Abstract:
Batteries and battery monitoring and charging systems. The preferred battery has a plurality of rechargeable cells connected in series, first and second power terminals, each connected to a respective end of the series connection of rechargeable cells, a first connector for connecting to a battery charger, the first connector having connector contacts connected to each of the plurality of rechargeable cells, the first connector also having connector contacts coupled to a serial communication link, and a processor coupled to sense the voltage of each rechargeable cell and control the serial communication link for communication of rechargeable cell voltages when a charger is connected to the first connector. The charger communicates with the battery over the serial communication link to monitor cell temperature, and to charge each cell individually in a controlled manner. Various features and capabilities are disclosed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of battery powered vehicles. 
     2. Prior Art 
     Battery powered vehicles of various sizes and designs are well known in the prior art. Of particular interest to the present invention are the smaller vehicles wherein the battery may be recharged in the vehicle or removed for recharging while another battery is placed in the vehicle so that the vehicle may be used while recharging occurs. One such vehicle is the three-wheeled vehicle shown in  FIGS. 1   a  and  1   b . This vehicle is manufactured by T3 Motion, Inc., assignee of the present invention. 
     In small electric powered vehicles using a removable rechargeable battery, the battery typically is recharged through its power output terminals, whether in the vehicle or removed from the vehicle for recharging. This provides a simple and low cost way of recharging such batteries, though has certain disadvantages. First, the power output terminals of the battery must be readily accessible, creating a possible safety hazard on the inadvertent shorting of those power terminals. Also batteries typically are comprised of multiple cells connected in series, so that individual cells cannot be monitored through its power output terminals. Accordingly, the general health of the battery, its rate of self discharge, etc. can only be monitored on an overall battery basis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1   a  and  1   b  are views of a three wheeled electric vehicle in which the preferred embodiment of the present invention is used. 
         FIGS. 2   a  through  2   e  are illustrations of a battery and its mounting in the vehicle of  FIGS. 1   a  and  1   b  in accordance with the present invention. 
         FIG. 2   f  is a perspective view of a battery charger in accordance with the present invention. 
         FIG. 3  is a block diagram of each battery of  FIGS. 2   a  through  2   e.    
         FIGS. 4   a  and  4   b  are battery control flow charts in accordance with the present invention. 
         FIG. 5  is a charger block diagram for each of the two chargers in the charger of  FIG. 2   f.    
         FIGS. 6 ,  7  and  8  are charger control flow charts in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 2   a  is a perspective view of the chassis of the vehicle of  FIGS. 1   a  and  1   b , with  FIG. 2   b  being a side view of the chassis.  FIG. 2   a  shows a complete battery  20  and a battery container  22 , the vehicle of  FIGS. 1   a  and  1   b  using two batteries for the operation thereof. The batteries  20  are aligned and slide into the vehicle on guides  24 , and when slid to their forward most position, make contact with connectors  26  fastened to the chassis. In that regard, a typical battery  20  may be seen in  FIGS. 2   c ,  2   d  and  2   e .  FIG. 2   c  is a view of a battery from the back,  FIG. 2   d  a front view of the battery and  FIG. 2   e  a side view of the battery. It will be noted that the power connector  28  within the battery, as shown in  FIG. 2   c , does not project outward from the back of the battery as may be seen in  FIG. 2   e , but rather is recessed for protection and to avoid inadvertent shorting of the battery terminals and the hazards presented thereby. At the front of the battery  20  is a handle  30 , a monitoring/recharging connector  32 , three lighting emitting diodes (LEDs)  34  and a push button switch  36 . Connector  32  in the present invention provides individual electrical connection to each cell in the battery, and further provides a serial communication link with a charger for control of the battery charging and monitoring the state of charge and health of the battery. As shall subsequently be seen, push button switch  36  may be used for checking the state of charge of the battery through LEDs  34  on the battery, even when a charger is not connected to the battery. 
       FIG. 2   f  is a perspective view of a battery charger in accordance with the present invention. The battery charger has two cables  37  for plugging into connectors  32  on two batteries  20  to charge up to two batteries at a time. The word charger as used hereafter is used in two contexts, first for a charger for an individual battery, and second, for a pair of such chargers as packaged together as in  FIG. 2   f.    
