04. Charging Methods:
Li-ion batteries in common with all other batteries face an interesting problem. This is their charging time. As the energy density of Li-ion batteries increases their standard charging time increases as well. People are not known for their patience especially in developed, populated cities where most of the world’s population live. In order to counter the ever increasing charging time due to the increasing energy density in electrical / electronic appliances, phones, tools, cameras & especially electric vehicles, manufacturers have had to find ways to shorten the charging time. They have most often achieved this by increasing the amount of amps of electrical energy (electrons) that a battery charger sends to a battery.
There are typically 2 charging methods for Electric Vehicles Regenerative Braking and an External Charger.
Regenerative Braking (Regen)
Regen is when an EV uses its electric mort to convert its original kinetic energy back into electricity by working in reverse and thus decelerating the EV. This way the kinetic energy is not lost as heat in the EVs brake pads which in turn adds some mileage to the EV and reduces the wear and tear of the car’s brake pads. This effect is discussed by David Drive Electric[1]. Each time an EV slows down using regen it converts about 60-70% of the kinetic energy back to electricity[2]. The rest is lost as friction due to aerodynamics, tyres on road and some other losses during the regeneration process.
A very clear explanation of how regen works is also found as a youtube video on the The Fast Lane Car[3] channel. This video demonstrates how much mileage and electrical power, regenerative braking can give back to a car. It shows Roman & Tommy Mica doing a regenerative braking comparison between a Tesla Model 3 (All-Wheel Drive) and a Nissan Leaf Plus (Extended Range) in a 154.2 Mile (248.2Km) round trip up a 77.1 Mile (124.1Km) one way trip up a mountain with an elevation difference of 6,500Ft (1,981m). The Tesla was charged at 236Mi (379Km) range which is the Nissan Leafs max range. After their first 77.1 Mile (124.1Km) trip the Tesla had 36% battery left and 112Mi (180Km) traveling miles left, while the Nissan had 46% battery left and 80Mi (128Km) traveling miles left (running time in video 6:25 to 22:24). After their second 77.1 Mile (124.1Km) trip the Tesla had approximately 34% battery left and 83Mi (133Km) traveling mile left while the Nissan had 29% battery left and 84Mi (135Km) traveling miles left (running time in video 23:40 to 34:41).
As shown in table above regenerative braking can give back 1-2Mi (2-4Km) to a car after a 154.2Mile (248.2Km) round trip up a mountain.
The amount of regenerative braking that a car can do is restricted by the speed at which the car’s batteries can be charged safely[4]. As mentioned earlier batteries do not charge rapidly whereas ultracapacitors do. The constant increase in energy density of ultracapacitors combined with ever more effective regenerative braking is what makes them the ultimate allies in the historic EV battery struggle with range.
External chargers
Where and how charging stations can be installed and how many and at what frequency they can be found are further issues for EVs. External chargers, where an EV plugs into[5] an external power supply, have 3 charging speeds Slow, Fast and Rapid or Ultra Rapid[6].
Slow charging:
Slow charging uses approximately 06 to 13A at 230V AC giving approximately a 3 to 6 kW charging speed. It charges an empty EV battery in about 8 to 12+ hours. This is the sort of charging you would get if you plugged a car directly to a regular or heavy household wall power socket.
Fast charging:
Fast charging uses approximately 13 to 70A to usually at 240V AC giving approximately a 7 to 22kW charging speed. This method will charge an empty EV battery in about 3 to 8 hours. For fast charging a dedicated circuit and appropriate cabling is required if charging at home.
Rapid or Ultra Rapid charging:
Rapid or ultra rapid charging is achieved at a charging station with special cables because of its use of extremely high power 43 to 350 or 400 kW. This is done using direct current (DC) electricity which bypasses the cars alternate current (AC) to DC converter which is normally used for slow or fast charging. Ultrarapid charge goes directly to the car’s DC battery packs thus doing away with the time consuming and heat producing power conversion. With rapid charging an empty EV battery can be charged in about an hour or less.
Rapid charging can be achieved at 43kW AC by using 3-phase 240V and approximately 60A electricity.