Abstract:
A solar power management system includes a plurality of photovoltaic cell panels, and a solar power cell manager coupled to the photovoltaic cell panels. The solar power cell manager includes an input stage for combining current draws from the photovoltaic cells, and a load manager in communication with the input stage for managing the combined current draw.

Description:
FIELD OF THE INVENTION 
     The preset invention relates to a system for delivering solar power to a load. In particular, the present invention relates to a solar power management system for interfacing a rechargeable battery to a plurality of photovoltaic cell panels. 
     BACKGROUND OF THE INVENTION 
     The conventional solar power management system consists of a plurality of photovoltaic cell panels, a combiner box for interconnecting the photovoltaic cell panels, and a charge controller box connected to the combiner box for controlling the current delivered by the photovoltaic cell panels to a rechargeable battery. Typically, the combiner box and charge controller are used to interface the photovoltaic cell panels with a lead-acid battery or other rechargeable battery, although other loads are also possible. 
     Although the conventional solar power management system is satisfactory for charging a rechargeable battery over several hours, care must be taken to ensure that the photovoltaic cell panels are connected to the combiner box with the correct polarity to prevent one of the panels from negating the power delivered from the other panels. Also, a short in any of the panels can short out the remaining photovoltaic cell panels. Therefore, there remains a need for a solar power management system which prevents current from being delivered to the load when one of the photovoltaic cell panels fails or is connected with the incorrect polarity. 
     SUMMARY OF THE INVENTION 
     According to the invention, there is provided a solar power management system and a solar power cell manager which addresses at least one deficiency of the prior art. 
     The solar power management system, according to the present invention, includes a plurality of photovoltaic cell panels, and a solar power cell manager coupled to the photovoltaic cell panels. The solar power cell manager includes an input stage for combining current draws from the photovoltaic cells, and a load manager in communication with the input stage for managing the combined current draw. 
     The solar power cell manager, according to the present invention, includes an input stage for interfacing with a plurality of photovoltaic cell panels, and a load manager in communication with the input stage for controlling current flow between the photovoltaic cell panels and a load. 
     In the preferred implementation, the solar power cell manager includes a housing, and an input stage and a load manager disposed within the housing. The input stage electrically isolates the photovoltaic cell panels from one another so that operation of the photovoltaic cell panels will not be detrimentally affected if one of the photovoltaic cell panels develops a short or is connected to the solar power cell manager with the incorrect polarity. In addition, the input stage includes a plurality of indicator lamps, each associated with a respective photovoltaic cell panel, to provide a visual indication of whether the associated photovoltaic cell panel is connected to the solar power cell manager with the correct polarity. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
     FIG. 1 is a perspective view of the solar power management system, according to the present invention, showing the photovoltaic cell panels, the load, and the solar power cell manager; 
     FIG. 2 is a schematic diagram of the input stage and the load manager of the solar power cell manager shown in FIG. 1; and 
     FIG. 3 is a plan view of the status display panel of the solar power cell manager. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning to FIG. 1, a solar power management system, denoted generally as  100 , is shown comprising a plurality of photovoltaic cell panels  102 , a load  104 , and a solar power cell manager  106  coupled to the photovoltaic cell panels  102  for interfacing the photovoltaic cell panels  102  with a load  104 . Preferred photovoltaic cell panels  102  include Unisolar US32 or Kyocera KC50 solar panels. Also, typically the load  104  comprises a rechargeable battery, although the load  104  may also comprise other types of loads such as DC-AC inverters. 
     The solar power cell manager  106  includes a housing  108 , an input stage  110  and a load manager  112  disposed within the housing  108 , and a status display panel  114  provided on an external upper surface of the housing. AS shown in FIG. 2, the input stage  110  includes a plurality of input ports  116  each interfacing with a respective photovoltaic cell panel  102 , a positive output voltage bus  118   a  and a negative output voltage bus  118   b  for providing DC power to the load manager  112 , and a plurality of separate and distinct interface stages  120  each coupled to a respective input port  116  for conveying current produced by the photovoltaic cell panels  102  to the output bus  118 . 
     As will be apparent, the interface stages  120  are isolated from one another so that operation of the photovoltaic cell panels  102  will not be detrimentally affected if one of the photovoltaic cell panels  102  develops a short or is connected to the solar power cell manager  106  with the incorrect polarity. Preferably, the input ports  116  extend through the upper surface of housing  108  in proximity to the status display panel  114  to allow the photovoltaic cell panels  102  to be easily connected to the solar power cell manager  106 . 
