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Method and apparatus for exporting power in a renewable energy system employing a battery charger

  • US 8,076,907 B2
  • Filed: 08/06/2008
  • Issued: 12/13/2011
  • Est. Priority Date: 08/06/2008
  • Status: Active Grant
First Claim
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1. A method of charging a battery in a system comprising a renewable energy source and operable to supply at least some electrical energy from the renewable energy source to a third party, the method comprising:

  • causing a charge controller operably connected to said renewable energy source to receive said electrical energy from said renewable energy source and operably connected to the battery, to charge the battery, using only said electrical energy from the renewable energy source, according to a charging sequence comprising at least;

    a bulk charge period wherein the battery is charged at a relatively constant charging current;

    an absorption period following said bulk charge period wherein the battery is charged in an absorption mode; and

    a float period following said absorption period wherein the battery is charged in a float charging mode;

    producing a charger current value representing current supplied by the charge controller;

    producing a battery voltage value representing a battery voltage;

    causing said charge controller to transmit an indication of the current period of said charging sequence and a reference voltage value associated with the current period of said charging sequence, to an inverter operably connected to the charge controller and the battery to receive electrical energy therefrom;

    causing said inverter to draw current from the charge controller to supply electrical energy to the third party, without drawing sufficient current to load the charge controller to a point where said battery voltage value drops below a target voltage dependent on said reference voltage value, when said charge controller indicates said absorption period or said float period is in progress;

    causing said charge controller to set said indication of the current period of said charging sequence to indicate that the current period of said charging sequence is the absorption period and causing said charge controller to set said reference voltage to correspond to an absorption voltage of said battery, when said battery voltage value meets a bulk charge exit criterion;

    producing an inverter current value representing the current drawn by the inverter;

    transmitting said inverter current value to said charge controller; and

    causing said charge controller to set said indication of the current period of said charging sequence to indicate that the current period of said charging sequence is the float period and causing said charge controller to set said reference voltage to correspond to a float voltage of said battery less than said absorption voltage of said battery, when said charger current value and said inverter current value meet absorption period exit criteria.

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