IEEE Electrification Magazine - December 2013 - 48

Electric
Utility
Power
System
Service Drop
EV Energy Transfer System

Building
Service
Equipment

Meter

dc Charge
Port
ac Charge
Port

Branch Circuit

Meter
Grid

EVSE

EV
Power Electronics and
Motor Controller
Electric Drive
Motor

Transformer
OBC
Battery Pack with Battery
Managing System
ac Electrical Energy

dc Electrical Energy

Figure 1. A diagram of an EV energy transfer system (modified from Young et al.).

Level 3 fast charging extends the charging power to a
much higher level (excess of 50 kW). consequently, the
charging time is significantly reduced. the level 3 charging
stations are expected to charge a peV battery pack to 80%
Soc in fewer than 30 min. one of the frontier eV manufacturers, tesla Motors inc., is aimed at fully charging its eVs in
5 min in the foreseeable future using its supercharging
stations. to implement level 3 fast charging, an off-board
charger is necessary to convert three-phase 208 V-600-Vac
power to 200 V-450-Vdc power, which fits the voltage range
of the battery pack. however, level 3 charging comes with
extremely high costs, which include the installation, infrastructure, and maintenance costs. it should be noted that
the rapid charging of a battery pack can cause it to overheat
and potentially decrease the battery life. Moreover, drawing
ultrahigh power from the grid increases the demand from
the grid and might cause an overload of the local distribution facilities. consequently, level 3 charging is mainly
intended for commercial and public charging stations.
table 2 lists the charging characteristics and infrastructures of some of the commercially available peVs on the

market as of December 2013. all listed peVs are equipped
with oBcs compatible with level 1 and level 2 charging. all
peVs, except for the tesla Model S, use a universal charge
connector, which is defined by the standard Sae J1772.

battery charging Strategies
a Li-ion cell has a higher energy density than other battery chemistries such as lead acid cell, nickel cadmium
cell, and ni-metal hydride cell. in peVs, the energy density and the weight of the battery are two of the most critical parameters that determine the electric range of the
vehicle. consequently, the Li-ion cell has dominated the
market of commercially available peVs. this can be
observed in table 2, as all the listed peVs are equipped
with an Li-ion battery pack. although extended life cycles,
increased energy density, and a slight cost reduction have
been achieved with the evolution of battery technology,
the Li-ion battery pack is still the most expensive and
heaviest component of a peV.
it is not only the battery chemistry that determines the
power level at which a cell can accept a charge but also

TAbLe 1. charging power levels.
Charging
Level

Power Supply

Level 1

120-Vac
single phase

1.92

US$500-800

1.4

3-4

~17 h

~7 h

Level 2

240-Vac
single phase

19.2

US$3,150-5,100

3.3 (onboard)

8-10

~7 h

~3 h

6.6 (onboard)

17-20

~3.5 h

~1.4 h

Three-phase
208-600
Vac or dc

240

>50
(off-board)

50-60

30-45
min

~10
min

Level 3

Power Limit
(kW)

Installation and
EVSE Cost

US$30,000-
16,000

I E E E E l e c t r i f i c ati o n M agaz ine / december 2013

Typical Charging
Power (kW)

Range for 1 h of
Charge (mi)

Charging Time
EV

PHEV

Table of Contents for the Digital Edition of IEEE Electrification Magazine - December 2013