       FIG. 3  is a block diagram of the battery circuit. The particular batteries used are four cell batteries, though of course this is not a limitation of the invention. A microprocessor  38  in the battery monitors the battery cell voltage for all four cells, the first connection shown being for the battery ground, the second connection being for the first cell voltage, and then each cell voltage thereafter being measured relative to the prior cell voltage. The microprocessor also monitors battery cell temperature using a temperature sensor or similar device, and provides this information to a serial communication link  40  for communication to and from the battery through connector  32  when connected to a battery charger. The battery cell terminals themselves are also connected to connector  32 , in the embodiment shown through pins  3 ,  4 ,  5 ,  6  and  7 , with the series connection of the batteries being connected to connector  28  in the battery for supplying power to the vehicle when charged and in the vehicle. The serial communication link  40  will control an active switch  42  which will cause the microprocessor to turn on and communicate with the charger when the charger is plugged in. As shall subsequently be seen, the charger also contains three status display LEDs, duplicating the display provided by LEDs  34  on the battery. When the charger is not plugged in, the battery status may be determined by pressing switch  36 , which triggers microprocessor  38  on to power the status LEDs in accordance with the status as determined by the microprocessor. After approximately 15 to 20 seconds the microprocessor will shut off, of course turning off LEDs  34  and microprocessor  38  to save battery power. Not shown is a resistor in the battery, the resistance of which can be read by the charger over the serial communication link, the resistance being selected to indicate the battery chemistry for setting the recharging characteristics. 
     Now referring to  FIG. 4   a , which is a flow chart for the battery control on the battery, when the microprocessor is started, there is first an initialization process, and then it proceeds to read the cell voltages and the cell temperatures. It will then set the state of the LEDs (LED progress) in accordance with those readings. If a charger is plugged in, it will send that data through the serial communication link to the charger and similarly receive a data package from the charger. If a bad battery is detected (bad or excessively discharged), the status of LEDs  34  on the battery is updated (LED progress) to indicate the bad battery. 
       FIG. 4   b  is a flow chart illustrating the determination of the various battery states. For each type of battery used, a minimum voltage, an empty voltage, a half full or half charged voltage and a full or fully charged voltage for that type of battery is used. The empty voltage represents the low voltage of the battery&#39;s useful discharge cycle, the half full voltage represents a voltage at or above which the battery is considered to have a state of charge of at least 50%, and the full voltage is the voltage the battery is presumed to bed fully charged. The minimum voltage, on the other hand, is a voltage below the empty voltage, indicative not only of the discharge of the battery to below its useful voltage, but further indicative of a possible problem with the battery. Thus in the flow chart of  FIG. 4   b , all cells in the battery are tested to determine whether any are below the minimum (MIN) voltage, and if yes for any cell, the zero voltage battery flag is initiated. As shown at the top of the Figure, this is indicated on the battery LEDs by having the full and half full LEDs off and the empty LED flashing in one second intervals. If no cells are below the minimum, the cell voltages are then tested to determine if any of the cells are above the minimum voltage but less than the empty voltage. If they are, the low battery flag is initiated. This flag turns the full LED and half full LED off and the empty LED flashing, though now flashing in 100 millisecond intervals rather than one second intervals. If none of the cells are between the minimum voltage and the empty voltage, they are then tested to determine if they are between empty and half full. If yes, the full LED will be off, the half full LED will blink in half second intervals and the empty LED will be on, indicating that the battery is more than empty though less than half full. If none of the cells fall between the empty and the half full voltage, the voltage readings are then tested to determine whether any cell is between the half full and full voltage. If so, the full diode will blink in half second periods, the half full diode will be on and the empty LED will be on. Finally if none of the cells fall between half full and full, then all cells must be fully charged, and accordingly all three LEDs are turned on. Note of course in this sequence, as soon as one of the conditions has been found, the sequence stops at that point to power the LEDs accordingly. Also of course if a battery charger is connected, the serial I/O connection will report the same to the charger. Thus, for instance, if in a four cell battery, three cells are fully charged, but a weak cell is between empty and half charged, the LEDs will indicate the state of the battery as being between empty and half charged, though because the voltage of each cell will be communicated to the charger, the charger will have the information to determine which cell is the errant cell. 
