Rules govern every aspect of our lives, from paying taxes to wearing pants and not driving on the sidewalk. If you own an electric vehicle, it’s important to understand the “80% rule” because it influences both charging performance and battery longevity. Charging an EV to 80% most of the time is recommended as charging rates slow down significantly past this mark, and keeping the battery below 100% improves its long-term health.
What does this mean in practical terms? For example, the Hyundai Ioniq 5 with the long-range battery option can DC fast charge from 10 to 80% in 18 minutes, but it takes an additional 32 minutes to reach 100%. This is because charging is not linear and the rate slows down as the battery becomes fuller. A good analogy for this is comparing batteries to theater seating, where finding a seat becomes progressively more difficult as the theater fills up.
It’s crucial to be aware of the “80% rule” when on long-distance drives in an EV. When it’s time to recharge, it’s often more efficient to stop at 80% rather than waiting for a full charge. For instance, if your EV has a range of 300 miles when fully charged, it can cover approximately 240 miles with an 80% charge. If the 0-80% recharge time is 40 minutes, you can get back on the road in a little over half an hour, whereas fully replenishing the battery could take an additional 90 minutes to go from 80 to 100%.
In the time it takes to gain that extra range, you could cover a significant distance and be near another charging station, making stopping at 80% the more sensible option (although this is something you need to decide for yourself). However, there are situations where waiting for a full charge makes sense, such as when there are large distances between fast chargers or in adverse weather conditions.
Another reason to avoid fully charging the battery is to preserve its longevity. Just like other electronic devices, batteries deteriorate more quickly when kept at full capacity. Car manufacturers even recommend limiting how much you charge, and some vehicles have infotainment systems that allow you to set your preferred charge level.
While it’s possible to charge your EV to 100%, charging to a lower percentage is advisable for optimal battery life in the long run, similar to changing the engine oil more frequently in a traditional vehicle. Finally, it’s important to understand that the time it takes to charge an electric car is influenced by many nuanced variables, and providing a precise answer is challenging. However, reliable guidelines can be provided to help with estimating charging times.
This question is on the minds of every electric vehicle (EV) shopper or owner. Although there’s no simple answer, understanding the various factors involved will help you estimate the time needed to charge an EV.
Determining the exact charging time for an electric car is like asking, “How long does it take to cross the country?” The answer depends on whether you’re traveling by plane or on foot. Charging time depends on a multitude of variables, some of which are quite subtle; even the length of the charging cable can have an impact, making it impossible to provide an exact answer. However, we can provide reliable guidelines.
Setting aside the more minute variables, there are three main factors that affect EV charging time: the power source, the capacity of the vehicle’s charger, and the size of the battery. Ambient conditions generally play a smaller role, though extreme cold or hot weather can significantly increase charging time.
Factors affecting charging time:
Charger Level
Let’s start with the power source. Not all electrical outlets are the same. A standard 120-volt, 15-amp outlet in a kitchen can be compared to a 240-volt outlet that powers an electric dryer as a squirt gun is to a garden hose. In theory, all electric vehicles can charge their large batteries from a standard kitchen outlet, but it would be like trying to fill a 55-gallon barrel with a squirt gun. Charging an EV battery using a 120-volt source—these are classified as Level 1 according to SAE J1772, a standard used by engineers to design EVs—can take days, not hours.
If you own or plan to own an EV, it’s wise to consider installing a 240-volt Level 2 charging solution in your home. A typical Level 2 connection is 240 volts and 40 to 80 amps. Even with fewer amps, it’s still considered Level 2, but an 80-amp circuit will maximize most EV’s onboard chargers (more on those in a minute). If you’re not maximizing the effectiveness of the vehicle’s onboard chargers, a lower-than-optimal power source will essentially prolong the charge time.
For the fastest possible charging, you’ll want to connect to a Level 3 connection, often referred to as a DC fast-charger. These are like filling the barrel with a fire hose. A lethal current of DC power is pumped into the car’s battery, quickly adding miles of range. Tesla’s V3 Superchargers provide up to 250 kW, and Electrify America’s fast chargers offer up to 350 kW of power.
However, like all charging, the flow is reduced when the vehicle battery’s state of charge (SoC) is nearing full. Different vehicles have varying abilities to accept DC charging. For example, the Porsche Taycan can charge at up to 320 kW, while a Nissan Ariya can only manage 130 kW.
