When your plug-in hybrid or electric vehicle is ready for the recycling center, the costly lithium-ion battery that makes it go isn’t ready to be ripped apart into its essential elements. Now GM and ABB have shown you can turn the old batteries into uninterruptible power supplies that keep a house going for a couple days. The trick: Your iPhone or laptop battery is a goner after a couple hundred discharge-recharge cycles, but after a decade of use a car’s lithium-ion battery still holds at least 70% of the power it had on day one.

General Motors and Swiss power-and-automation giant ABB created a prototype module from five used Chevrolet Volt batteries at the recent GM Electrification Experience in San Francisco. The unit output 25 kW of power and 25 kWh of energy. There it ran lighting and AV equipment in an off-grid structure used at the event. In a real situation — as real as a metal skid with used Chevy Volt batteries on your street would be “real” — GM says it would provide two hours of electricity for three to five typical American homes.

Pablo Valencia, GM senior manager of battery lifecycle management said, “In many cases, when an EV battery has reached the end of its life in an automotive application, only 30 percent or less of its life has been used. This leaves a tremendous amount of life that can be applied to other applications like powering a structure before the battery is recycled.”

The modular unit would include not just the batteries but charging transformers, switches that kick in when the power fails, and metering so one house doesn’t take more than its fair share of energy. At each house, there would have to be manual or automatic transfer switches and load-shedding, meaning a hierarchy of which fixtures get the power: the sump pump and the heart lung machine before the refrigerator, the refrigerator before a curling iron.

Why it’s possible: EV batteries lead a soft life

The big battery packs in hybrids, PHEVs, and EVs have to put out huge amounts of power. What most people don’t know is that the recharge-discharge cycle is engineered so the battery will effectively never wear out. That’s not the case with cellphone or laptop batteries. You’re annoyed that your cellphone battery is just about worthless 20 months into a two-year contract, but a replacement is only $50, maybe $15 if you buy a knockoff of dubious quality. An EV or PHEV battery costs $5,000-$10,000 to build and that you don’t want to replace. Manufacturing costs are the order of $300-$400 per kilowatt hour for EV batteries. The PHEV Chevrolet Volt battery is 16 kWh, so that’s $4,000-$5,000 today. The base Tesla S uses a 60 kWh battery, or $18,000-$24,000. Tesla chairman Elon Musk has said he sees the cost dropping to $200 per kilowatt hour in the near future, but it’s still a big number.

Here’s the trick: The battery wears out fastest at the extremes of its charge-discharge cycle. If you never discharge the battery below 20-30% and never recharge it past 70%-80%, it retains most of its capacity indefinitely. True, you can never tap into half the energy in the battery, but if you’ve always known your Prius is good for a mile on its own or a Volt for 35 miles, that’s what you expect, not two miles and 70 miles.

GM says 70% of battery capacity, at least, would be typical for a Volt at the end of its lifespan. Your mileage may vary. Some Nissan Leaf owners were annoyed that their EV driving range had fallen dramatically a year or two, from a Nissan-specs range of about 85 miles per charge down to about 60 miles, especially with Leafs in hot weather cities driven up to 20,000 miles a year. Regardless, that’s the majority of the battery capacity still available.

Community energy storage

In addition to powering a small group of homes for a couple days, GM sees these power modules as community storage systems that would cache energy generated at night using cheaper, lower-emissions energy sources (hydro, natural gas, nuclear) and spool it out at high-demand periods: evenings in winter, late afternoons in summer.

The one drawback to the GM-ABB project is that they’re good for a day or two but not the week or two, sometimes longer, of power/grid failure that natural disaster brings on. Most metro New York residents hit by Hurricane Sandy in 2012 were without power for a week to 10 days. For that, you need a generator, ranging from $500 for a portable unit, to $2,500-$5,000 for a standby generator that keeps the essentials going, to a whole house generator at $10,000-$15,000.

One advantage of a battery-powered generator is that it can kick in instantly, just as your $100 UPS does, and you don’t lose what’s unsaved on your PC.

Nissan Leaf: Power your house with the battery still in the car

GM and ABB aren’t the only automakers thinking about using EV batteries to power things other than cars. In Japan, Nissan has shown a power control system that uses the battery still in your existing Leaf to power a typical Japanese house for a day or two. The system is a floorstanding box that connects the car, your house, and the electric grid. It could also deliver power back to the grid at peak periods, then be recharged at night when rates are lowest. “A day or two” of power for a house from a Nissan Leaf should be understood in the global context: The average Japanese home typically draws 10-12 kWh in a day, while the average American home draws 29 kWh.

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