> 'smart carts'. It looks like they simply have an nvram on the cart

Wouldn't be hard to bury an SMT IC in the case. But how would
the printer know that it was a refill ? Something must happen in
the refilling process to change the cartridge

I helped a friend defeat his Xerox (I think) copier that had a page
counter. It would stop when the "recommended" number of pages
had been printed using the current cartridge, even if there was still
oodles of toner left. The hack was to simply zero the page-counting
EEPROM in the copier. Eventually the toner would run out but he
was happy enough to get that 30% "extra" that he'd paid for

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