Analysis: why electric vehicle batteries lose power, the second-hand car market and tips to increase your car battery's life and range
Our world has been transformed by lithium-ion (Li-ion) batteries. The technology powers all our phones and laptops, and is taking over how we move, from scooters and wheelchairs to bikes and increasingly electric cars. A colleague once described the li-ion battery as being "like a burning fuse: from the moment you make it, the battery is slowly dying". Let's discuss why this is so, and how you can slow the degradation and extend battery life.
Lithium is an amazing element. It's the third element in the periodic table and is a very light, energetic metal, making it a far better element to use for batteries than lead, the metal of choice for well over a century. The Li-ion battery is the lightest and most durable battery which humanity has discovered in the 240 years since Italian scientists Luigi Galvani and Alessandro Volta first discovered and invented the battery. An invention of the 1980s, it has largely vanquished the older lead and nickel batteries.
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From RTÉ Radio 1's Today with Claire Byrne, motoring journalist Bob Flavin on what to know before buying an electric car
Why does the battery age and die?
All the work of charging and discharging a Li-ion battery is done by the lithium (in the form of an ion) moving back and forth between the positive and negative electrodes. A host of conditions can cause the lithium to be permanently trapped within or on the electrodes unable to work, causing the battery to die.
Old age (in calendar years) and high usage (in kilometres) are two obvious factors for the loss of working lithium. Fast charging, fast discharging, and charging the battery too high are additional factors.
Overheating the battery definitely doesn’t help, while frozen batteries are also a challenge. For this reason, electric car batteries today come with dedicated heating/cooling systems.
What can I do to avoid battery fires?
Electric car fires are rare and EVs are proving themselves to be less fire-prone than conventional cars. Lithium as an element is very reactive and combustible. The early challenge was to get to a stable battery and avoid fires. The technology companies have been very successful at developing safe batteries, partially by having no elemental lithium in the battery. Follow the instructions in the manual and take care of the EV and the charging equipment. Have the EV or charging equipment checked out if there’s any damage or an accident.
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From The Engineers Post, a guide to the types of electric car batteries
What’s with cobalt?
Cobalt has been an essential component in the cathode of Li-ion batteries for decades as it reduces the likelihood of fire and extends the life of the battery. Cobalt has its sustainability challenges partially due to mining practices in the Congo. While many EV batteries still depend on cobalt, they are using a lot more nickel and much less cobalt, typically with eight times more nickel than cobalt.
What about lithium-iron-phosphate (LFP) batteries?
The F in LFP stands for Fe, the Latin based symbol for iron so LFP batteries use iron instead of cobalt. They are cheaper and more stable than the cobalt batteries, but are also bulkier and heavier. Today you can buy models from Tesla and other companies with LFP batteries and no cobalt.
What are the battery warranties?
Battery warranties are provided by the manufacturers, and vary from one to another. The general warranty is tending towards eight years or 160,000 km, whichever comes first, with a minimum retention of 70% of the original capacity. Battery replacement outside of warranty can be prohibitively expensive. On the positive side, these warranties also apply in far hotter countries than Ireland. The Irish climate is mild and temperate, which helps battery life.
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From RTÉ Radio 1's Drivetime, motoring journalist Geraldine Herbert on the second-hand car market
What about second-hand electric cars?
The second-hand market is slowly developing, but there are a very limited number of cars currently on the market. There’s also the problem that it’s difficult to tell the health of the battery and the available life and range. A United Nations standard, UN GTR22, is being developed to address this problem, but is still in the works.
Should I just wait for the next battery technology?
You’ll be waiting! We have had three successful rechargeable battery technologies in the last 200 years based on lead, nickel and lithium. Solid-state lithium-ion batteries are mentioned but are many years away from being viable for electric cars. The present industry goals are simply to make the existing technology more sustainable, long-lasting and recyclable while keeping costs down.
A good reason for waiting is to let the technologies keep maturing and car prices dropping, as has been happening for the past decade. It’s also reasonable at this time to have the view that an electric car does not suit your driving needs, budget or environmental expectations.
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From Auto Trader, does driving fast kill electric car batteries?
How can I extend the life of my electric car battery?
Regularly charge the battery, and stay within the range of 20 to 80%
It's better for battery life to have regular shallow charges in response to regular shallow discharges. For example, charging every day or two, as you drive, is better than having a week of driving and waiting until the end of the week for a deeper charge.
If we don't fully charge the cobalt-based battery, we can get the battery to achieve a longer life. Manufacturers Kia, VW, Tesla and others recommend charging to only 80% of the battery’s full useable capacity. Occasionally charge to 100 % if you really need the range, but don’t make a habit of it. This is not the case for LFP and Tesla actually recommend regular charging of LFP to 100%.
Discharging your battery to zero does not necessarily hurt the life of the battery, but it is important for battery life to then start charging as soon as possible. A level of 20 % is strongly advised by VW and Mercedes as a nominal minimum battery charge in order to have an adequate reserve to avoid deep battery discharges.
Avoid frequent fast accelerations, high-speed driving and high-power charging
High power charging is great for rapid refuelling, but the battery will heat up due to the high power. Regular high-power charging will definitely shorten the life of the battery. The same is true of high-power discharges of the battery. Fast accelerations and high speeds will not only drain the battery faster, but will also shorten the life.
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From CNET, how to reuse, repurpose, recycle and reduce old EV batteries
Don’t forget to have the vehicle charged when you are away
Mercedes Benz suggest a charge of between 30% and 50% if your car sitting unused for an extended period, and to not let the charge drop below 20%. During hot weather, it is also recommended to park in the shade to avoid high temperatures. The battery naturally discharges when not in use so follow the instructions in your manual to keep the battery healthy. Again, it is strongly recommended not to fully charge the battery.
Remember the published range is deceptive
The standard Worldwide Harmonized Light Vehicle Test Procedure (WLTP) values are published in Ireland for range. The WLTP range in kilometres (km) is difficult to achieve in typical driving as the standardized test does not consider much of real-life driving: passengers, hills, driving style, cargo, air conditioning, etc.
For a more realistic range, subtract 20% from WLTP to start and subtract another 10 to 20% in winter. Thus, if the published WLTP range is 500km, the real driving range might be closer to 400km in summer and about 340km in winter. Use the 80% battery charge limit tip mentioned above and the ranges reduce to 320km in summer and 260km in winter. The real range drops further as the battery degrades.
Consider a bigger battery if doing a lot of mileage
The car and battery should last the warranty period and beyond if you're a typical driver doing about 50km a day, or about 18,000km a year. However, much higher annual mileage and a small battery means that the battery will degrade faster. It's better to have a bigger battery, with all the cost and weight penalties, in order for the battery to survive. Results published by Tesla indicate that their batteries are still retaining 90% of capacity after over 160,000k, which is impressive.
The Chinese language edition of the author’s Electric Powertrain: Energy Systems, Power Electronics and Drives for Hybrid, Electric and Fuel Cell Vehicles 电驱动系统——混动、纯电动与燃料电池汽车的能量系统、功率电子和传动 was published by China Machine Press (Beijing) in 2021
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
