Recently bought a second hand BMW i3 - what a cool car! Not planning to 'hack' it but nice to read about ideas.
This is the kind of hacking / upgrades I’d love to see. All in cost was about $6k when I last checked probably a little more now. You get a pack teardown, and new CATL cells. Range goes to 400km~.
Later models, 120ah full electric version, the range is about 250km. In comparison to newer cars, not a lot, but considering you can buy newish used ones for under 15k, its not a bad deal if it fits your needs.
If I was in it for the karma I'd be in the billions by now.
As for the range, I'm getting about 110 miles of range. It depends how you drive. This is the 94Ah battery, the later models had more range.
It also came in handy for a bad road trip (charging stations more than my range apart, so I couldn’t otherwise get there from here, but hold state of charge kept it up at 75% with frequent gas stops)
It was either 1.9 or 2.4 gallons depending on the model year, but they physically had the same gas tank.