produced by each solar cell of the solar module by maintaining a predetermined operating voltage independent of the battery voltage. However, existing MPPT controllers do not provide a continuous charge to the battery pack, thereby resulting in a reduced operating life of the battery pack. 
       SUMMARY 
       [0004]    A solar kit according to an exemplary aspect of the present disclosure includes, among other things, a solar module including a solar cell having a non-linear rate of current output with respect to an instantaneous voltage of the solar cell. A converter is configured to provide a continuous amount of power from the solar module to a battery pack. 
         [0005]    An electric vehicle according to an exemplary aspect of the present disclosure includes, among other things, a battery pack including a battery cell. A solar module includes a solar cell having a non-linear rate of current output with respect to an instantaneous voltage of the solar cell. A converter is configured to provide a continuous amount of power from the solar module to the battery pack. 
         [0006]    A method of charging a battery according to another exemplary aspect of the present disclosure includes, among other things, connecting a solar cell to a battery, the solar cell having a non-linear rate of current output with respect to an instantaneous voltage of the solar cell, and providing a continuous amount of current from the solar cell to the battery. 
         [0007]    These and other features disclosed herein can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  illustrates a side view of an electric vehicle solar roof kit mounted to an electric vehicle. 
           [0009]      FIG. 2A  illustrates a schematic view of the electric vehicle solar roof kit of  FIG. 1 . 
           [0010]      FIG. 2B  illustrates a schematic view of a second example of the electric vehicle solar roof kit of  FIG. 1 . 
           [0011]      FIG. 3  illustrates a visual display of the solar roof kit of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]      FIG. 1  illustrates a side view of an electric vehicle solar roof kit  10  mounted to an electric vehicle  11 . In one example, the electric vehicle  11  is a golf cart. In another example, the electric vehicle  11  is a transit bus. In yet another example, the electric vehicle  11  is a railed vehicle system. Referring to  FIG. 2A , the electric vehicle  11  includes a battery pack  45  for providing an amount of power to an electric motor  14 . Generally, the battery pack  45  includes at least one battery cell  46 . In one example, the electric vehicle  11  includes a regenerative braking system  15  configured to supply an amount of current to the battery pack  45 . 
         [0013]    The solar roof kit  10  includes a solar module  20 . The solar module  20  includes a plurality of solar cells  25  (shown schematically) connected in series to each other. In one example, each of the solar cells  25  is a polycrystalline construction. Alternatively, the solar cells  25  may be of any other suitable construction, such as a monocrystalline construction. In one example, the solar module  20  has a substantially rectangular configuration and is mounted adjacent to a roof  12  of the electric vehicle  11 . It should be appreciated that the solar module  20  may be configured in any combination of shape and dimension. The solar cells  25  of the solar module  20  are connected to a wire harness  26 . The wire harness  26  is connected to a step-up converter  40  by a pair of first converter lines  30 ,  35 . 
         [0014]    The step-up converter  40  is operative to convert an input signal to an output signal having a greater direct current (DC) voltage than the input signal. In one example, the step-up converter  40  includes an inductor, a high speed switch such as a transistor, at least one capacitor, and a diode each connected to an integrated circuit board. The step-up converter  40  converts an open current voltage of the solar module  20  to a predetermine float voltage. The step-up converter  40  is connected to a positive terminal of the battery pack  45  by a second converter line  52  to provide an amount of current at the predetermined float voltage. Generally, the predetermined float voltage is defined as a value within a range of operating voltages of each battery cell  46  as determined by one of ordinary skill in the art. In one example, the predetermined float voltage is approximately 39.2 volts when the battery pack  45  operates at 36 volts or approximately 56.6 volts when the battery pack  45  operates at 48 volts. The predetermined float voltage can be within a suitable range for the battery pack  45 , with the suitable range being determined by one skilled in the art having the benefit of this disclosure. 
         [0015]    The step-up converter  40  outputs a continuous current to the battery pack  45 . In this arrangement, the solar module  20  provides the continuous current to the battery pack  45  even though the solar module  20  may be operating in an off-peak state. The operation of the solar module  20  in the off-peak state is a result of each of solar cells  25  having a non-linear rate of current output with respect to an instantaneous voltage. Thus, the solar module  20  may operate in the off-peak state when each of the solar cells  25  discharges an amount of current when the instantaneous voltage of the solar cells  25  at a current time is below a predetermined operating voltage. Thus, it should be understood that the solar cells  25  may charge more efficiently when the instantaneous voltage is greater than or approximately equal to the predetermined operating voltage. In one example, the continuous current to the battery pack  45  is approximately 7.0 amps. 
