Battery Technology – Page 2 – The Plugin Report

Every year an electric car loses range. Data from real-world electric vehicle driving shows batteries are faring better than experts thought in regard to maintaining battery range. Electric cars lose 2.3% of range per year on average. Over time, a 150-mile range electric car will lose 17-miles of range in five years. At this rate, batteries will outlast the usable life of the vehicle. The loss of range depends on the make, model, and year of the electric vehicle. As more electric vehicles hit the road, are driven under varying conditions, and data is collected all sources point to range loss over time is not something one should worry about when purchasing an electric car. But let’s look at the data to see what range can expect if you purchase an electric car - new or used. Range Over Time of an Electric Car The best data on electric car battery range over time comes from a fleet-telematics company, Geotab. Fleet-telematics are systems that collect data on vehicle location, driver behavior, engine diagnostics, and vehicle activity. They then do cool stuff with it, like help us feel better about an electric car’s long term battery life and performance. Geotab collected real-world data from 6,300 electric cars, representing 1.8 million days of data. The study was on 21 distinct vehicle models, representing 64 makes, models, and years. What did they find about the electric cars losing range over time? If you purchase an older electric car, the battery has deteriorated. But the decline in the range is minor and won’t impact your day-to-day commute needs. On average, one can expect a lithium-ion battery to lose 2.3% of its ability to hold a charge each year. Consider 2.3% your benchmark but the battery degradation does depend on the make, model, and year of the vehicle. If you are considering purchasing an electric car and are concerned with loss of range over time then take a look at Geotab’s EV Battery Degradation Tool. The tool is an excellent way to compare the battery performance of different electric vehicles. You are right to explore this issue as the capacity loss will impact range, cost of ownership, and resale value. For example, using the Battery Degradation Tool one can see a 2017 Nissan Leaf battery is expected to be 94.7% of the original capacity or the battery’s state of health (SOH). While a 2017 BMW i3 is 84.2% SOH. That is a considerable difference if you are planning on driving a lot. Electric cars are so new that there is little hard data, mostly anecdotal about long term battery health. But the evidence is mounting that long term performance of batteries should not be a concern for buyers and owners. Tesloop, a Tesla rental service company in California has driven its seven Model 3s, Xs, and Ss over 300,000 miles each, 1,700 miles per month. They have no plans to remove them from service. A Model X with 330,000 miles experienced a range drop of 23%, from 260 miles to 200 miles. 419 Tesla owners worked together to pool their car’s battery degradation over time. The results were Tesla’s batteries retained 95.6% SOH (percent of original capacity) after 31,068 miles (50,000 km). The rate of decline was not linear but slowed over time. It reached 94% SOH at 62,137 miles (100,000 km). Source: Atlas MaxRange Tesla Battery Survey (qz.com) A 2017 Teslanomics survey of Tesla owners found battery degradation stabilized at around 91% SOH. Why Electric Car Batteries Lose Range Over Time As the Tesla data shows, a battery’s state of health is not a linear decrease. The Geotab data is linear as a simplification across the large sample size. As a general rule, batteries are expected to decline non-linearly. An initial drop is followed by a continued decline at a moderate pace, leading to a sharp drop-off at the end of life. EVs on the road are not old enough to have experienced this sharp drop-off. In fact, Tesla says it is working on battery technology that would enable an electric car battery to be driven one million miles before the drop-off. Consumer Reports estimates the average electric car’s battery-pack lifespan to be 200,000 miles before the range is restricted. 200,000-mile lifespan is 17-years if driven 12,000 miles per year. State of health (SOH) measures a battery’s ability to store energy over time. A battery starts at 100% SOH and degrades permanently over time. A 100 kWh battery starts at 100% SOH but after two years has 95% SOH would act like a 95 kWh battery. SOH is not the same as battery range but SOH does reduce the distance a car can travel on those kWh. An EV’s range is also impacted by climate, topography, cargo load, and driving habits. Lithium-ion battery health is impacted by the following factors in order of largest to least impact: TimeHigh temperaturesOperating at high and low state of chargeHigh electric currentUsage (energy cycles) Temperature Impact on Range Loss Lithium-ion batteries do not fare well in extreme heat. EVs operating in hot climates can expect a larger decrease in range over time. But, many electric cars are equipped with cooling systems for the battery-pack. Here is where you can see a difference in car brand performance on long-term range degradation. Tesla’s liquid-cooled batteries have a higher range over time compared to Nissan Leaf’s passive-air cooled system (Geotab data). Managing the batteries temperature is a differentiator for carmakers going forward to reduce range loss with time. Operating Range Draining most or all of a battery’s charge can cut into the long term capacity. Operating at near-zero charge on a regular basis has shown to decrease the state of health of the battery. This was a bigger problem for older cars that had a smaller range. Now with Nissan Leafs having a 150-mile range and Tesla’s with over 300-mile ranges, users only use a fraction of the battery’s capacity before they charge for the night. High Electric Current Those Level 3 DC Fast Charging stations are great. They can bring an EV’s batteries up to 80% capacity in 30-minutes. But they can take a toll on the health of the battery. The high electric current makes the battery-pack hot, leading to battery degradation as hot temperature does in the example above. The impact of excessively using Level 3 DC Fast Charging stations is limited. A study done on two identical 2012 Nissan Leafs by Idaho National Laboratory found using Level 3 chargers isn’t a pronounced issue. For 50,000 miles they charged one leaf exclusively on a Level 2 240-volt home charger and the other Leaf on public Level 3 chargers. The Level 3 charged car had a 4% decrease in capacity compared to the Level 2 charged car. Research has shown all these play a part in battery health but long-term, real-world performance date has only started to be collected. As EVs on the road reach a decade old, more data on range loss over time will paint a clearer picture of battery performance and improvements needed to maintain the battery’s health and range. How to Reduce Range Loss Over Time The data and recommendations from Geotab recommend maintaining an electric car’s battery state of health by the following guidance. reducing exposure to extreme temperatures and heatkeeping EVs charged between 20% and 80%minimize DC fast charging Items two and three are under the control of the owner while it is harder to control the climate. Following this guidance will improve the long-term range and health of the battery but perhaps only a few percentage points. The EVs studied all show a decline in performance with age but it is strongly noted these batteries will outlive the car’s components. While apprehension on battery life and range is a major factor for people purchasing EVs, their performance has been outstanding and continues to improve as battery technology improves. Geotab’s data, informal Tesla super-fan data, and government research are helping to overcome electric vehicle misconceptions. Misconceptions like electric cars lose a substantial amount of range over time. Cox Automotive survey of people considering to purchase an EV, “50% viewed the average battery life at 100,000 miles or more, and 46% thought average battery life was 65,000 miles or less.” Real-world data is finding the opposite to be true. Electric cars lose range over time but at a rate that is unlikely to impact an owner’s day-to-day needs. Carmakers expect the batteries to outlast the vehicle’s lifespan. When shopping for a used electric car, it is wise to note the actual range of the battery. If you are purchasing a 2012 Nissan Leaf then a 10% decrease in battery capacity is significant on a battery that only had a 70-mile range to start with.