One way to save money on those expensive ink cartridges is to refill them when they are empty instead of buying a new cartridge. However, if the cartridges are for a Hewlett-Packard printer, there's an additional issue. HP printers recognise when a cartridge is empty, but do not recognise a refilled cartridge as being filled, which means it will not allow that refilled cartridge to be used for printing. Removing the printer's battery for a short period can reset the printer, allowing it to recognise refilled cartridges as new cartridges ready for printing.
Unplug the printer's power cord, and unplug the cord connecting the printer to the computer. This ensures the printer is off and disconnected before removing the battery.
Open the top of the printer, taking care not to scratch or otherwise damage any of the internal pieces.
Locate the battery inside the printer. Its location varies depending on the model of HP printer, but generally it is located in the front lower left section of the printer. It should resemble a small silver disc.
Unplug the battery from the printer by unplugging the small cable attached to it.
Wait about an hour. Reconnect the battery to the printer. After reconnecting the printer to a power outlet and the computer, it should start and recognise a refilled ink cartridge as new.
Consult the user manual for the specific HP printer model to determine the precise location of the printer battery, as it can vary from model to model.
Exercise caution when dealing with the internal components of the printer. Do not unplug or otherwise remove anything unless you are certain it is the piece you want. Do not do anything that cannot be reversed easily.