The use of lithium batteries in electric vehicles is driving industry research to study how to increase it duration (Tesla at the forefront), and at the same time experts have begun to analyze the causes of failures and natural deterioration. Let's try to understand how long does a lithium battery in an electric car last and how does the warranty work.
How long does an electric car battery last?
How long does a lithium battery in an electric car last?? While the duration of 3 years and 500 charging cycles for a PC battery or a smartphone is acceptable, the 8 years of life for an electric car battery, which may seem like a lot, actually they worry the buyer of a EV.
La Replacing the battery pack in an electric car costs a lot and costs as much as a compact car with traditional endothermic engine. If battery life could be extended, for example, up to 20 years, the high initial investment required to purchase an electric car could be better justified.
Electric vehicle manufacturers choose batteries that are optimized for the duration rather than for a high specific energy; indeed these batteries are bigger and heavier than those used in consumer electronics.
Why does the lithium battery degrade?
Why does the Li-ion battery degrade? More in-depth studies have revealed that the lithium ions, responsible for transporting the electric charges between the electrodes, were decreased in the cathode e permanently passed on the anode; then the cathode had a lithium concentration lower compared to a new cell. This phenomenon is irreversible and therefore it is inevitable the battery degradation.
The researchers studied efficiency by which electrons are transferred during charge and discharge cycles, called Coulomb efficiency. While charging the lithium precipitates on the anode in graphite and change the potential difference. You create a movie called Solid Electrolyte Interface (SEI) formed by the lithium atoms on the anode surface.
Nissan Leaf battery life test, how long do they last?
The batteries of the Leaf have been subjected to tough test cycles. Nissan had selected for the first series of the Leaf a lithium manganese battery, due to its attractive performance. The test protocol employed included a fast charge at 1,5 Coulomb (C) in less than an hour and a download a 2,5 C for 20 minutes at one temperature of about 60 °C.
Battery capacity loss over time
Subjected to these harsh conditions, the long-lasting battery should lose its 10% of the capacity after 500 charging cycles, which represent 1-2 years of driving. This test simulated driving the electric vehicle in very heavy conditions (including skid marks typical of aggressive driving) and in spite of everything the battery recharge capacity remained around 90%.
Causes loss of lithium battery capacity
Despite such thorough and intensive testing, owners of the first series Leaf have experienced a 27,5% capacity loss after two years of use and without particularly aggressive driving. What caused this big difference from the tests?
The researchers disassembled the damaged batteries: unrolling the one and a half meter long strip of metal tape that forms the anode and cathode of the battery, covered with oxides, they found that the end nanomaterial structure it had become coarse.
Film that damages lithium-ion batteries
This film, consisting of lithium oxide e lithium carbonate, grows with each charging cycle: the layer becomes thicker and forms a barrier that hinders interaction with the graphite. THE'Coulomb efficiency varies depending on the cell type, as can be seen in the table.
Lithium – Cobalt oxide
Good, drops slightly at 50-60°C
High capacity, limited power, fragile
Smartphone e PC laptop
Lithium – Manganese oxide
Low, drops further at 40°C
High capacity, high power, resistant to heavy use.
Tools, e-bikes, electric vehicles, medical instruments, UPS
Lithium – iron phosphate
Medium, set at 50-60°C
Lithium – Oxides of nickel, manganese and cobalt
Good, a small drop at 60°C
Lithium – Nickel, cobalt and aluminum oxides
not yet measured
Electric vehicles (Tesla Model S), batteries for grid-connected storage systems
Long life but expensive and with low specific energy
At the cathode occurs a similar phenomenon, also known as electrolyte oxidation (EO).
Li-ion battery degradation vs charge level
It was also found that the longer the battery remains under a high voltage, the faster the degradation occurs.
high voltage in this case we mean a cell voltage equal to 4,10 volt. The comparative studies were carried out by loading the cells up to 3,92 Volts.
Why do electric car batteries get damaged when they are 100% charged?
Summarizing the laboratory results obtained from the lithium-manganese batteries cylinder heads of the Nissan Leaf it has been established that one of the main causes of damage caused to the battery is the permanence under tension of high cell and high temperatures.
The Coulomb efficiency test revealed that the latter two conditions cause more damage of charge and discharge cycles.
For this reason it is recommended not to fully charge the batteries of the electric car beyond 80% if not necessary. It is recommended to charge the battery to 100% and thus level the voltage of all the cells just before tackling a longer journey, in order to bring the battery voltage back to lower values.