     Now referring to  FIG. 5 , an overall block diagram of a battery charger in accordance with the present invention may be seen. In this diagram, only the control elements are shown, with the power elements, which may be of conventional design, being omitted for clarity. The charger is controlled by a microprocessor control board  44 . The microprocessor control board  44  controls the charger under program control by controlling the connection of the charger to the cells through relays  46 , and controlling the charging mode of each cell based on information obtained from the battery over the serial communication link. In the preferred embodiment, there are three charging modes used, identified as CC MODE  1 , CC MODE  2  and CV MODE. CC MODE  1  is a low constant current mode, 7 amps in the preferred embodiment, CC MODE  2  is a high constant current mode, 15 amps in the preferred embodiment, with CV MODE being a constant voltage charging mode representing the charging voltage limit for the 15 amp charging rate, the specific constant voltage used depending on the type (chemistry) of battery being charged. 
     Any of these three charging modes may be applied to the cells in a battery through relays  46 , though in the preferred embodiment, the same mode is applied to all cells of a battery, with the voltage of the lowest voltage cell determining the mode. In addition, the microprocessor may communicate with a battery connected to the connector  28  through the serial communication link  40 , and is configured to indicate not only that charging is in progress through LED  46  or finished through LED  48 , but also to indicate the state of charge of the battery through diodes  34 , replicating the indication on the battery itself. The charger can be activated by push button switch  52 , and once activated, will normally continue until all cells are fully charged, then disconnect the charger from the battery through relays  46  and continue to monitor the state of charge of the battery through the serial communication link. There is also an auto enable mode, wherein the charger will sense the presence of a battery on the charger, provided the battery has a sufficient voltage for serial communication with the charger. Push button switch  52  is also used to wake the battery up when the battery is very low capacity or completely drained. 
     Now referring to  FIG. 6 , part of the charger control flowchart for a charger in accordance with a preferred embodiment may be seen. Since the vehicle of  FIG. 1  uses two batteries, the charger of the preferred embodiment is also capable of charging two batteries at the same time. It is, of course, also capable of charging only a single battery at a time, which may be connected to either port of the charger. When power is supplied to the charger (START), the charger goes through an initialization process and then sends a request for data to the first battery connection. If there is no battery connected to that charger connection, or alternatively the battery that is connected is too dead to reply, the charger for that battery is disabled. If a reply is received from the battery, the LEDs on that charger and battery are updated to indicate that the battery is being charged and the present state of charge of the battery, and the charger is then enabled with the logic flow then proceeding as identified as sequence  1  ( FIG. 7 ). Whether or not the charger for battery  1  was enabled, the charger then goes through the same process for battery  2 . Note that in either case, if no battery is connected to the charger, or alternatively the battery is too dead to respond, the charger for that battery will believe no battery is connected and accordingly will not begin the charging sequence. The charger will also check to see if either charger, Charger  1  for the first battery or Charger  2  for the second battery, has been turned on by control switches on the battery charger (charger # 1  enable pushbutton and charger # 2  enable pushbutton). If the switch for either battery has been turned on, the respective charger is enabled and another serial communication with the battery is attempted. If a battery is connected, the charger will sense the presence of the battery by sensing the charger current. Given a battery present, the charger will then go to sequence  1  or sequence  2 , or both, to charge one or both batteries. As long as the charger itself has power, it will repeat the test to sense when a battery is connected to the charger, if not too dead, or when a charger is manually turned on. As described, sequence  1  and sequence  2  are identical sequences and accordingly only sequence  1  will be described herein in detail. 
