What Are EV Fast Chargers & Do They Damage Battery Capacity?
Fast charging technology makes it extremely convenient for EV owners to recharge their vehicles while on the move. It’s this flexibility of being able to cover great distances with minimal charging times that made them adequate at replacing petrol powered ones.
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There are three levels of charging. Level 1 or slow charging uses the 240V power outlet in your home. It usually requires many hours to recharge the battery. Level 2 is AC fast charging and utilizes more powerful hardware using either a single-phase AC or 3-phase power outlets that can deliver up to 22kW to compatible vehicles.
Lastly, there’s Level 3 DC Fast Charging that can supply up to a demonstrated 900kW of power to compatible vehicles. Instead of requiring several hours like Level 2, it can charge an EV’s battery in about half an hour. But is this good for long term battery health?
An EV battery pack consists of hundreds if not thousands of individual cells. Each of them consists of an anode, cathode, electrolyte, and a separator. When charging the battery with an external power source, the electrons flow through the external circuit from the cathode and head towards the anode.
The Lithium-ions that have lost said electron, leave the cathode and flow back through the electrolyte to the anode. During the fast-charging process, this happens at a very rapid rate, which produces a higher amount of heat.
If not managed properly, that could be detrimental to overall battery health. However, modern EVs have an effective battery management system (BMS) that manages the charging process. It does everything from managing charging rates to thermal regulation.
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The onboard cooling/heating system kicks in when needed to manage battery temperature to ensure that it’s kept within the optimal range. Despite this, resorting to DC fast charging often can still induce heating issues that cause long term damage, which affects overall range.
A study conducted by the Idaho National Laboratory on four, 2012 Nissan Leaf EVs, discovered that fast charging does cause damage to batteries over prolonged use. There’s also an increase in degradation for EVs that used DC charging instead of the level 2 AC charger after about 80,000km of testing.
The vehicles that used DC fast charging, were charged twice a day at a high rate, which is twice as often as recommended by manufacturers. They were driven and charged throughout the year in a city with a very hot climate, which represents an extreme scenario for any EV.
The noticeable difference in charge capacity between level 2 AC and DC Fast Charging was noticeable only when mileage hovered close to the 50,000km mark. That said, DC fast charging did lose more capacity versus the control vehicles, but the difference was small relative to total capacity loss.
Overall, the test showed that vehicles that used level 2 AC fast charging lost about 24% of their overall capacity and ones that used DC fast charging lost less than 28%. The study also stated that the hot climate may have accelerated the overall degradation of their test vehicles.