Using a Fast-Charger
In general, when an EV battery’s SoC is below 10 percent or above 80 percent, a DC fast-charger’s charging rate significantly slows down. This optimizes battery life and reduces the risk of overcharging. This is why manufacturers often claim that fast-charging will get your EV’s battery to “80 percent charge in 30 minutes.” Some vehicles have a battery preconditioning procedure that ensures the battery is at the optimal temperature for fast charging while en route to a DC fast-charger. As long as you use the in -car navigation system to get you there, that is.
Maximum Charging and Driving Range
The last 20 percent of charge may double the time you’re connected to the fast-charger. Fully charging the battery through a DC charger can be time-consuming, so these units are best used on days when you’re traveling a long distance and need additional electricity to reach your destination. Charging at home overnight, sometimes called top-up charging, is a better solution for getting the required power for daily, local driving.
Battery Size
As manufacturers continue to seek greater range, the battery capacity of some EVs has grown to extreme levels, while others are focusing on increased efficiency. This significantly affects charging time. If we increase our barrel to an 85-gallon unit, it will still take longer to fill even with a fire hose, compared to the smaller 55-gallon barrel. For example, filling the 205.0-kWh battery of a GMC Hummer EV, even with its ability to intake 350 kW, requires exponentially more time than filling the 112.0 -kWh pack of a Lucid Air Grand Touring, even if the charging rate is similar. The Lucid can travel over 40 percent further on a single charge despite having a 93.0-kWh smaller battery pack than the Hummer. Efficiency, indeed.
Certainly, manufacturers will eventually settle on a single metric for expressing charge times. But for now, it’s important to understand that charging an EV’s battery still takes much longer than refueling a gas-powered car’s tank, regardless of how or where it’s done.
Charger Capacity
Many people mistakenly believe that the device connected to an electric car is the “charger.” However, the vehicle actually contains a battery charger that converts AC electricity from the wall into DC electricity in order to charge the battery. Onboard chargers gradually supply power to the battery pack and have their own power ratings, usually measured in kilowatts. For example, if a car has a 10.0-kW charger and a 100.0-kWh battery pack, it should, theoretically, take 10 hours to charge a fully depleted battery.
To calculate the optimal charging time for a specific EV, you divide the battery capacity in kilowatt-hours by the power rating of the onboard charger and then add 10 percent, since there are losses during charging. This assumes that the power source can fully utilize the vehicle’s charger.
Typical onboard chargers are usually at least 6.0 kilowatts, but some manufacturers offer almost double that amount, and some models have more than triple the typical figure. For instance, the current Tesla Model 3 Performance is equipped with an 11.5-kW charger, which can fully utilize a 240-volt, 60-amp circuit to charge its 80.8-kWh battery, while the rear-wheel-drive Model 3 comes with a 7.6-kW charger.
Based on the recharge-time calculation, it would take nearly the same amount of time to charge the batteries of the two cars, even though the Performance model’s battery is approximately 30 percent larger. A well-paired electricity source and onboard charger allow you to plug in your EV at home with a nearly depleted battery and wake up to a fully charged vehicle in the morning. You can also find estimated recharge times on some EV manufacturers’ websites.
In conclusion, there is a wide range of possibilities when determining the duration of an EV’s charging. In testing, we have seen DC fast-charging times as short as 25 minutes (from 10 to 90 percent) in a Porsche Taycan prototype, and as long as two hours in a GMC Hummer EV SUV, with the average charging time being just under an hour.
For Level 2 connections, the variation in charging time is much greater. The Lucid Air Pure takes slightly over five hours to charge from zero to 100 percent, while the Nissan Ariya takes over 13 hours, with the average falling in the seven-to- eight-hour range.
Battery electric vehicles have significantly increased their range over the years. From 2017 to 2021, the average range on a single charge rose from 151 miles to 217 miles, and continues to increase further. There is even a model in the US that can travel 520 miles on a full charge. Keep in mind that the range on a full charge assumes the battery is used from 100% down to 0%, but it is generally not recommended to use an EV battery at its extreme limits.
Is it distress to charge an EV battery pack to its full capacity, and if so, what are the potential consequences? On the other hand, is it harmful to deplete the battery completely? If so, what is the best strategy for charging your EV’s battery? Here is what you need to know.
Charging the battery to full capacity can be problematic. The battery packs in electric cars typically utilize lithium-ion chemistry. Similar to other devices using Li-Ion batteries, such as cell phones and laptops, charging the battery to 100% capacity can either negatively impact the state of charge (SoC) or lead to a catastrophic failure.
Thankfully, catastrophic failures are extremely rare, but battery pack degradation is much more likely. Continuously charging to 100% capacity encourages the growth of lithium metal tendrils called dendrites, which can cause a short circuit. More commonly, the lithium ions fall out of circulation when they become involved in side reactions within the electrolyte, often due to the increased temperature generated when a battery is charged to its extreme capacity.
