EV batteries evergreen

Energizer bunnies, read this and weep. According to Nissan, the battery pack in its LEAF hatches is likely to outlast the rest of the car, with individual cells giving up to 20 years' service before being broken down.

It takes a lot of electrical energy to punt a car, its occupants and their luggage around at normal car speeds. That’s why EVs need such big batteries – and even then, we’re still looking at substantial limitations on how far they can take us compared to what we’re used to with a combustion engine. Thus EVs have to run with exceptionally high levels of efficiency – much higher than any other autonomous electrical device (that is, not plugged into the grid as it runs).

That means EV batteries need to be discarded when there’s still plenty of capacity – read: usability – left in them. This is an important consideration in the design of EV battery packs. They’re not split into multiple cells only because they work more efficiently that way.

The modularity is also to help find them an afterlife, Nissan executive Francois Bancon explained at the recent local launch of the company’s LEAF EV.

“We can easily imagine a second life for the [LEAF] battery,” he told motoring.com.au.

Bancon says Nissan envisages an average life of about eight years for the battery bought with the car. Indeed, the company is confident enough of that to put an eight-year/160,000km warranty on the power pack.

“We think, after average use over that time, its capacity will be down to about 60 per cent. That’s somewhere down round the usability borderline for the car – time for a changeover.”

But the battery remains a long way from landfill.

“After it comes out of the car, there are a lot of people who need energy for applications that don’t require the same levels of efficiency. Hospitals are a natural place for them – they have many relatively static applications that don’t place the same demands on the cells as the car does, [such as] ECT and imaging machines, particularly portable ones.

"The [individual] cells will still be perfectly useful for them for a long time afterwards,” Mr Bancon said.

The second life will often be longer than the first life, he said.

“All up, we’re looking at a 15-20 year lifespan for it. There’s no big limitation on it because there are no mechanical components in a battery. That means a long life with just a little maintenance, chemical maintenance.”

Mr Bancon said Nissan is working on residual value estimates as high as 50 per cent at the changeover point. It should come as no surprise that details are scant on how that value might be distributed between maker and buyer – stakeholders are a long way from having to worry about it at this point, and a lot will likely change in the time it takes before LEAF owners have to think about it.

“But we can translate this into a lot of business that will help cut the cost of the battery for [car] owners,” Mr Bancon said.

The LEAF’s battery is made by Automotive Energy Supply Corporation (AESC), a concern owned 51:49 by Nissan and electronics giant NEC respectively.

“The battery is about 25-30 per cent of the cost of an EV, so it was critical for us to set up our EV business model with the engineering and manufacture of our own batteries as a core element. The best way to do that was to start up a separate organisation to work up all the necessary partnerships for aspects of the business like charging and recyclability,” Mr Bancon stated.

AESC developed the battery from scratch to be dismantled and refurbished, with discarded cells put to use in other ways.

“That’s part of the game,” Mr Bancon said. “We have lot of partners helping us do this, in addition to our own design centre.”

The LEAF power pack’s 192 laminated lithium-ion cells are divided into four 48-cell modules. Towards the end of its life, some of those cells are remain unaffected, Mr Bancon said

“But the others, yes, they can be replaced with full-efficiency units in the car, then sent off for other duties.

“Recyclability is a critical part of the whole thing – extracting everything we can," he commented.

Read the latest news and reviews on your mobile, iPhone or PDA at carsales' mobile site…