How Long do Electric Car Batteries Really Last?

Gauging the risks, and rewards, of driving an electric-powered car with the father of the Chevy Volt’s battery system.

bySteven Lang| PUBLISHED Aug 11, 2016 4:55 PM
How Long do Electric Car Batteries Really Last?

231,853 miles. That was the odometer readout on my wife’s recently sold 2002 Toyota Prius.

I sold it cheap—as in, $800 cheap—because the electric battery is on life support. The dashboard recently issued what can only be called, “The Orange Exclamation Point Of Death,” which on these Toyotas comes in the form of a big, bright triangle and a non-stop 120-decibel screeching noise that will haunt your very soul.

“BEEEEEEEPPPP!” That's the car saying, basically, “Don’t even drive me 50 feet! Get out! Have me towed!” Since I didn’t want this car to become a 3,000-pound paperweight, or pay for a $1,500 remanufactured battery, I decided to sell it for $800 to a hybrid enthusiast who wants to Frankenstein two of these first-gen Prius' into one. God bless him!

Hybrids in general have taken a marketplace journey not too different from this very Prius. From the weird hobbyist, to the mainstream car buyer, back to hobbyists who are more interested in technology than tightwaddery.

Hybrids have been money-losers for nearly all automakers, and with gas prices creeping below two bucks a gallon, it’s looking like the lull in demand will last for a while. In fact, 80 percent of hybrid models that were in the market over the last 15 years are now defunct, and the sales of the brand-new 2016 Toyota Prius are down over 10 percent from last year. Even Honda, an automaker well known for making super-efficient motors for everything from scooters to jet planes, has struggled to field a successful hybrid.

It’s a tough market for gas-sippers, and hybrids are far from alone these days. Through no fault of their own they've recently lost the media popularity contest to electric vehicles, which have become the "new" new answer to the future of motorized transportation. That is, until you take a deeper dive and look squarely at the fact that no pure electric vehicle has ever made a dime in profit, ever.

Electric cars, while popular and benefitting from generous subsidies, collectively make up less than 1 percent of today’s new car market. Range anxiety, development costs, and low gas prices are all limiting the demand for anything that has a battery these days. But there’s one question in particular that has kept a large number of car shoppers, even the adventurous ones, on the sidelines when it comes to hybrids and electric vehicles: the question of just how long those batteries last.

To answer this question I contacted Bill Wallace, Director of Global Battery Systems Engineering at General Motors. Both generations of the Chevrolet Volt have been his babies, and he has invested a career into making their batteries endure for the long haul.

I started by popping him the big question.

The Drive: In terms of years and cycles (charging and depleting the battery), how long is the Volt’s battery designed to last, on average?

Bill Wallace: "In extreme hot climates such as Phoenix, the Chevy Volt will last at least 10 years, 150,000 miles, and 6,000 cycles. This requirement has held quite steadily for both generations of the Chevy Volt. We use OnStar to track the performance of our vehicles and this benchmark of durability has remained consistent for all General Motors vehicles that will use the Volt powertrain."

What are the forecasted financial savings of the Volt versus the average non-EV vehicle?

"The EPA estimates the Volt's fuel economy at 106 mpg in electric mode, and 42 mpg combined for the gas engine. Over 10 years and 150,000 miles, you should save about $11,000 versus the average vehicle with an internal combustion engine that now gets about 25 miles per gallon.

"Keep in mind this savings depends on how you drive and when you recharge the car. Electric companies often offer cheaper rates in the late evening to early morning. You can easily time an electric battery’s charging period to take advantage of that savings."

Does a Volt use a nickel-metal or lithium-ion battery? I’m not sure most people know the difference and/or care right now, but it seems like there is a bit of a change taking place in the auto industry when it comes to EV batteries.

"We use a lithium-ion battery. Primarily because of energy density and weight. A lithium-ion battery can store almost twice the energy of a nickel-metal battery and is less than half the weight. This allows us to offer a smaller battery with the same amount of energy needed to power our hybrid and electric vehicles. Also, when it comes to a deep discharge, lithium ion batteries have proven to be far more durable."

In the earlier days of hybrid vehicles in the U.S., from 2001-2005, there were issues with the longevity of hybrids. What has changed?

"There have been several lessons learned since that timeframe. First is software. Estimating the state of charge on a battery has improved vastly. One of the reasons why batteries were wearing out prematurely was because the individual cells were being overcharged and undercharged. This has a serious impact on battery life.

"Also, the systems that managed charging and discharging were uneven. Some cells within the battery would become hot. This was a big problem because batteries are only as strong as the weakest cell. Over time, you developed hot spots on the battery, which resulted in premature battery failure.

"Finally, it took time to resolve the unique chemistry used for nickel-metal batteries. Today, lithium-ion now offers better inherent cycle lives, which make them more durable."

In terms of temperature variations, are there variances in the lifespan of hybrid batteries in extreme climates? Let's compare a hot climate like Phoenix, Arizona with the cold of Anchorage, Alaska.

"All batteries have their life shortened by heat. So in the absence of a quality thermal conditioning and cooling system, all batteries will lose more life in Arizona versus Alaska.

"Without an effective cooling system, a 23-degree (Fahrenheit) change can cut a battery's life in half, so it's an incredibly important issue, which is why cooling systems are essential for the long-term owner of a hybrid or electric vehicle."

TD: The image and performance of electric cars has changed quite a bit over the last five years. In your opinion, why have certain hybrids become so fast? Because not too long ago they were well known for being underpowered and almost asthmatic?

"Thanks to a stronger battery and a more robust battery pack, a lot of manufacturers have finally been able to avoid the rubber band of raspiness that came with older hybrids.

"Performance has become a priority for customers, too, and we're glad these changes have taken place because it will help help hybrids and electric cars become more popular. Fuel economy is starting to take a back seat to fun when it comes to making these vehicles popular, and we want our battery technology to be the best it can possibly be in today’s marketplace."

Hybrids like my once-prized Prius built a following—right up to the point when gas prices went into a free fall. If that early generation hybrid battery of mine had lasted beyond 231,000 miles, I would probably still be driving it today. So might other Prius owners who have returned to driving cars with conventional powertrains. The consumer's desire to buy and keep a hybrid is usually based on benefits outweighing the financial risk at purchase time; but, as Wallace points out, buying decisions aren't entirely economic.

Regardless of the improvements automakers have made in hybrid powertrain systems since 2002, the image a car conveys influences many purchases. Hybrids and electric vehicles are in the midst of trying to change their image, from a car that attracts technophiles, tree huggers, and tightwads, to a vehicle that can offer a higher level of performance, reliability, and fun. In the 14 years and 231,853 miles it took my Prius battery to finally start to die, perception of the hybrid car has changed radically. Expect history to repeat itself when you try to calculate the number of miles you're able to put on your new Volt or Prius—your results may vary, but the batteries might last longer than the whole idea of your car. For next generation of hybrids and electric vehicles to succeed, they’ll have to show that they’re not only the best cars to own based on the bottom line, but also based on that magic elixir known as performance.