Page 24 - Issue 3 2023

TECHNICAL

Converting all ten million vehicles in
South Africa to battery operation would
result in an additional grid load of 70 GW
in an uncontrolled environment.

Types of charger
There are several methods available
for the charging of electric vehicles.
The vehicles are usually equipped with
a variety of charging sockets to allow
connection of each type of charger.
Charging may be done by means of an AC
supply to an internal charger, limited to Figure 6: Solar PV charge station (Paired power)
22K kW for a 3-phase supply, or from an
external DC supply. Smart charging units Rapid charging rates vary according to the charger type but can be in excess of 200 kW.
which can communicate with the vehicle’s Rapid chargers are becoming more powerful and the exact charging rate depends on a
user and the smart grid or home/office particular vehicle’s charging capacity and the type of connector used. Every EPM will have
energy management system are available. a controlled charging rate in order to protect the battery.

Home charging - low power plug-in Solar charger
This is essentially a trickle charge Solar charging stations are available and range from single car units using ten panels and
unit, rated typically at 3 kW, which is providing 5 kW of charging capacity, while providing covered parking for the vehicle,
incorporated in the EV charge circuit. The to multiple car stations using 16 to 20 panels. Charge units could incorporate a storage
unit is plugged into a normal domestic battery.
electric socket. Characterised by a long
charge time, this is sometimes referred to Vehicle to grid (VTG) and Vehicle to X (VTX) (bidirectional) charger
as an emergency charge unit. An external With VTG technology, energy stored in the battery can be fed back through the charger
DC charger can also be used in plug-in to provide power to the supply point. This electricity could be fed to the grid, to the
mode. home, or to the building where the vehicle is parked. The system requires a smart
bidirectional charger, and the vehicle needs to be equipped with a V2G compatible
Home charging wall unit battery management system. Several manufacturers are offering models with this option.
Home charging wall units are permanently This system finds application where vehicles are left parked for long periods of the day,
installed single phase AC chargers with such as residences, offices and factories, and the vehicle owner can specify when the
a typical capacity of 7 kW. They leave vehicle will next be required when connecting to the system, ensuring a full charge when
sufficient power to run the household on leaving the premises.
a single-phase feed. A 20 kWh battery Vehicle-to-home would be particularly useful in the South African evening load
would require three to four hours for shedding situation, where a 20 kWh battery could provide power to the average home
a full charge. A top-up charge of 5 kW for more than four hours. This would require disconnection from the grid during power
should take less than an hour. DC external outages.
charging versions are also available.
Higher charge rates require a 3-phase EV adoption
supply and could be realised by kerbside The high purchase price of an electric vehicle is a barrier to most people, even though the
chargers or charge stations. running costs are a fraction of those of ICE vehicles, while offering better performance.
The cost of an EPM puts it out of reach for the average motorist. The motor industry
Rapid charge DC has been accused of focusing on the luxury car market for EPMs, when what is needed
These units bypass the internal charger is a cheap reliable form of transport. This was confirmed recently by the CEO of a major
and provide DC directly to the battery at a manufacturer who said that the company had no intention of producing cheaper EPMs.
high current level. Rapid charging stations Government policy also supports the all-electric vehicle, whereas ICE hybrids and plug-in
are usually installed at EV charging hybrids seem to be more suitable to enable the transition from full ICE vehicles to EPMs.
stations, and have charging capacities of
up to 170 kW, claiming 100 km of charge References available on request
in ten minutes. The unit consists of a high-
power AC/DC converter and controller. Send your comments to rogerl@nowmedia.co.za

24 | energize Issue 3 | 2023 SUBSCRIBE FREE