What You Should Know About Today’s Electric Car Batteries

 In EV Charging, EV Industry

Most consumers regard batteries with a slight hint of contempt and mistrust. Who can blame them? Based on their experience with cellphones and laptops, batteries are needy snowflakes with fickle charging schedules, and get sucked dry at the least convenient moment.

But unlike their temperamental counterparts, electric vehicle batteries are different. They’re designed to be more robust, as they carry a heavier load and last much longer. Of course, they’re also a little more expensive than your average iPhone battery.

Still, costs for EV batteries have been falling faster than most could have expected. In fact, EV battery costs declined by 35 percent between 2014 and 2015.

That’s the result of changes to cell chemistry, manufacturing processes and aggressive pricing by large manufacturers elbowing their way into the lucrative market. Things are getting competitive, and OPEC is feeling the heat.

They’re predicting there will be 1.7 million EVs on the road by 2020, while Bloomberg New Energy Finance estimates it will be more like 7.4 million, with 2 million sold in 2020 alone. Bloomberg also expects electric cars to make up 35 percent of light vehicle sales by 2040. Recent developments, such as rapidly decreasing EV battery costs, may give a slight edge to Bloomberg’s crystal ball.

Experts say EV battery costs could be under $100/kilowatt hour by 2020, and after that, go down to about $80/kilowatt hour.”

– John McElroy, Ward’s Auto

Reducing Battery Costs

It’s no secret that batteries represent a large chunk of EV change, and are presumed to be one of the bigger stumbling blocks to EV ownership. Reducing this cost quickly & neatly trims EV cost. The battery cells used in the Chevy Bolt are now running at $145/kWh – should that drop to $100/kWh, the battery pack would cost $4,000, significantly slashing the cost of a Bolt.

Of course, cell prices and battery pack prices are two different entities. A battery pack includes individual cells, supporting structure, a cell cooling system and a battery management system. The price of a Tesla battery pack? A cool $190/kWh. But as production ramps up in Tesla‘s Nevada gigafactory, that may change.

The Tesla gigafactory in Nevada.

The Tesla gigafactory in Nevada.

Should battery prices fall below $100/kWh, EV sales could skyrocket to one million vehicles a year, along with another million plug-in hybrids. And market share of vehicles with electric motors could well surge from the current 1 percent to over 10 percent in just a few short years.

What about battery degradation?

But there’s more to the EV battery consideration than cost. Just how much bang do you get for your EV buck? PlugIn America surveyed Tesla Model S owners, covering 519 vehicles that travelled 13,992,158 total miles – or an average of 17,523 miles per year (that’s actually more than the 13,476 average annual mileage calculated by the Federal Highway Administration).

It turns out that the Model S lost about 5 percent of its power in the first 50,000 miles, at which point, battery degradation slowed. Some with 100,000 plus miles had battery degradation of less than 8 percent. Elon Musk claims to have a Tesla battery pack with over 500,000 simulated miles still running at over 80 percent of its original capacity!

Model S Reported Battery Capacity vs Miles Driven

Reported battery capacity (by the vehicle) versus miles driven. Graph from PlugIn America survey linked above.

What factors affect EV battery life?

To understand what impacts a battery’s life, it’s important to first understand how it works. EV batteries are lithium based – when they are charged and discharged once, it’s called a cycle. A battery’s capacity will degrade as the cycle number increases. And battery life is measured in those cycles, with the industry standard of cycles close to 80 percent considered a benchmark.

So what shortens the life of a lithium battery? A number of factors:

  1. High temperatures
  2. Overcharging or high voltage
  3. Deep discharges or low voltage
  4. High discharges or charge current

When a lithium battery is charged, the voltage slowly rises. When it reaches full charge, voltage is at its highest and will not go up any more. There’s a need to keep voltage from getting excessive, which is why batteries come with a battery management system (BMS). These control the charging voltage so maximum charging voltage and temperature is never exceeded.

Automakers Backing Up EV Batteries with Warranty

At the end of the day, the question still stands – how reliable are EV batteries? Like many other commodities, the true test is the willingness of the manufacturer to back up their product in writing – the warranty.