Charging an EV to 100% is not always discouraged. If you need to embark on an extended trip with your EV or do not have access to a charging station for an extended period, occasionally charging your EV to 100% is unlikely to cause any significant issues. Problems arise when you consistently recharge to 100%.
A full charge may not be what it seems. Did you know that some automakers are incorporating a buffer into their EVs to help maintain a healthy SoC for as long as possible? This means that when the battery monitor displays a 100% charge, the battery pack is not actually reaching the limits that could impact the battery’s health. This reserve or buffer helps mitigate potential degradation, and most automakers are likely to implement this design to keep their vehicles in the best condition possible.
Discharging a battery completely can also be harmful. At the other end of the spectrum, it is equally unhealthy, or possibly even more so, for an electric vehicle (EV) battery to be completely discharged to 0%. If it were to reach 0 %, the battery would need careful recovery. Fortunately, an EV’s battery management system, or BMS, is designed to maintain a 5 to 10% buffer to prevent complete discharge from normal use. The exception would be if the car remains idle and the battery pack self-discharges, but that would theoretically take weeks or months.
Reducing discharge to a minimum is the best approach. While regularly charging to the extremes – either all the way to 100% or down to 0% – is not recommended, the actual lifespan depends on much less demanding use. Studies are being conducted to determine the impact of the depth of discharge on battery health, and the findings are compelling.
In general, consistently discharging a battery by more than 50% of its capacity reduces the expected number of cycles it will last. For instance, charging the battery to 100% and discharging it to less than 50% will diminish its lifespan, as will charging the battery to 80% and discharging it to less than 30%.
How does the depth of discharge (DoD) affect battery life? A battery cycled to 50% DoD will maintain its capacity four times longer than one cycled to 100%. Since EV batteries almost never fully cycle – considering the buffers on the extremes – the real-world impact is likely less, but still substantial.
How should you charge your EV battery to extend its life? It is advisable to keep an EV’s charge above 20% when possible, both to preserve its battery health and to avoid range anxiety. Just like driving a gasoline-powered car with less than a quarter tank, you want the assurance that you’ll be able to refuel before running out.
Many experts recommend keeping the EV’s battery pack between 30% and 80% of its full charge to maintain its State of Health, or SoH. The CEO of a major EV carmaker has suggested that recharging to 90 or 95% of capacity is not an issue for maintaining the battery’s SoH. As long as the State of Charge (SoC) is not maintained at either extreme for an extended period, degradation should be prevented from occurring at an accelerated level.
The more critical issue tends to be the depth of discharge. Whether charging to 60%, 80%, or even 95%, it is best to keep the DoD as low as possible, and it is certainly preferable to keep it below 50% DoD .
By avoiding regular charges to 100% and always avoiding complete discharge to 0%, as well as maintaining less than 50% DoD, you will keep your EV’s battery operating at its best for years to come with minimal impact on SoH.
Charging and discharging batteries involve a chemical reaction, and while Li-ion is claimed to be the exception, battery scientists discuss energies flowing in and out of the battery as part of ion movement between the anode and cathode. This claim has merit, but if the scientists were entirely correct, the battery would last indefinitely. They attribute capacity fade to ions being trapped, but as with all battery systems, internal corrosion and other degenerative effects, also known as parasitic reactions on the electrolyte and electrodes, still play a role .
The Li-ion charger is a device that limits voltage, similar to the lead acid system. The differences with Li-ion lie in a higher voltage per cell, stricter voltage tolerances, and the absence of trickle or float charge at full charge. Unlike lead acid, which offers some flexibility in terms of voltage cut off, manufacturers of Li-ion cells are very strict about the correct setting because Li-ion cannot accept overcharge. The so-called miracle charger that promises to prolong battery life and gain extra capacity with pulses and other gimmicks does not exist. Li-ion is a “clean” system and only takes what it can absorb.
Charging Cobalt-blended Li-ion
Li-ion batteries with traditional cathode materials of cobalt, nickel, manganese, and aluminum usually charge to 4.20V/cell. The tolerance is +/–50mV/cell. Some nickel-based varieties charge to 4.10V/cell; high-capacity Li-ion batteries may go to 4.30V/cell and higher. Increasing the voltage boosts capacity, but going beyond specification stresses the battery and compromises safety. Protection circuits integrated into the pack prevent exceeding the set voltage.
Figure 1 illustrates the voltage and current pattern as lithium-ion goes through the stages for constant current and topping charge. Full charge is achieved when the current drops to between 3 and 5 percent of the Ah rating.