     Sequence  1  (and/or sequence  2 ) begins with a communication from the battery of the battery cell voltages and temperatures as well as battery type, which the charger then uses to update the LEDs on the charger to indicate that status. Even if the communication with the battery is unsuccessful, the charger proceeds with sequence  1 . The cells of the battery are tested to see if any cell is above the maximum temperature allowed, and if so, the charger is disabled and a bad battery is flagged. If not, the cells of the battery are then tested to see if any cell is below the minimum charge, and if yes, the charger is enabled and set to the CC mode  1  (7 amps) to charge the cells for 10 minutes, after which the cells are again tested to determine if any cell is below the minimum charge. The 10 minutes should be adequate to bring the voltage of any properly operating cell to above the minimum voltage. If it doesn&#39;t, the charger is disabled and the bad battery flag activated. If none of the cells are below the minimum voltage, or at least are no longer below the minimum voltage after the 10 minutes, the charger is set to CC mode  2  and the maximum timer set to a time more than adequate to charge a properly functioning battery. The LEDs are updated and the charger signals checked. If the check signal indicates 1) an alarm signal (overheating), 2) a working signal at zero volts (charger fault), 3) a cell temperature above the maximum allowable temperature, or 4) over voltage charging above the maximum allowable voltage (charger fault), the charger is disabled and a bad charger flag is activated. If over voltage charging occurs, the charger is latched in the disable mode until the charger is recycled through the AC switch. Otherwise the LEDs will be continually updated, either until the battery is fully charged or the maximum timer times out. Of course the CC mode  2  will charge the cells at 15 amps, but will reduce the charging rates as each cell reaches the CV mode. Once all cells are fully charged or the timer has timed out, the battery is allowed to sit without charging for 10 minutes to stabilize, within which time a faulty cell will show itself by an extraordinarily high self discharge rate. During the 10 minutes, the LEDs indicating the state of the battery charge are updated, with the charger being disabled at the end of the 10 minutes and going into an auto enable mode. During the entire charging process, the cell temperatures are monitored, and if the temperature of any cell exceeds the maximum allowed, the charger is disabled and a bad battery flagged. 
     The auto enable mode is shown in  FIG. 8 . In the auto enable mode the charger will periodically test any cell to see if its voltage has fallen below 3 volts. If it has not, it will disable the charger and update the status of the LEDs on the charger to turn on the complete charge LED. If the voltage on a cell has fallen below 3 volts (depending on battery chemistry), the charger for that battery is then turned on and the charger returns to sequence  1  or  2 , identical sequences with sequence  1  being shown in  FIG. 7 . 
     As shown in  FIG. 5 , charger # 1  has five LEDs (for each battery and charger) to indicate charger and battery status. LED  48  on indicates that the battery is being charged, and LED  50  on indicates the battery is fully charged. A bad battery is flagged by all of LEDs  34  flashing. A bad charger (over heat and over voltage) is flagged by LEDs  48  and  50  flashing. The LEDs  34 , full half and empty) are used to indicate any of four battery states of charge for batteries not flagged as bad. These states of charge, duplicated by the LEDs on the battery itself, and sensed by cell voltages, are battery full (fully charged), between half full and full, between empty and half full, and between a minimum voltage and empty. Below the minimum voltage the battery is flagged as a bad battery. Empty means that the battery has reached its defined useful state of discharge and should be recharged. Between the minimum voltage and empty, the state of charge is flagged by the full and half LEDs  34  being off and the empty LED flashing. Between the empty and half full, the state of charge is flagged by the full LED  34  being off, the half LED flashing and the empty LED being on. Between the half full and full, the state of charge is flagged by the full LED  34  flashing and the half and empty LEDs being on. When full, all three LEDs  34  will be turned on. As shown in  FIG. 5 , charger # 2  is the same configuration as charger # 1 . Charger # 1  and charger # 2  are independently controlled by the microprocessor. 
     In a specific example disclosed herein, the battery is a four rechargeable cell battery, and thus the battery charger accommodates the charging of four cells per battery. Of course the batteries and chargers in accordance with the present invention may also be configured for more or less cells, as desired. 
     The present invention, the preferred embodiment of which has been described, has a number of aspects, which aspects may be practiced alone or in various combinations or sub-combinations, as desired. While a preferred embodiment of the present invention has been disclosed and described herein for purposes of illustration and not for purposes of limitation, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the full breadth of the following claims.