Enginer can install variable sizes of lithium-ion batteries at the bottom of the Leaf's trunk, either 4- 8- or 12-kWh. That top-end pack is about half the size of the standard Leaf's pack, and would boost the Leaf's current official range of 73 miles to over 110. The extra pack can charge the car's original pack while driving and draws a charge through the standard charger.
The most powerful system costs almost $7,500, including installation, but Green Car Reports describes that process as "lengthy and complicated." Whether this aftermarket option will become somewhat redundant next year remains in question because of reports that the 2013 model-year Leaf could have a single-charge range of up to 90 miles.
In 2009, Enginer was offering add-on plug-in packs for the Toyota Prius, a 2-kWh model for $1,995 or $2,995 for a 4-kWh pack (plus installation and delivery).