The Castagna Milano's Mini Cooper hybrid conversion retains much of the orginal engine. They strengthen the suspension system and fit an electic motor to the rear of the vehicle. This allows the driver to switch to all electric with a switch on the dashboard whenever he wants.
The batteries are guaranteed for a period of 5 years and they can be fully charged in 6 hours through a domestic power outlet.
The real problem is the cost:
The cost for the conversion is about 40,000 euros plus the cost of the Mini. Unfortunately they have to do the stretch to have the space for the batteries and that alone costs 19,500 euros. So the hybrid part costs 20,000, of which they say 11,000 is for the battery pack.
Based on the current conversion rate of Euros to dollars, that's more than $48,000 for the conversion and more than $13,000 for the ZEBRA battery.
I saw this story at evworld being quoted at autospies.