Li-ion is fully charged when the current decreases to a set level. Instead of trickle charge, some chargers apply a topping charge when the voltage drops.
The recommended charge rate for an Energy Cell is between 0.5C and 1C; the complete charge time is about 2–3 hours. Manufacturers of these cells recommend charging at 0.8C or less to prolong battery life; however, most Power Cells can handle a higher charge C-rate with minimal stress.
For certain Li-ion packs, when they reach full charge, there could be a temperature rise of approximately 5ºC (9ºF). This increase may be due to the protection circuit and/or a higher internal resistance. If the temperature rises more than 10ºC (18ºF) at moderate charging speeds, it is advisable to stop using the battery or charger.
A battery is considered fully charged when it reaches the voltage threshold and the current drops to 3 percent of the rated current. It is also considered fully charged if the current levels off and cannot decrease further, which might be caused by elevated self-discharge.
Although increasing the charge current speeds up reaching the voltage peak, the overall time to reach the saturation charge will be longer. While Stage 1 is shorter with higher current, the saturation during Stage 2 will take longer. Charging at a high current, however, will quickly fill the battery to about 70 percent.
Unlike lead acid batteries, Li-ion batteries do not require being fully charged, and it is not recommended to do so, as high voltage stresses the battery. Opting for a lower voltage threshold or eliminating the saturation charge prolongs battery life but reduces the runtime Consumer product chargers prioritize maximum capacity and typically cannot be adjusted, hence prioritizing extended service life may be considered less important.
Some inexpensive consumer chargers may use a simplified “charge-and-run” method, charging a lithium-ion battery in one hour or less without going to the Stage 2 saturation charge. When the battery reaches the voltage threshold at Stage 1, it shows as “Ready,” with the state-of-charge (SoC) at about 85 percent, which may be adequate for many users.
Certain industrial chargers intentionally set the charge voltage threshold lower to extend battery life. A table illustrates the estimated capacities when charged to different voltage thresholds with and without saturation charge.
When put on charge, the battery’s voltage quickly rises, similar to lifting a weight with a rubber band, causing a lag. The capacity will eventually catch up when the battery is almost fully charged. This behavior is typical of all batteries, with the rubber -band effect larger becoming with higher charge current or when charging a cell with high internal resistance, especially in cold temperatures.
Measuring the open circuit voltage (OCV) after the battery has rested for a few hours is a better indicator of state-of-charge (SoC) than attempting to estimate SoC by reading the voltage of a charging battery. For smartphones, laptops, and other devices, SoC is often estimated by coulomb counting. (See BU-903: How to Measure State-of-charge)
Li-ion batteries cannot absorb overcharge, so the charge current must be cut off when fully charged. Continuous trickle charging would cause metallic lithium plating and compromise safety. To minimize stress, keep the lithium-ion battery at the peak cut-off as short as possible.
After the charge is terminated, the battery voltage begins to drop, alleviating the voltage stress. Over time, the open circuit voltage will settle to between 3.70V and 3.90V/cell. Note that a Li-ion battery that has received a fully saturated charge will keep the voltage elevated for longer than one that has not received a saturation charge.
In cases where lithium-ion batteries must be left in the charger for operational readiness, some chargers apply a brief topping charge to compensate for small self-discharge. The charger may kick in when the open circuit voltage drops to 4.05V/cell and turn off again at 4.20V/cell. Chargers made for operational readiness often let the battery voltage drop to 4.00V/cell and recharge to only 4.05V/cell instead of the full 4.20V/cell to reduce voltage-related stress and prolong battery life.
Battery manufacturers against parasitic loads while charging as they induce mini-cycles. This cannot always be advised avoid, such as when a laptop is connected to the AC main during charging, causing the battery to be charged to 4.20V/cell and then discharged by the device, leading to high stress levels because the cycles occur at the high-voltage threshold, often also at elevated temperature.
For optimal charging, portable devices should be turned off during charge to allow the battery to reach the set voltage threshold and current saturation point unhindered. A parasitic load during charging confuses the charger, preventing the current in the saturation stage from low dropping enough and prompting a continued charge even when the battery may be fully charged.
Charging Non-cobalt-blended Li-ion
The traditional lithium-ion has a nominal cell voltage of 3.60V. However, Li-phosphate (LiFePO) stands out with a nominal cell voltage of 3.20V and charging to 3.65V. A relatively new addition is the Li-titanate (LTO) with a nominal cell voltage of 2.40V and charging to 2.85V. Special chargers are required for these non cobalt-blended Li-ions, as they are incompatible with regular 3.60-volt Li-ion. It is vital to correctly identify the systems and provide the appropriate voltage charging. Failure to do so would result in a regular charger not delivering sufficient charge to a 3.60-volt lithium battery, and a regular charger overcharging a Li-phosphate battery.