On this sign, MAVIC has inserted a system (Intelligent Flight Battery) for self-discharge of the drone battery after a few days (the number of days can be set).
Tips to extend the life of the lithium-ion battery
In this regard, we report i top tips from DJi to extend the life of lithium-ion batteries of a drone on which you can get ideas…
- Warm up the cold battery.
- Do not stress the battery in case of high temperatures.
- Store the battery properly. To preserve the battery, choose to store it in a dry environment, with a temperature between 22°C and 28°C. Do not store the battery near heat sources, and away from liquids.
- Do not store the battery with a maximum or too low charge for a long time. If you need to store the battery for longer than 10 days, then before doing so, make sure it has a charge between 40 and 65% of the total. You can use the DJI GO app and set the self-download time (from 1 to 10 days). If the battery is stored with less than 10% charge remaining, it may eventually discharge.
Li-ion battery degradation over time
From the summary table below it is understood that it is necessary avoid leaving a lithium ion battery with full charge: with the 40% of charge a lithium battery will last much longer than a lithium charge 100%. The more charged the battery, the greater its natural degradation over time, even without using it.
BMS update and SOH electric car battery "restoration".
To remedy this inevitable loss of capacity over time, almost all manufacturers of electric car batteries keep a reserve of kWh that is not used. After a certain period when the SOH (residual autonomy and state of health) of the battery drops below a defined threshold (e.g. 75%) by reprogramming the BMS (electronic control and management system integrated in the battery) restore the battery to 100% like new condition.
If you have arrived here at the bottom you should have understood that the Electric car batteries don't last a lifetime, but they slowly lose their ability to store energy over time even if unused.
4 factors that cause an electric car's lithium battery to lose capacity
The main factors that cause loss of capacity and end of life of batteries on which battery manufacturers work to improve their efficiency.
- mechanical degradation of the electrodes or pressure loss in the bag cells. Careful cell design and correct choice of electrolyte additives reduce this phenomenon.
- growth of SEI on the anode, which increases internal resistance. The growth of this layer causes most lithium graphite batteries to lose efficiency when the charge voltage is kept below 3,92V per cell. Also in this case the use of additives in the electrolyte slows down the degradation.
- formation of electrolyte oxidation (EO) at the cathode, which leads to a sudden loss of battery capacity. It is caused by cell voltages above 4,10V and high temperatures.
- Lithium “plating” on the anode caused by high charging frequencies.
Battery life, Toyota, Tesla, the warranty how long it lasts
Tesla Roadster battery, duration and warranty
The new Tesla models are based on a precise design philosophy, namely the oversizing of the battery pack for reduce their stress during operation. This approach denotes that Tesla has focused its efforts on obtaining a high energy density for maximum autonomy. The downside to oversizing is a higher energy consumption in movements essentially due to the greater weight of the vehicle and a higher cost of the battery.
The duration of the TESLA WARRANTY for battery and motor varies according to the model: they are covered for a period of time and a maximum number of kilometers (whichever occurs first).
8 years or 240.000 km to Model S e Model X
8 years or 160.000 km Model 3 and Model Y Standard o Standard Range Plus
8 years or 192.000 km su Model 3 e Model Y Long Range o Performance
The guarantee intervenes when the battery capacity falls below the threshold of 70%.
Tesla offers a new vehicle warranty for 4 years or 80.000 km whichever comes first. The costs for the repair of defective parts and malfunctions are covered, such as the cost of labor and materials including spare parts.
Toyota on Prius replaced the previous generation Ni-MH batteries with new lithium-ion, Li-ion, guaranteed for 8 years or 300.000 km.
For the life of a battery Tesla set a period of 8 years for a mileage of 200.000 km on batteries a 60 kWh: for those from 70 kWh there are no travel limits.
Nissan, Tesla, Mitsubishi, BMW, Renault electric car battery warranty
8 years or 160.000 km is the guarantee for Nissan Leaf, by Mitsubishi for Outlander Phev, same period but reduced from BMW on the i3 and i8 at a mileage of just 100.000 km.
Renault on rental batteries guarantees the efficiency always higher than the 75% of the initial capacity: if it drops, it is "restored" to 100% with a BMS update or, in the event of a fault, repaired and replaced quickly.
Everlasting Renault, in the case of a purchased battery, ensures the battery's charge capacity ZOE of at least 66% of its initial level for at least 8 years or 160.000 km until the first of the 2 terms is reached.
Mercedes battery warranty 6 years or 160.000 km
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