         [0016]    A continuous current provides the battery pack  45  with a continuous charge as long as the solar module  20  is operational, thereby eliminating the need to connect the battery pack  45  to a power source external to the electric vehicle  11  to charge the battery pack  45 . In one example, the step-up converter  40  includes a bypass circuit connected to the output terminals of the step-up converter  40  for conditioning the output voltage of the step-up converter  40  and to protect the step-up converter  40  from a reverse current of the battery pack  45 . In one example, the solar roof kit  10  includes a high-power shunt  50  connected to the step-up converter  40  by a third converter line  54 . The high-power shunt  50  is connected to a negative terminal  51  of a motor controller  55  of the electric vehicle  11  by a first controller line  56 . The motor controller  55  is electrically connected to a positive terminal  53  of the battery pack  45  by a second controller line  57 , and a negative terminal of the battery pack  45  is electrically connected to the high-power shunt  50  at a battery line  60 . 
         [0017]    Referring to  FIG. 2B , the solar roof kit  10  may include a secondary storage device  68   a  configured to receive an amount of energy from the solar module  20 . The secondary storage device  68   a  may provide an amount of energy to the battery pack  45  or to the electric motor  52 . An amount of energy may be provided to the secondary storage device  68   a  when the battery pack  45  is charging. An amount of energy may also be provided to the secondary storage device  68   a  when the battery pack  45  is fully charged and thereby recirculates an amount of current to the solar module  20 . In this arrangement, the energy is stored in the secondary storage device  68   a  rather than being dissipated as heat in the solar cells  25  of the solar module. 
         [0018]    In one example, the secondary storage device  68   a  is a capacitor. In another example, the secondary storage device  68   a  is a spare battery pack including at least one battery cell. The secondary storage device  68   a  is arranged between the motor controller  55  and the shunt  50  and in parallel to the battery pack  45 . In other examples, any of the locations  68   b,    68   c  and  68   d  can be used in the place of the secondary storage device  68   a,  as shown by dotted lines in  FIG. 2B . However, other locations of the secondary storage device  68   a  are contemplated. In other examples, more than one secondary storage device  68   a  is used. 
         [0019]    In one example, the solar roof kit  10  includes an electrical vehicle gauge  75  for observing the status of the battery pack  45 . The gauge  75  includes a first controller (not shown) for calculating and storing a number of operating conditions of the electric vehicle  11  for later retrieval. The first controller may include, but is not limited to, a microprocessor or a single board computer. The gauge  75  calculates an amount of current being consumed by the motor  14  of the electric vehicle  11  and an amount of regenerative current being supplied to the battery pack  45  from the solar module  20  and the regenerative braking system  15  of the electric vehicle  11  based upon the voltages measured at the shunt  50 . 
         [0020]    Referring to  FIG. 3 , the gauge  75  may include a visual display  77  connected to the computing device for displaying the operating conditions to an operator of the vehicle  11 . In one example, the visual display  77  is a graphical user interface including a first window  78 , a second window  79  and a third window  80 . The first window  78  may display an amount of power being consumed by the motor  14 , the second window  79  may display an instantaneous voltage of the battery pack  45 , and the third window  80  may display an amount of regenerative current being supplied to the battery pack  45  from the solar module  20  and an estimated time for the battery pack  45  to be fully charged. However, the visual display  77  may be configured to display any operating condition observed by the gauge  75  and may include a different arrangement of the operating conditions. In another example, the visual display  77  includes a liquid crystal display (LCD). In another example, the visual display  77  includes a touch-screen configuration for responding to commands from the operator of the vehicle  11 . In another example, the gauge  75  includes a warning indicator  81  (shown schematically) for providing a status of at least one of the operating conditions to the operator of the vehicle  11 , such as a speaker for providing an audible signal when the charge of the battery pack  45  is less than a predetermined amount. In another example, the visual display  77  includes the warning indicator  81 . 
