Battery Durability and Longevity

By · March 13, 2010

Canadian Cold-Weather Testing

GM tests the Volt in Kapuskasing, Ontario Canada.

First of all, the lithium ion batteries in plug-in vehicles should not be confused with the earlier battery technology developed for laptops and consumer electronics devices. You know, those laptops that infamously caught on fire in the YouTube video. The "thermal runaway" issue was solved by replacing some of the battery materials (cobalt oxides, if you must know) with safer chemistries.

The generic term "lithium ion battery" is applied to a variety of battery designs (lithium oxide manganese spinel, lithium titanate, lithium iron phosphate) that the majority of us who struggled through high school chemistry don't need or want to understand. The shape of the batteries—which are actually packs of cells wired together—has also gotten a makeover. The cylinders used in electronics have given way to easier-to-configure "large format" rectangular (prismatic) batteries.

Careful Management

If lithium ion batteries were to be fully charged and depleted every day—known as deep cycles—they might only last a few years. To greatly extend the batteries' useful life, plug-in vehicles contain sophisticated software that keeps them from fully draining. Battery management systems are the essential brains of the system, enabling the batteries to be partially charged/discharged up to 300,000 times—known as "shallow cycles.”

The Chevrolet Volt battery is put into the vibration shaker to simulate real-world conditions over time. The battery sustains shaking, power cycling and temperature cycling.

Simply put, you can take as many trips as you'd like—minimally discharging and charging the batteries over and over again—and it won't perceptibly reduce their ability to store energy. The battery management system also prevents the battery from overcharging and monitors the flow of electricity down from the grid to similarly protect the batteries. The net result is that the batteries are expected to at least last the lifetime of the vehicle.

Oversized for Extra Measure

It’s true that lithium ion cells lose some of their ability to store energy over time, and are expected to have a useful life of five to seven years. But automakers compensate for this by oversizing the battery cells and the battery pack so that a loss in storage capacity shouldn't be noticeable for eight years or more. Once the battery begins to lose capacity, you can choose to either continuing driving your plug-in vehicle with diminished range, or trade in the batteries for a fresh set—although pricing for that is completely undetermined.

The battery shelf life—for anyone crazy enough to buy a plug-in vehicle and to let it sit in the garage—is around 20 years. The batteries don't require any maintenance, and fiddling with them is highly discouraged as they produce a considerable jolt of more than 3 volts.

Hot and Bothered

Chevy Volt engineers put the vehicle through its paces in frigid conditions.

The Achilles' heel for lithium ion batteries is temperature. If the battery temperature exceeds 104 degrees Fahrenheit, they can suffer a permanent loss of up to 20 percent of storage capacity. Over time a plug-in owner in the moderate Northwest could see a longer useful life of his or her batteries than someone in Arizona who frequently parks the car outside. Frigid temperatures can also take a short term toll on performance, but won't impact capacity in the long run. For example, if the battery temperature drops below freezing, the chemical reaction that produces the power slows, providing less juice to march up a hill, but as the battery warms, the performance returns.

Comments

· · 4 years ago

John,
I enjoyed your post on battery durability and longevity; very informative. I am planning on getting a Nissan Leaf and have a question. Do I have to “train” the battery? In laptop computers I have used in the past, unless you unplugged the computer and let the battery lean that it was OK to almost run out of power, the battery would not allow the computer to run down and a warning message would be displayed advising me to plug in the computer before it shut itself down. Is that the same with the battery in the Leaf or can I plug it in every night and not worry? My daily commute is 44 miles round trip and I potentially could do 2 days without plugging the car in.
Thanks,
John P

· · 4 years ago

I am also planning on purchasing a LEAF and have been doing a lot of EV-related reading lately. My understanding is that you should be able to plug in the LEAF every night and not worry. Actually, this would be preferable, as having shallower discharge cycles should help to prolong the life of the battery. Also, it probably wouldn't be wise to plan on driving 88 miles between charges, as range can be highly variable depending on driving conditions, and you need to have some margin of error.

· · 4 years ago

My understanding is that plugging in a Leaf whenever you have the chance will not be a problem at all. Just like the article states these batteries have sophisticated software controlling the charging. Our laptops have no such luck. While the chemistry and function of the battery pack in the Prius is very different I can state that my performance after six years has not changed yet.

