Yes, DC charging can be detrimental under the special circumstances described in the experiment of this article. Importantly, batteries prefer to run at comfortable temperatures, usually in the 70–80 degree Fahrenheit range (approximately 20–25 degrees Celsius). Fast charging provides more power, which can produce heat that “loads” the batteries more than charging from AC power. Some cars also have air conditioning to provide the optimum temperature for charging. Although heat stress has minimal effect on battery life over time, it is still recommended to rely on Level 2 for everyday charging [13].

Is using a DC fast charging station really bad for an electric car battery? 

Turns out, not as much as you might think. Read more about the experiment below.  However, frequent use of fast constant current charging can have a negative effect on battery performance and longevity. But often there are recommendations to minimize the use of fast constant current charging.

How does DC fast charging work?

Publicly available Level 3 DC fast charging stations can charge an electric car battery to 80 percent of its capacity in about 30–60 minutes. This depends on the vehicle and the air temperature (a cold battery charges more slowly than a warm one). Although most electric car charging is done at home, fast charging can also come in handy if the electric vehicle’s charge becomes too low, say, during a trip. Knowing the locations of Level 3 stations [22] is necessary for those going on long trips.

Availability of fast charging stations

Drive Electric Tennessee and TDEC are reportedly planning to increase the number of fast charging stations. The distance between stations is planned to be no more than 50 miles. This will help improve the availability of infrastructure in areas far from cities. It will also encourage more electric vehicles by 2028 to 200,000.

What connectors are used for fast charging?

U.S. electric vehicles use the SAE combination connector also known as CCS1. Most models from Asian automakers use the so-called CHAdeMO connector. And many Level 3 charging stations support both types.

Tesla uses its own connector to access its high-speed Supercharger network, which is limited to its own vehicles. However, Tesla owners can use other publicly available chargers through the adapter that comes with the car.

What are the differences between DC and AC when charging an electric car?

While home chargers use alternating current that is converted to direct current by the car, the Level 3 charger supplies direct DC power. This allows you to charge your car faster. The fast charging station is in constant communication with the electric vehicle to which it is connected. It monitors the vehicle’s charge level and delivers exactly as much power as the vehicle can handle, which varies from model to model. The station regulates the flow of electricity appropriately so that it does not overload the vehicle’s charging system or damage the battery.

Statistics say that most drivers drive no more than 50 miles in a day. Therefore, many people use fewer fast chargers enough to meet their charging needs.

Does the electric car battery charge evenly?

Once the vehicle’s battery starts charging and warms up, the kilowatt flow usually increases to the maximum power consumption of the vehicle. The charger will maintain this rate as long as possible, although it may drop to a more moderate rate if the car tells the charger to slow down so as not to reduce battery life. Once an electric car’s battery reaches a certain level of its capacity, usually 80 percent, charging slows significantly to Level 2. This is known as the DC fast charging curve.

Is a large number of kilowatts of EVSE harmful to the battery?

You can increase kilowatts, but not every vehicle will benefit from more power for a while. Most vehicles on the road today cannot accept the 350 kilowatts that are available at some electric vehicle charging stations [22]. Each vehicle’s charging rate is limited by battery voltage and allowable amperage.  350 kilowatts is the way to go for future charging stations, but 125 kilowatts is more than enough for today’s electric vehicles.

Can frequent fast charging damage my battery?

Lithium-ion batteries, which are commonly used in hybrid and electric cars, deplete over time, just like any other form of battery. And while laptop and cell phone batteries can be damaged if they are constantly charged at high power, electric car batteries are not.

This is because manufacturers have built-in safety systems to prevent damage from frequent use of fast or rapid charging. For example, the charge rate can be automatically reduced if the car detects that too much power is being applied to the battery too often.

The ability of an electric vehicle to accept higher charging currents is affected by battery chemistry. The generally accepted industry consensus is that faster charging will increase the rate at which an electric car’s battery capacity decreases. However, a study showed that although an electric car’s battery will wear out faster if it is only charged with Level 3 (which is almost never the case), the difference is not particularly noticeable.

The point of the experiment 

The experiment was conducted by the INL team. The test involved two pairs of 2012 model year Nissan Leaf electric cars, which were driven and charged twice a day. The first pair was charged through Level 2 AC chargers at 240 volts [13] , similar to those used in private homes.  The second pair was charged with direct current at a Level 3 station [22]. They traveled the same distance along the same route for a year. They were tested under the same conditions: their climate control systems were set to the same temperature, and all four cars were driven by the same team of drivers. The cars’ battery capacity was tested at 10,000-mile intervals.

After driving all four test cars 50,000 miles, the Tier 2 (AC) cars lost about 23 percent of their original battery capacity. Tier 3 (direct current) cars lost about 27 percent. The 2012 Leaf had an average range of 73 miles, which means these numbers represent a difference of only three miles without recharging.

Conclusions

Charging with direct current can affect the battery life of an electric car. In the experiment described, in the article, it is 4%.  However, this effect is minimal, especially if it is not the main charging source. So by understanding how to choose EVSE for an AC home you can extend the battery life of an electric car.