Fast charger VS home chargers
Home chargers charge the car with AC current which is converted to DC power by the vehicle itself. A Level 3 charger feeds straight DC power to the car, allowing the charger to recharge the car at a more rapid speed. Most electric cars are charged at home, but if an EV owner finds the state of charge indicator getting lower and lower while he is driving, a DC fast charging station can come in handy.
You may charge an EV’s battery up to 80 percent of its capacity in around 30-60 minutes with a public “Level 3” DC fast charging station. Different electric vehicles with different battery capacities need different time to recharge the electric vehicles. A fast-charging station is in constant communication with the electric vehicle to which it’s linked. The real power deliverable to the electric car depends on the power of the EVSE and how much the vehicle battery can handle which varies from one model to another. The outdoor temperature also plays a role. A cold battery gets recharged slower than a warm one does.
Is fast EV charging always so desirable?
Fast charging sounds fascinating. However, technically, fast charging does have a negative impact on the battery service life. Frequent fast charging, especially fast charging in very short time is not advocated. If you charge the electric car too fast, a bunch of lithium ions will come over altogether and get embedded in the negative electrode. When too many lithium ions get crowded at the negative electrode, they will combine with electrons to form lithium metal. Lithium metal will grow into dendrites, and dendrites will puncture the separator that separates the positive and negative electrodes, causing a short circuit accident. Even if things won’t get that serious, the battery’s service life will be shortened. So the impact to the battery’s service life is the main concern why we are against the theory “the faster charging, the better”.
What if we have to use fast EV charging stations?
Even if you want to fast charge the electric car, you should only choose fast charging for part of the charging journey where fast charging is more acceptable to the battery, not from the beginning to the end of the charging cycle.
How does the charging cycle work?
Once charging starts and the electric vehicle’s battery is warmed up, the flow of electric power typically increases to the vehicle’s maximum input. The charger will sustain this charging rate for as long as possible, though it may drop to a more moderate speed if the vehicle tells the charger to slow down so as not to compromise battery life. Once an EV’s battery capacity reaches a certain level, normally 80 percent, charging essentially will slow to a Level 2 operation, known as the DC fast charging curve. This charging curve moderates the impact of fact charging to the battery life.
Other things to avoid before choosing fast charging:
In addition to choose part of the charging journey for fast DC charging, do not fast charge the car when the battery is fully discharged. Fast charging will lead to polarization of the battery. Polarization of the battery will lead to cut-off voltage which is even more dangerous for the electric vehicle.
There are some problems to be solved when it comes to charging safety. However, according to the statistical data, the probability of an electric vehicle accident is about 0.9 in 10,000 while the probability of spontaneous combustion of a traditional fuel vehicle is 3 in 10,000.
Lastly, the charging station regulates the flow of electricity accordingly so as not to overwhelm the vehicle’s charging system and damage the battery. This said, electric vehicles are safer than fuel vehicles.
In a word, it’s better to charge with home chargers for the most of time for longer battery life and try to avoid full battery discharge before your use a fast charge point.