Overcharging Lithium-ion
Lithium-ion can operate safely within designated operating voltages. However, it becomes unstable if charged to a voltage higher than specified. Charging a Li-ion designed for 4.20V/cell to above 4.30V can lead to metallic lithium plating on the anode, instability in the cathode material, leading to the production of carbon dioxide (CO2). As a result, the cell pressure rises, triggering the current interrupt device (CID) responsible for cell safety to disconnect at 1,000–1,380kPa (145–200psi ). If the pressure continues to rise, the safety membrane on some Li-ion cells bursts open at about 3,450kPa (500psi), potentially leading to venting with flame.
Venting with flame is associated with elevated temperature. A fully charged battery has a lower thermal runaway temperature and will vent sooner than a partially charged one. Therefore, lithium-based batteries are safer at a lower charge, prompting authorities to mandate air shipment of Li -ion at 30 percent state-of-charge rather than at full charge.
The threshold for Li-cobalt at full charge is 130–150ºC (266–302ºF); nickel-manganese-cobalt (NMC) is 170–180ºC (338–356ºF), and Li-manganese is about 250ºC (482ºF). phosphate enjoys similar and better temperature stability than manganese.
Lithium-ion is not the only battery that poses a safety hazard if overcharged. Lead- and nickel-based batteries are also known to melt down and cause fire if improperly handled. Properly designed charging equipment is essential for all battery systems, with temperature sensing serving as a reliable watchman.
Summary
Charging lithium-ion batteries is simpler than nickel-based systems. The charge circuit is straightforward, and voltage and current limitations are easier to accommodate in comparison to analyzing complex voltage signatures that change as the battery ages. The charge process can be intermittent, and Li-ion does not need saturation like lead acid. This simplicity provides a significant advantage for renewable energy storage, such as solar panels and wind turbines, which may not always fully charge the battery. The absence of trickle charge further simplifies the charger, and equalizing charger is not necessary with Li-ion, unlike with lead acid.
Consumer and most industrial Li-ion chargers charge the battery fully and do not offer adjustable end-of-charge voltages that could prolong the service life of Li-ion by lowering the end charge voltage and accepting a shorter runtime. This is due to concerns that such an option would complicate the charger. However, there are exceptions with electric vehicles and satellites, avoiding full charge to achieve long service life.
Simple Guidelines for Charging Lithium-based Batteries:
Turn off the device or disconnect the load on charge to allow the current to drop unhindered during saturation. A parasitic load can confuse the charger. Charge at a moderate temperature, avoiding charging at freezing temperature. Lithium-ion does not require a full charge; a partial charge is preferable. Not all chargers apply a full topping charge, so the battery may not be fully charged when the “ready” signal appears. Discontinue using the charger and/or battery if the battery becomes excessively warm. Apply some charge to an empty battery before storing, with 40–50 percent State of Charge (SoC) being ideal.
The ultimate focus shifted to maximizing the energy density of Li-ion in 2006 when Li-ion unexpectedly disassembled in consumer products, leading to the recall of millions of packs. Safety gained attention, and with the growth of electric vehicles (EVs), longevity became crucial, prompting experts to explore why batteries fail.
While a 3-year battery life with 500 cycles is acceptable for laptops and mobile phones, the mandated 8-year life of an EV battery may seem long initially. However, it can still concern EV buyers, especially considering that the price of a replacement battery matches that of a compact car with an internal combustion engine. If the battery’s life could be extended to, say, 20 years, then driving an EV would be justified even with the high initial investment.
Manufacturers of electric vehicles opt for battery systems optimized for longevity rather than high specific energy. These batteries are generally larger and heavier than those used in consumer goods.
An extensive evaluation process is conducted on batteries selected for an electric powertrain, and Nissan opted for a manganese-based Li-ion for the Leaf EV due to its strong performance. To meet testing requirements, a rapid charge of 1.5C (less than 1 hour) and a discharge of 2.5C (20 minutes) at a temperature of 60°C (140°F) were mandated.
Under these demanding conditions, a heavy-duty battery is expected to experience a 10 percent loss after 500 cycles, equivalent to 1–2 years of driving. This mirrors the experience of driving an EV in extreme heat and still ending up with a battery that retains 90 percent capacity.
