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Nissan Leaf battery  (Source: gas2.org)
The home charges the Leaf battery, and eventually, the stored electricity in the battery can be used to charge the home in the event of a blackout

Just last month, Nissan was looking for ways to utilize the battery packs inside of its Leaf EV once the vehicle has reached the end of its lifespan. The automaker found that these batteries will still have 80 percent of their original charge capacity once the Leaf is ready to be laid to rest, and with its plans to release seven EV models (in addition to the Leaf) by 2016, that will be a lot of leftover batteries.

Nissan found that using these batteries as energy storage devices made the most sense. In fact, the company kept four old Leaf batteries in a cellar in a Nissan building, and the batteries were hooked up to 488 solar panels on the roof. This allows the batteries to store the energy that these solar panels create, and the power produced is enough to charge 1,800 Leaf vehicles annually.

Now, Nissan is introducing another similar initiative called "Leaf-to-Home," which will use electricity stored in Leaf batteries to be distributed to residential homes and appliances. The new plan serves as a two-way charging system, meaning that the Leaf can be charged as usual, but the Leaf can eventually return the favor by supplying electricity from its battery when there's a local power outage.

The system is currently being tested in Japan, since March's 9.0-magnitude earthquake caused an energy shortage. The Leaf's 24 kilowatt hour (kWh) battery is capable of powering a Japanese home for two days.

An American home, on the other hand, may not benefit quite as much from such a system due to the fact that the average U.S. home uses 908 kWh electricity per month, which equates to 30 kWh per day. According to recent reports, the Leaf battery would barely charge an American household for a day at full charge. However, it could be useful for a local brown-out. 

Nissan hopes to be able to sell a commercial version of the "Leaf-to-Home" next year in Japan.



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RE: Profit
By EddyKilowatt on 8/3/2011 6:32:18 PM , Rating: 2
Li-Ion charge efficiency is quite good at 97-99%, they're remarkably cool-running batteries actually (http://batteryuniversity.com/learn/article/chargin... A well-designed inverter has similar efficiency. So, energy losses won't kill your profits.

Loss of cycle life might affect the balance sheet, though. Li-Ion is cost-effective on a cycle life basis when powering a vehicle and competing with IC engine fuel and maintenance cost, but probably not when just storing bulk energy and earning utility buyback rates... they'd cost more per cycle to operate than you'd earn arbitraging the night/day power differential.

Electric cars do look pretty exciting as a distributed power source for grid stabilization... this would only use a few percent of the battery capacity and have very little effect on cycle life.


RE: Profit
By Starcub on 8/4/2011 5:22:17 PM , Rating: 2
It might not be cost effective to buy the battery specifically for that purpose, but if you own a Leaf then the cost of the battery is essentially nothing. You might as well use it to power you home, or sell power back to the utility co.

Judging from the article and the Nissan program, it would seem that these l-ion batteries are much more robust than your typical laptop l-ion batteries. Laptop batteries typically become useless after about 5 years, and not on a linear curve. When l-ion laptop batteries hit 80% initial capacity the life cycle power curve drops sharply. Evidently the story is different with the leaf battery.

I would think that using the battery in this fashion would affect the resale value of the car. However, a prospective buyer might want or expect to get a new battery anyway.


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