Unlike vehicles powered by fossil fuels, BEVs are most commonly and conveniently charged from the power grid overnight at home, without the inconvenience of having to go to a filling station. Charging can also be done using a street or shop charging station.
The electricity on the grid is in turn generated from a variety of sources; such as coal, hydroelectricity, nuclear and others. Power sources such as roof top photovoltaic solar cell panels, micro hydro or wind may also be used and are promoted because of concerns regarding global warming.
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| Charging station at Rio de Janeiro, Brazil. This station is run by Petrobras and uses solar energy. |
Level 1, 2, and 3 charging
Around 1998 the California Air Resources Board classified levels of charging power that have been codified in title 13 of the California Code of Regulations, the U.S. 1999 National Electrical Code section 625 and SAE International standards
.* or potentially 208V x 37A, out of the strict specification but within circuit breaker and connector/cable power limits. Alternatively, this voltage would impose a lower power rating of 6.7 kW at 32A.
More recently the term "Level 3" has also been used by the SAE J1772 Standard Committee for a possible future higher-power AC fast charging standard. To distinguish from Level 3 DC fast charging, this would-be standard is written as "Level 3 AC". SAE has not yet approved standards for either AC or DC Level 3 charging.
For comparison in Europe the IEC 61851-1 charging modes are used to classify charging equipment. The provisions of IEC 62196 charging modes for conductive charging of electric vehicles include Mode 1 (max. 16A / max. 250V a.c. or 480V three-phase), Mode 2 (max. 32A / max. 250V a.c. or 480V three-phase), Mode 3 (max. 250A / max. 690V a.c. or three-phase) and Mode 4 (max. 400A / max. 600V d.c.).
Connectors
Most electric cars have used conductive coupling to supply electricity for recharging after the California Air Resources Board settled on the SAE J1772-2001 standard as the charging interface for electric vehicles in California in June 2001.In Europe the ACEA has decided to use the Type 2 connector from the range of IEC_62196 plug types for conductive charging of electric vehicles in the European Union as the Type 1 connector (SAE J1772-2009) does not provide for three-phase charging.
Another approach is inductive charging using a non-conducting "paddle" inserted into a slot in the car. Delco Electronics developed the Magne Charge inductive charging system around 1998 for the General Motors EV1 and it was also used for the Chevrolet S-10 EV and Toyota RAV4 EV vehicles.
Regenerative Braking
Using regenerative braking, a feature which is present on many hybrid electric vehicles, approximately 20% of the energy usually lost in the brakes is recovered to recharge the batteries.
Charging Time
More electrical power to the car reduces charging time. Power is limited by the capacity of the grid connection, and, for level 1 and 2 charging, by the power rating of the car's on-board charger. A normal household outlet is between 1.5 kW (in the US, Canada, Japan, and other countries with 110 volt supply) to 3 kW (in countries with 230V supply). The main connection to a house may sustain 10, 15 or even 20 kW in addition to "normal" domestic loads - though it would be unwise to use all the apparent capability - and special wiring can be installed to use this. As examples of on-board chargers, the Nissan Leaf at launch has a 3.3 kW charger and the Tesla Roadster appears to accept 16.8 kW (240V at 70A) from the Tesla Home Connector. These power numbers are small compared to the effective power delivery rate of an average petrol pump, about 5,000 kW. Even if the electrical supply power can be increased, most batteries do not accept charge at greater than their charge rate ("1C"), because high charge rates have an adverse effect on the discharge capacities of batteries. Despite these power limitations, plugging in to even the least-powerful conventional home outlet provides more than 15 kilowatt-hours of energy overnight, sufficient to propel most electric cars more than 70 kilometres (43 mi) (see Energy efficiency above).
Faster Charging
Some types of batteries such as Lithium-titanate, LiFePO4 and even certain NiMH variants can be charged almost to their full capacity in 10–20 minutes. Fast charging requires very high currents often derived from a three-phase power supply. Careful charge management is required to prevent damage to the batteries through overcharging.
Most people do not usually require fast recharging because they have enough time, six to eight hours (depending on discharge level) during the work day or overnight at home to recharge. BEV drivers frequently prefer recharging at home, avoiding the inconvenience of visiting a public charging station.