Despite meticulous selection and thorough testing, Nissan Leaf owners observed a capacity decrease of 27.5 percent after 1–2 years of ownership, even without aggressive driving. So, why did the Leaf experience such a significant capacity drop under protected conditions?
To gain a deeper understanding of the factors leading to irreversible capacity loss in Li-ion batteries, the Center for Automotive Research at the Ohio State University, in collaboration with Oak Ridge National Laboratory and the National Institute of Standards and Technology, performed detailed analyzes by dissecting failed batteries to identify potential issues with the electrodes.
By unrolling a 1.5-meter-long (5 feet) strip of metal tape representing the anode and cathode coated with oxide, it was revealed that the finely structured nanomaterials had coarsened. Further investigations showed that the lithium ions responsible for transferring electric charge between the electrodes had decreased on the cathode and become permanently lodged on the anode. tested, the cathode had a lower lithium concentration than a new cell, a situation that cannot be reversed.
For individuals investing in an electric vehicle (EV), taking care of the battery is essential to safeguarding their investment. Over recent decades, society has become increasingly reliant on battery-powered devices and equipment. From smartphones and earbuds to laptops and now EVs, they have become integral to our lives. However, it is crucial to pay extra attention and care when it comes to EV battery usage, as EVs entail a much larger financial investment and are intended to last much longer than smartphones or laptops.
While generally it is true that EV batteries require minimal maintenance for users, there are guidelines to follow to ensure the battery remains in good condition for an extended period.
Best Practices for Charging EV Batteries
Over time, it is advisable to minimize the frequency of charging an EV battery to prolong its longevity. Additionally, implementing the following EV battery care tips will help maintain the battery’s high performance.
Be Mindful of Charging Speed
Best practices for EV battery charging suggest that Level 3 chargers, which are commercial systems providing the fastest available charging speed, should not be heavily relied upon due to the high currents they generate, leading to elevated temperatures that strain EV batteries. On the other hand , Level 1 chargers are slow and inadequate for many drivers who rely on their EV for daily commutes. Level 2 chargers are more beneficial for EV batteries than Level 3 chargers, offering charging speeds up to 8 times faster than Level 1 systems.
Adopt the Same Approach for Discharging
While patience is required for EV charging, favoring a Level 2 charger over a Level 3 one, it is also important to discharge the battery methodically. To prevent unnecessary battery degradation, avoid aggressive driving or excessive speeding, and instead, try to coast more and brake less to extend the battery’s charge. This practice is similar to the approach popular with hybrid vehicles, resulting in less energy consumption and a longer-lasting battery. Furthermore, it helps preserve the brakes, leading to cost savings.
Impact of High and Low Temperatures on EV Battery Care
Whether the EV is parked at work or home, minimize the exposure to extremely high or low temperatures. For instance, if it’s a scorching 95℉ summer day and there is no access to a garage or covered parking, try to park in a shaded area , or connect to a Level 2 charging station so the vehicle’s thermal management system can help safeguard the battery from heat. offline, if it’s a chilly 12℉ winter day, attempt to park in direct sunlight or connect the EV to a charging point.
Following these recommended best practices for EV battery care does not mean you cannot store or operate the vehicle in very hot or cold locations, but repeated exposure to such conditions over an extended period can expedite battery degradation. While battery quality continues to improve due to advancements in research and development, battery cells do deteriorate, resulting in reduced driving range as the battery degrades over time. Therefore, a good guideline for EV battery care is to aim to store the vehicle in mild weather conditions.
Monitor Battery Usage – Prevent a Completely Drained or Fully Charged Battery
Whether you frequently drive or your EV goes long periods without charging due to minimal use, try not to let your battery reach 0% charge. The vehicle’s battery management systems typically shut off before it reaches 0%, so it’s important not to go beyond that point.
Additionally, avoid charging your vehicle to 100% unless you expect to need a full charge that day. This is because EV batteries experience more strain when near or at full charge. For many EV batteries, it’s advisable not to charge above 80%. With many newer EV models, you can easily set a charging maximum to protect your battery’s lifespan.
Consider Your Usage and Range
It’s not necessary to charge your electric car daily. The ideal frequency varies based on your lifestyle, your vehicle, and how often and how far you drive, as well as the battery’s range. For everyday urban use involving short trips of about 30 kilometers per day, daily charging isn’t required. In fact, it’s recommended not to charge your car too frequently.
The key is to maintain an optimal charge: between 20% and 80% for the lithium-ion batteries found in most electric cars. To preserve your battery, it’s best to avoid the extremes: strive to keep your battery’s charge above 20% and below 80%. This should guide the frequency and duration of charging for your electric car.