· · 4 years ago

I have a ?, The Nissan Leaf has a solar Panel on rear spoiler area,I have read that this will trickle Charge the 12 volt Battery only ?

· · 4 years ago

@TechExplorer,
A tiny solar panel on the rear spoiler can't produce more than 2 or 3 watts max. At this rate, it would take more than 1300 days or 4 years to charge a 20 kWhr battery such as the Leaf's primary battery - not really worth the effort.
Covering the whole car with solar panels might produce 150 watts max so it could charge in a little over 26 days. Still hardly worthwhile.
What a solar panel really can do:
On hot days, when parked in the sun, a solar panel on the spoiler or roof can power a circulating fan. This will keep the inside temperature close to ambient temperature and thus permit a less-powerful, more efficient air conditioner. Car air conditioners are very powerful in order to bring the interior temperature down from well over 100 degrees to comfortable ranges quickly for passenger comfort. I suspect this is what the Leaf will do. It will also keep clocks and housekeeping computers from draining the aux battery when parked for a long time. If you want solar to power your car, put a multi-kWhr solar array on your house or carport. I have a 5.5 kWhr array on my house that offsets my daily 80 mile commute in an EV.
This is all good and probably worthwhile.

· · 4 years ago

Thanks,I saw a video some where on you tube with that same basic info,getting off the subject ,what have anyone seen about using the infrared spectrum for solar cells,this way it charges even @ night,cloudy days,etc ?

· · 4 years ago

Hey TechExplorer,
Your brain is really going in full gear! I'm no solar cell or PhotoVoltaic (PV) expert by any means, however, I do know that a lot of the efforts in PV development for extremely high efficiency PV as used by satellites focuses on finding materials that capture as many spectra of the light as possible - just what you seem to be thinking about.
These so-called multi-junction cells have different layers made of different semiconductor materials, in rows III and V on the periodic table (eg Ga-AS, Ga-In-P, etc). Each layer captures different wavelengths of sunlight. Of course, as one stacks up layers, the lower layers get less sunlight since the higher layers filter out a lot of the desired wavelengths. I believe that the state of the art with multi-junction PV is around 4 layers and efficiencies of around 30% are being attained but they are extremely expensive to produce.
Commercial PV pretty much exclusively uses only a single Silicon junction because it is the cheapest and gets the most light from the sun of any other III or V column semiconductor. The best Si cells get around 20% efficiency today.
I don't know how much IR energy gets through on cloudy days but, since it is cold on rainy days, I suspect it isn't very much. I'm pretty sure that there isn't much at night. I doubt that it would be enough to be worth collecting - but I'd be happy to be wrong here!
Even 100% of the sun's energy only provides about 1 kW per square meter and the IR would be even less so it would take a lot longer than the 26 days to charge with visible light that I mentioned above, maybe a year?
Solar energy is great but it takes collection area to harvest it, no matter what part you take.

· · 4 years ago

Have not read anywhere,but has anyone combined the latest EV tech. with Flywheel tech. to possibly produce a Car. would take far less energy to keep flywheel @ speed and allow Flywheel to drive vehicle from a stop,etc.

· · 4 years ago

Flywheel could stay in motion for weeks

· ChuckR (not verified) · 4 years ago

104 deg F sounds like an awfully low temperature to cause a permanent loss of up to 20 percent of storage capacity. Maybe 104 deg C ?

· Freddy (not verified) · 4 years ago

We will have a more peaceful world if electric cars are the majority.
No noise and less wars.

· Anonymous (not verified) · 4 years ago

Can someone please comment on the 104 deg. and permanent storage capacity loss issue? It can get 105-109 in the summer. So, one hot day and the battery is permanently damaged?

· Nobody (not verified) · 3 years ago

I think from the context the 20% loss in capacity is for that day or that particular charge, e.g. you wake up and drive to the store and use 5% of the battery; while parked the battery reaches over 104 degrees; you get back in your car and the battery has gone from 95% to 75% loosing 20% due to the high temperatures. This will result in having to charge the battery more frequently and that is what shortens the overall life span of the battery. Unlike the battery which is cold and performs as though it has less power although the power returns once the battery is warm.

· · 2 years ago

I agree that batteries used for laptops should not be used for electric cars. Those batteries overheat so quickly and we wouldn't want to take the risk of having cars overheat that fast. I have surveyed some mechanics and they are against it too. They have said that repairing battery from laptops is different from repairing a car.

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