     Each interface stage  120  includes a unidirectional current flow controller  122  in series with the respective input port  116  and in parallel with the output bus  118 , and a power sense stage  124  in parallel with the unidirectional current flow controller  122 . The unidirectional current flow controller  122  is provided to prevent one of the photovoltaic cell panels  102 , connected to the solar power cell manager  106  with the incorrect polarity, from shorting out another of the photovoltaic cell panels  102 , connected to the solar power cell manager  106  with the correct (ie. opposite) polarity. As shown, preferably the unidirectional current flow controller  122  comprises a semiconductor diode, however it will be appreciated that other devices, such as diode-connected transistors, may be used as the unidirectional current flow controller  122  instead of a semiconductor diode. 
     The power sense stage  124  provides a visual indication of whether the associated photovoltaic cell panel  102  is connected to the solar power cell manager  106  with the correct polarity and is providing the solar power cell manager  106  (and the load  104  if connected) with power. As shown, preferably the power sense stage  124  comprises a series circuit of a light emitting diode (LED)  126 , a sener diode  128 , a current limiting resistor  130  and a blocking diode  132 , although other circuit configurations for the power sense stage  122  may be provided without departing from the scope of the invention. 
     The zener diode  128  limits current flow through the LED  126  until the voltage produced by the associated photovoltaic cell panel  102  reaches a minimum threshold level and, therefore, prevents the LED  126  from illuminating if the voltage produced by the photovoltaic cell panel  102  is less than the minimum threshold level. As will be apparent, the zener diode  128  may be eliminated from the power sense stage  124  if LED illumination control is not a significant concern. 
     The blocking diode  132  serves to control the current through the LED  126  (in conjunction with the current limiting resistor  130 ) and also prevents the LED  126  from illuminating when the associated photovoltaic cell panel  102  is connected to the solar power cell manager  106  with the incorrect polarity. As will be apparent, as the LED  126  is itself a diode, the signal diode  132  may be eliminated if the photovoltaic cell panels  102  do not produce a significantly large voltage. However, as typical LEDs do not have particularly good reverse voltage ratings, in many applications some reverse voltage blocking circuit element will be desired. 
     As shown in FIG. 3, the LEDs  126  extend through the upper surface of the housing  108  and form part of the status display panel  114  so as to be visible to a user of the solar power cell manager  106 . In addition to the LEDs  126 , the status display panel  114  includes a battery charging indicator lamp  134  to provide a visual indication that a rechargeable battery is connected to the solar power cell manager  106 , and first, second and third battery voltage level indicator lamps  136   a ,  136   b ,  136   c  to provide a visual indication of the voltage level of the rechargeable battery. Preferably, the first battery voltage indicator lamp  136   a  is a green coloured lamp, the second battery voltage indicator lamp  136   b  is a yellow coloured lamp, the third battery voltage indicator lamp  136   c  is a red coloured lamp. However, the indicator lamps  136  may be replaced with a single multicoloured LED, if desired. 
     The load manager  112  is in communication with the input stage  110  via the output bus  118 , and comprises a current controller  138 , a pair of battery charging terminals  140   a ,  140   b  for interfacing with a rechargeable battery, and a pair of load terminals  142   a ,  142   b  for interfacing with an external load (such as a DC-AC inverter). Preferably, the terminals  140 ,  142  extend through the upper surface of housing  108  in proximity to the status display panel  114  to allow the rechargeable battery and/or the external load to be easily connected to the solar power cell manager  106 . 
     The load manager  112  is configured to control the current flow from the photovoltaic cell panels  102  to the external load and/or a 12 volt rechargeable battery. Further, the current manager  112  interfaces with the status display panel  114  and controls the charging indicator lamp  134  and the voltage indicator lamps  136 . Preferably, the load manager  112  is configured to: 
     (1) cause the first (green) voltage indicator lamp  136   a  to blink when the rechargeable battery holds a full charge; 
     (2) continuously illuminate the first (green) voltage indicator lamp  136   a  when the charge held by the rechareable battery is at least 70% of the full charge; 
     (3) continuously illuminate the second (yellow) voltage indicator lamp  136   b  when the charge held by the rechargeable battery is at between 30% and 70% of the full charge; 
     (4) cause the third (red) voltage indicator lamp  136   c  to blink when the charge held by the rechargeable battery is less than 30% of the full charge; and 
     (5) continuously illuminate the third (red) voltage indicator lamp  136   c  when the rechargeable battery is not connected to the solar power cell manager  106 . 
     A suitable load manager  112  for the purposes disclosed herein is the Morningstar charge controller, as described in U.S. Pat. No. 5,635,816, the entire contents of which are incorporated herein by reference. 
     The present invention is defined by the claimed appended hereto, with the foregoing description being illustrative of the preferred embodiment of the present invention. Those of ordinary skill may envisage certain additions, deletions and/or modifications to the described embodiment which, although not explicitly suggested herein, do not depart from the spirit or scope of the present invention, as defined by the appended claims.