Nevertheless, a full charge will ensure that you can cover long distances. We suggest charging your car up to 100% with a normal or accelerated charge (3-phase charging at 22 kW) to minimize the use of fast charging stations. These stations should only be utilized when absolutely necessary as they can gradually and prematurely damage the battery cells. Also, remember to unplug your vehicle when it has reached full charge to prevent unnecessary heating of the battery.
4 Recommendations for Optimal Charging
If you have an electric charging point at home, consider charging your car during off-peak hours. Using a 7.4 kW (32 A) charging point will allow you to charge your car up to three times faster than with a wall outlet (8 A ), while limiting your energy consumption at a lower cost. In France, there is even a new law allowing the installation of a charging point in the parking lot of your apartment building.
Adopt energy-efficient driving habits to extend your range. Drive at a moderate speed: 110 km/h on highways and 100 km/h on major roads.
Your vehicle’s weight affects its range. It’s advisable to minimize the load in your car as much as possible; if you can travel without a roof box, your charge will last longer.
In the summer, we recommend allowing your battery to cool down before charging. In hot weather and during heatwaves, the battery may overheat and lose charge more rapidly. This preventive cooling helps preserve its capacity and range.
One of the initial questions people often ask when they get an electric vehicle (EV) is: when should I charge it? Unlike internal combustion engine (ICE) vehicles, where you can easily refuel at the nearest gas station, charging an EV takes longer and involves electricity. Using a Level 1 charger, which plugs into a regular 120-volt electrical outlet at home, will likely take several hours to fully charge your vehicle.
A Level 2 charger, commonly found in public charging stations, will probably take just a few hours to charge your battery. These chargers plug into the standard 240-volt circuit at homes and businesses. On the other hand, a Direct Current Fast Charger ( DCFC) will take less than an hour to fully charge your vehicle. However, plug-in hybrid EVs cannot use a DCFC. DC fast chargers use much more electricity than Level 1 and Level 2 chargers and require a 480-volt circuit.
The time it takes to fully charge your battery depends on factors such as the battery’s capacity, its initial charge level, and the type of charger used. But bear in mind another variable: the time of day when charging.
Why Does the Time of Day Matter?
While electricity may seem abundant when you simply plug in small appliances at home, it’s actually not infinite. Electricity is finite, and your local utility provider has a certain electrical capacity. When this capacity is reached, it may have to draw more power from elsewhere to accommodate all the electrical appliances and equipment. If more power is unavailable, this can lead to brownouts and/or blackouts. To help avoid overloading your local electricity provider, consider charging your vehicle during off-peak hours with a Level 2 charger.
On-Peak & Off-Peak Hours
On-peak hours refer to the time of day when the electrical grid is most active. During this time, more appliances and equipment are using electricity compared to other times of the day. The US Energy Information Administration (EIA) defines on-peak hours as the period from 7:00 am to 11:00 pm on weekdays. In contrast, off-peak hours are from 11:00 pm to 7:00 am on weekdays, as well as the entire day on Saturdays, Sundays, and holidays .
The EIA’s website explains that electricity consumption follows a daily cycle, with the highest demand occurring at some point during the day and the lowest demand generally around 5:00 am This variation in electricity demand is influenced by daily energy use habits and weather-related factors Off-peak hours typically occur during late evenings, overnight, as well as on weekends and holidays.
Is it advisable to charge your EV during off-peak hours?
There are benefits to charging your electric vehicle (EV) during off-peak hours, including potential cost savings and contributing to the management of electricity demand.
Charging your vehicle during off-peak hours may be more economical, as many utilities offer discounted electricity rates during this time. For instance, the Los Angeles Department of Water and Power provides a $0.025 per kilowatt-hour discount for electricity used to charge EVs during off-peak times. Numerous other power companies have adopted similar measures to encourage off-peak charging.
By choosing to charge during off-peak hours, you are helping to alleviate the strain on the electrical grid in your area and preventing potential overloads. This parallels the act of recycling, where an individual actively chooses to contribute to a larger cause.
How can you ensure that you are charging during off-peak hours?
If your charger does not have automated scheduling capabilities, you can simply plug in your car each night and unplug it in the morning to consistently charge your EV during off-peak hours. Alternatively, using a programmable “smart” charger allows you to set specific charging times, eliminating the need for manual intervention.
When should you charge your vehicle during on-peak hours?
While the general recommendation is to charge your EV during off-peak hours whenever possible, there are scenarios where charging during on-peak hours may be necessary or advantageous. For example, if your battery needs to be charged urgently, or if you have access to workplace or public charging stations during the day, it may be practical to charge your vehicle during on-peak hours.