         [0021]    The gauge  75  is connected to each terminal of the high-power shunt  50  by a plurality of leads  65 ,  67 ,  70  for measuring the voltage across the terminals of the high-power shunt  50 . The gauge  75  receives the voltage of the high-power shunt  50  and calculates a corresponding amount of current flowing between the battery pack  45  and the motor controller  55  based on the measured voltages. The gauge  75  is also capable of calculating the battery pack voltage, power output, net amperage hours drawn from or regenerated to the battery pack, Watt-hours or total energy drawn from the battery pack  45 , Watt-hours produced from regenerative braking of the vehicle  11 , percentage of power regeneration provided by the solar module  20  and by brake regeneration from the vehicle  11  in comparison to the total consumption of power from the battery pack  45 , forward amp-hours and regenerative amperage-hours, peak regenerative current observed during operation, maximum amperage drawn from the battery pack  45 , voltage sag of the battery pack  45  as compared to a predetermined operating voltage, and a running sum and a total sum of the lifetime amperage-hours drawn from the battery pack  45  depending on the requirements of a particular system. In another example, the gauge  75  estimates a duration for achieving a full charge in the case of off-peak operation of the solar module  20 . 
         [0022]    In some examples, the gauge  75  measures an amount of regenerative power provided to the battery pack  45  when the electric vehicle  11  is connected or plugged into a grid. Thus, the gauge  75  may be operable to maintain a constant running total of the amount of power provided to and discharged by the battery pack  45  for real-time evaluation. For example, the gauge  75  may be operable to predict the life of the battery pack  45  or at least one of the battery cells  46 . In another example, the gauge  75  is operable to provide a recommended schedule for charging the battery pack  45  from the grid. 
         [0023]    The gauge  75  may be operable to perform one or more limiting functions to reduce the amount of power consumed by the motor  52 . The gauge  75  may include a first communications port  82  in electrical communication with a second communications port  83  of the motor controller  55  by way of a controller communications path  84 . The controller communications path  84  may be analog or digital. The controller communications path  84  may also be a wired connection or a wireless connection. The gauge  75  is operable to send one or more limiting instructions based upon the limiting function to the motor controller  55 . In one example, the limiting instruction is a desired speed of electric vehicle  11  corresponding to an output of the motor  52 . In another example, the limiting instruction is a maximum amount of amperage to be provided to the motor  52 . However, other limiting functions and limiting instructions are contemplated. 
         [0024]    The gauge  75  is electrically connected to a speedometer  85  by a speedometer line  90 . In one example, the speedometer  85  is mounted to a front wheel  13  (shown in  FIG. 1 ) of the vehicle  11  for measuring a quantity of the wheel rotations. The speedometer  85  is configured to provide a wheel rotation signal to the gauge  75  in response to a rotation of the wheel  13 . The gauge  75  calculates a distance traveled by the vehicle  11  as a function of the number of wheel rotations and a predetermined circumference of the wheel  13 . The gauge  75  is also operable to calculate trip time and total distance traveled by the vehicle  11 . In some examples, the gauge  75  calculates the current speed, average speed and maximum speed of the vehicle  11 . The gauge  75  also calculates Watt-hours consumed per kilometer and Watt-hours consumed per mile. 
         [0025]    In another example, the gauge  75  includes a data interface for transmitting the operating conditions of the vehicle  11  to a remote device  95  over a first communications path  96 . The data interface of the gauge  75  is configured to send and receive data over the first communications path  96  by one or more of universal serial bus (USB), Ethernet, Wi-Fi, Bluetooth, or any other configuration suitable for data communications. The remote device  95  is configured to send and receive data from the gauge  75  over a second communications path  99  to a dedicated server  100  for real-time monitoring and analysis of the electric vehicle  11 . The second communications path  99  may be Wi-Fi, cellular or Global Positioning Satellite Receiver (GPSr), or any other configuration suitable for data communications. In one example, the dedicated server  100  is capable of monitoring the operating condition of a plurality of electric vehicles  11  for fleet management and deployment. In another example, the dedicated server  100  can interface with the electric vehicle  11  and provide direct controls to the electric vehicle  11 . The server  100  can be any remote device configured to control the electric vehicle  11 . 
         [0026]    The foregoing is merely illustrative of the principles of this disclosure and various modifications may be made by those skilled in the art without departing from the scope of this disclosure. The above described embodiments are presented for purposes of illustration and not of limitation. The present disclosure also can take many forms other than those explicitly described herein. Accordingly, it is emphasized that this disclosure is not limited to the explicitly disclosed methods, systems, and apparatuses, but is intended to include variations to and modifications thereof, which are within the spirit of the present disclosure.