While EV manufacturers do provide warranties against excessive capacity loss, some warranties are better than others. BMW, Chevrolet, Kia, Mercedes-Benz, Smart and Volkswagen will warranty their batteries to various levels. On the other hand, Fiat, Ford, Mitsubishi and Tesla specifically exclude capacity from their EV warranty, providing only for the actual failure of the battery – not any loss of capacity.

It’s interesting to note that Nissan initially figured the LEAF would retain 80 percent capacity after five years, and 70 percent after 10 years. Some LEAF owners exceeded this estimate, while others fell short. Now, Nissan offers a capacity warranty – should a LEAF lose four bars on its capacity gauge (this equates to about 70 percent capacity, but is not stipulated as such in the warranty) before 60 months or 60,000 miles, whichever comes first, Nissan will repair or replace the battery for free. For the 2016 LEAF, which came equipped with a 30 kWh battery, Nissan extended the warranty to 96 months or 100,000 miles!

Here are some other examples of how manufacturers cover EV batteries:

  1. BMW i3 is covered for eight years or 100,000 miles, to 70 percent capacity
  2. Chevrolet Bolt EV is covered for eight years or 100,000 miles, to 60 percent capacity
  3. Kia Soul EV is covered for 10 years or 100,000 miles, to 70 percent capacity
  4. Mercedes B250e is covered for eight years or 100,000 miles to 70 percent capacity
  5. Volkswagen e-Golf is covered for eight years or 100,000 miles to 70 percent capacity.

When automakers back up their product with solid warranties, it bolsters consumer confidence – and sales.

Battery packs in Nissan Leaf

Nissan LEAF pictured. In most modern electric vehicles, heavy battery packs sit below the passengers—making them easier to steer.

Tips for Maintaining Your EV Battery

Another indicator of growing consumer confidence is also apparent in the proliferation of online do-it-yourself EV battery care tips. Some examples include:

  • Don’t leave battery sitting at 100 percent state of charge too often, because it’s stressful for the battery
  • Avoid deep discharging of battery
  • Avoid extreme temperatures (store in a garage whenever possible)
  • What to do with EV if going away on vacation? Set charge level to 50 percent and leave it plugged in – if you can.
  • Minimize fast charging whenever possible

Whenever do-it-yourself tips start making an appearance, it signals the emergence of a more engaged consumer. And as EV batteries become more affordable, durable, and backed up by manufacturer warranties, the last barriers to EV ownership are bound to start tumbling down.

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  • Sam

    Not sure I will get an answer, but what will the replacement battery pack cost me if I needed one today? What happens to my old battery? How is it disposed of?


      It will cost from $5,500-$8,000 and your old battery will be recycled.

      • Satyagraha

        Over 90 % recyclable which is really good!

    • BHShaman

      Cost are always falling. Replacement cost are determined by Brand, as it includes dismantling the housing, replacing the battery, and reinstalling the housing. Just trade it in. They last 100,000 so get your trade in value before the risk hits.

      I suspect that eventually used EVs will already have the replacement done and factored into the used car price, like Timing Belts are now for vehicles over 60k miles.

    • Satyagraha

      Don’t worry about it. You can’t go wrong by going all electric, and solar! Change the world! It’s your choice! “Solar beats everything hands down, including natural gas!” -Elon Musk

  • Jason Bacon

    One error here…
    Leaf owners should *NOT* leave the car plugged in while away for extended periods, at least for early models (I have a 2013). If you do, the accessory battery will go dead and you will need to jump start the car. Oddly, the accessory battery only gets charged while the car is unplugged and turned on. I think this is a design flaw in an otherwise fabulous car…

  • Donald Wheeler

    I’m new at this…my wife and I are looking at the Chev Bolt and charging it with Solar. Charging systems ,I’ve been told have safeties built in to not over charge batteries? Lots of things are told when buying. My question is can the car be plugged in for extended periods. Say over night in many cases 2)-3) days?
    Another quick one .. what can be expected for mileage? Considering normal driving mostly flat ground , but air conditioning and entertainment running.