Battery State of Charge
The State of Charge (SoC) of your battery can affect charging speeds. In electric vehicles equipped with lithium-ion batteries, charging speeds tend to be faster with lower State of Charge percentages compared to higher ones. Therefore, charging an EV from 0 to 80 percent may be quicker than charging it from 80 to 100 percent.
This variability in charging speeds is influenced by battery chemistry and also serves as a protective measure to prevent overheating and extend battery life. Some EV manufacturers advise against regularly charging their EVs above 80 percent.
Battery temperature is a key factor in charging speeds. Electric vehicle (EV) batteries function at their best around 20°C. Most EVs come with a Battery Management System (BMS) that monitors and adjusts charging based on temperature. If temperatures deviate significantly from 20°C, the BMS decreases charging speed to safeguard the battery.
Changes in seasons also affect charging durations. For instance, cold weather can lead to longer charging times, but pre-heating the car can expedite charging in colder conditions.
Charging in hot weather does not impact charge speeds as much as cold weather, but it can still present challenges. The primary concern is battery overheating. If there is a risk of overheating, the BMS system may decrease charging speeds and increase cooling to maintain optimal temperature levels.
Using the car while it charges
Using the car while it’s charging may impact the charging time, depending on how it’s used. While driving is not possible while the car is plugged in, remaining in the vehicle and using heating or air conditioning, the sound system, or lights, for example , can increase energy consumption and divert some energy from charging, thereby extending charging times.
Software or hardware issues
While most software updates can notably enhance electric car charging and increase charging speed, occasionally the opposite might occur. It can be challenging to uninstall updates in such cases, and the issue may need to be managed until the new software update resolves it.
On the hardware side, EV batteries may develop issues over time if not properly maintained. However, with a lifespan of up to 10-15 years, they can sometimes outlast the vehicle. Nevertheless, batteries age and lose some of their capacity over time. As they age, the resistance inside batteries also increases, reducing the power they can accept and slowing down the charging rate.
It’s important to note that EV batteries are often designed with excess capacity to combat aging.
How to increase charging speeds
To enhance the charging speed of your electric car, consider the following strategies:
- Optimize battery temperature: Pre-heating the battery or arriving at a charger with an optimal battery temperature can help increase charging speeds. Furthermore, consider parking your car in a temperature-controlled environment.
- Upgrade your charger: Transition from a level 1 charger to a level 2 charger for quicker charging. Level 2 chargers can provide significantly more kilometers of charge per hour, adding range to your car 3 to 5 times faster than level 1 chargers.
- Choose a mild temperature zone: Park your car in an area with mild temperatures before charging, as extreme cold or heat can impact charging speeds.
- Warm up batteries before fast charging: Warming up the batteries before fast charging can reduce charging time. However, this may not have an impact when using a level 2 charger.
- Future-proof your charging setup: Install a charger with higher capacity than what you currently need.
- Use heavier-gauge wire: When setting up a new circuit or pulling new wires for an EV charger, opt for heavier-gauge wire.
- Consider adjustable current chargers: Some chargers, like Tesla’s Wall Connector and ChargePoint’s Home Flex, have adjustable current settings. Although these chargers may be more expensive, they offer flexibility for future upgrades.
- Schedule charging during off-peak hours: Charging your electric car during off-peak hours can potentially increase charge speeds, as there is less demand on the electrical grid.
- Regularly maintain your EV and charger: Ensure that your electric vehicle and charging equipment are well-maintained to optimize charging efficiency.
Please remember the following information:
- Take care not to overcharge or fully discharge your battery. Keeping your battery charge within its capacity limits can help preserve its health and extend its lifespan.
- Extreme temperatures can impact battery health and performance. Adjust your charging habits based on the weather to optimize your EV’s battery condition and operation.
- Avoid leaving your EV with a fully discharged or fully charged battery for long periods, as it can harm the battery’s health.
- Using a suitable amperage charger is essential for safe and efficient charging, which can extend your electric vehicle’s battery lifespan.
- The capacity of an EV battery determines its driving range. Higher capacity means more convenience, flexibility, and reduced range anxiety for EV owners.
- It’s vital to consider responsible recycling of electric car batteries to recover valuable materials and minimize environmental impact.
Several factors affect the degradation of EV batteries over time, including temperature, charge level, charge rate, number of charge cycles, battery chemistry, and storage conditions.
Understanding and managing these factors can maximize your EV battery’s life and maintain optimal performance throughout the vehicle’s lifespan. Regular maintenance, proper charging practices, and avoiding extreme conditions can all prolong the health and efficiency of an EV battery.
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