Intermittent refilling of print cartridge installed in an inkjet printer

A method for refilling a refillable print cartridge, said print cartridge having a print cartridge body containing a first ink reservoir having been initially filled with ink supplied through a first ink fill port in said print cartridge body, said first ink fill port being sealed with a first seal, said method comprising:

• removably mounting said print cartridge on a carriage in a printer;
• providing an external ink reservoir containing ink, separate from said print cartridge;
• coupling said external ink reservoir to a recharge port on said body, said recharge port being separate from said first ink fill port and being sealed with a second seal which is in an opened state or a closed state, said closed state providing a fluid seal of said first ink reservoir, said opened state providing fluid communication between said external ink reservoir and said first ink reservoir when said external ink reservoir is connected to said recharge port, said second seal allowing no ambient air to enter said first ink reservoir when in fluid communication with said external ink reservoir;
• operating said printer incorporating said print cartridge so as to print ink on a medium from a quantity of ink in said first ink reservoir;
• recharging said first reservoir, when a supply of ink in said first ink reservoir is at least partially depleted, by:
• a) creating a negative pressure, relative to atmospheric pressure, in said first ink reservoir after said supply of ink in said first ink reservoir has been at least partially depleted;
• and
• b) supplying ink at only predetermined times from said external ink reservoir to said first ink reservoir via a transfer tube connected between said external ink reservoir and said first ink reservoir.