While Nissan has upgraded the LEAF’s battery pack in its latest version with now a 30 kWh option, the low energy capacity of the vehicle is still a major factor dragging it down. Potential buyers would like to see better options with more range.

Nissan engineers actually built a LEAF with a bigger battery pack, but unfortunately, it is not intended for production and was built during their spare time.

The automaker said in a press release that a group of technicians at Nissan’s Technical Centre in Barcelona (NTCE-S) built the vehicle as a passion project. The new battery pack has a 48 kWh capacity and offers a range of about 147 miles on a single charge.

The company wrote in the press release:

In a demonstration of their passion for innovation, Nissan engineers have created a prototype Nissan LEAF with a 48 kWh battery in their spare time.

Following the manufacturer’s principles of on-going research and development of electric vehicles, the 48 kWh prototype carries a battery twice the size of the original Nissan LEAF production model, with a 75% increase in driving range in everyday conditions.

It was created by a group of technicians at Nissan’s Technical Centre in Barcelona (NTCE-S), whose passion and commitment to their work has given rise to the Nissan Innovation team. The team of volunteers take on a range of exciting endeavours, pushing the boundaries of what is possible with electric vehicle technology.

The prototype, codenamed ‘Cocoon’ in reference to the American sci-fi film of the same name, was built to compete in the Spanish motorsport event, ECOseries – a new initiative which rewards ‘efficiency and fuel economy rather than outright speed’

The next battery pack upgrade expected to make it in the LEAF is actually a 60 kWh pack. Some are expecting it as soon as next year to compete with the Chevy Bolt and Tesla Model 3, but the automaker has yet to confirm the introduction of the new update.

Here’s Cocoon:

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