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

An apparatus for 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 apparatus comprising:

• charging means for charging the battery, using only said electrical energy from the renewable energy source, according to a charging sequence, wherein said charging means is 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, and said charging sequence comprises 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;
• means for producing a charger current value representing current supplied by the charging means to the battery;
• means for producing a battery voltage value representing a battery voltage;
• and
• receiving means operably connected to the charging means and the battery for receiving electrical energy therefrom;
• wherein said charging means is operably configured 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 said receiving means;
• wherein said receiving means is operably configured to:
• receive current from said charging means to supply electrical energy to the third party, without drawing sufficient current to load the charging means to a point where said battery voltage value drops below a target voltage dependent on said reference voltage value, when said charging means indicates said absorption period or said float period is in progress;
• and
• transmit to said charging means a received current value representing the current received by the receiving means;
• and
• wherein said charging means is operably configured 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 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;
• and
• 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 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 received current value meet absorption period exit criteria.

An apparatus for 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 apparatus comprising:

• a charge controller for charging the battery, using only said electrical energy from the renewable energy source, according to a charging sequence, wherein said charge controller is 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, and said charging sequence comprises 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;
• a current measuring device in communication with said charge controller and operably configured to produce a charger current value representing current supplied by the charge controller to the battery;
• a voltage measuring device in communication with said charge controller and operably configured to produce a battery voltage value representing a battery voltage;
• and
• an inverter operably connected to the charge controller and the battery for receiving electrical energy therefrom, and in communication with said charge controller and said voltage measuring device to receive said battery voltage value therefrom;
• wherein said charge controller includes a first transmitter operably configured 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 said inverter;
• wherein said inverter is operably configured to receive current from said 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;
• wherein said inverter includes a second transmitter operably configured to transmit to said charge controller an inverter current value representing the current received by the inverter;
• and
• wherein said charge controller is operably configured 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 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;
• and
• 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 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.

A method of charging at least one battery in a system comprising at least one renewable energy source and operable to supply at least some electrical energy from said at least one renewable energy source to a third party, the method comprising:

• associating charge controllers and inverters of said system into groups and associating said groups with at least one respective battery, wherein each group comprises at least one charge controller and at least one inverter, and wherein each said charge controller is operably connected to said renewable energy source to receive said electrical energy from said renewable energy source and operably connected to the at least one associated battery, to charge the at least one associated battery, using only said electrical energy from the renewable energy source, and wherein each said inverter is operably connected to at least one said charge controller in a same group and to the at least one associated battery to receive electrical energy therefrom;
• causing all of the charge controllers and inverters in each group to communicate with other charge controllers and inverters in the same group;
• causing one charge controller in the group to be identified as a group primary charge controller;
• causing each of said at least one charge controller in a common group to:
• produce a charger current value representing current supplied by that charge controller;
• produce a battery voltage value representing the voltage of said at least one battery associated with said common group;
• and
• transmit said charger current value and said battery voltage value to said group primary charge controller of said common group;
• causing said at least one charge controller in said common group to supply a battery charging current to said at least one battery associated with said common group, according to a charging sequence associated with said common group, said charging sequence comprising at least:
• a bulk charge period wherein said at least one battery associated with said common group is charged at a relatively constant charging current;
• an absorption period following said bulk charge period wherein said at least one battery associated with said common group is charged in an absorption charging mode;
• and
• a float period following said absorption period wherein said at least one battery associated with said common group is charged in a float charging mode;
• causing said group primary charge controller of said common group to transmit an indication of the current period of said charging sequence associated with said common group and a reference voltage associated with the current period of said charging sequence associated with said common group, to said at least one inverter in said common group;
• when said group primary charge controller of said common group indicates said absorption period or said float period is in effect, causing each of said at least one inverter in said common group to:
• measure a battery voltage value of said at least one battery associated with said common group;
• draw current from the at least one charge controller in said common group without drawing sufficient current to load the at least one charge controller of said common group to a point where said battery voltage value measured by that inverter drops below a target voltage dependent on said reference voltage associated with the current period of said charging sequence associated with said common group, wherein said current drawn from the at least one charge controller in said common group is provided to the third party;
• measure the current drawn by that inverter;
• and
• transmit to said group primary charge controller of said common group, an inverter current value representing current drawn by that inverter;
• causing said group primary charge controller of said common group to set said indication of the current period of said charging sequence associated with said common group to indicate that the current period of said charging sequence associated with said common group is the absorption period;
• causing said group primary charge controller of said common group to set said reference voltage associated with the current period of said charging sequence associated with said common group to correspond to an absorption voltage of said at least one battery associated with said common group, when at least one of said charge controllers in said common group transmits to said group primary charge controller of said common group a battery voltage value that meets a bulk period exit criterion;
• and
• causing said group primary charge controller of said common group to set said indication of the current period of said charging sequence associated with said common group to indicate that the current period of said charging sequence associated with said common group is the float period and causing said group primary charge controller of said common group to set said reference voltage associated with the current period of said charging sequence associated with said common group to correspond to a float voltage of said at least one battery associated with said common group, said float voltage of said at least one battery associated with said common group being less than said absorption voltage of said at least one battery associated with said common group, when said charger current values of said at least one charge controller of said common group and said inverter current values of said at least one inverter of said common group meet absorption period exit criteria.