Electrolyte circulation type secondary battery operating method

A method of operating a secondary battery including a stack of secondary cells operable, in the presence of electrolytes, in a charge mode charging electrical power from a source of electrical power and in a discharge mode discharging the charged electrical power, and electrolyte circulating means electrically operable for circulating the electrolytes through the secondary cells, the method comprising the steps of:

• in the charge mode,
• providing an approximate indication of electrolyte condition by measuring a voltage across the terminals of the secondary battery;
• comparing the measured secondary battery voltage with a first and second predetermined value, the second predetermined value being less than the first predetermined value;
• electrically connecting the electrolyte circulating means to the electrical power source to start circulation of the electrolytes through the secondary cells when the secondary battery voltage increases to the first predetermined value;
• disconnecting the electrolyte circulating means from the electrical power source to stop the electrolyte circulation when the secondary battery voltage decreases to the second predetermined value;
• and thereafter
• while the secondary battery is operating in the charge mode, continuously repeating the above sequence of steps to intermittently circulate the electrolytes through the secondary cells;
• in the discharge mode,
• providing an approximate indication of electrolyte condition by measuring a voltage across the terminals of the secondary battery;
• comparing the measured secondary battery voltage with a third and fourth predetermined value, the fourth predetermined value being greater than the third predetermined value;
• electrically connecting the electrolyte circulating means to the secondary battery to start circulation of the electrolytes through the secondary cells when the secondary battery voltage decreases to the third predetermined value;
• disconnecting the electrolyte circulating means from the secondary battery to stop the electrolyte circulation when the secondary battery voltage increases to the fourth predetermined value;
• and thereafter
• while the secondary battery is operating in the discharge mode, continuously repeating the above sequence of steps to intermittently circulate the electrolytes through the secondary cells.