DC CHARGING

Driver Behaviour

There has been a discernible change in the charging habits of electric vehicle drivers with the advent of long-range electric cars. Charging at DC charging networks has dropped markedly while charging at home overnight has increased. Drivers prefers home charging. The bigger battery packs in the newer cars negate the need to find charging stations during the day. Drivers of commercial fleet cars behave in a similar manner.

 

Overnight charging is the preferred option of most commercial fleet managers because it may negate the need for expensive grid upgrades by utilising underused nighttime grid capacity and the overnight rate for power is generally cheaper than the daytime rate. The cost of daytime charging can be offset by the installation of Solar PV.

When to choose DC Charging

DC charging is normally provided where vehicles need to charge to 80% in 30 minutes or less

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Markets for DC Charging Stations

The market for DC charging consists of:

  • Intercity charging at freeway service stations
  • Destination charging in town centers
  • Depot charging for buses and commercial vehicles that require fast charging during the day
  • Overhead pentagraph charging at bus stops
  • Locations where a fast top-up may be required are apartment blocks, commercial developments, motor vehicle dealerships, taxi companies and places the vehicles exceed their maximum range during the day

Charging speeds at DC stations depend on the size of the battery pack in the vehicle, the rate at which the vehicle can draw power and the capacity of the charging station to deliver the power.

DC charging stations can deliver power at a rate of between 22 kW and 350 kW. Most electric vehicles on the road draw at less than 100 kW. A vehicle with a maximum draw of 80 kW will not utilise the full capacity of a DC charging station.

The Renault Zoe draws at the full 22 kW AC.

DC charging stations, particularly those rated to 150 kW can be expensive to install.

The cost/benefit is a trade off between the capital cost of the installation and the expected future revenues from power sales.

The current payback period is around 10 to 15 years however, this will reduce as the number of electric cars on the road increases.

DC Charging Power

DC charging stations can deliver power at a rate of between 22 kW and 350 kW. Most electric vehicles on the road draw at less than 100 kW. A vehicle with a maximum draw of 80 kW will not utilise the full capacity of a DC charging station.

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Choosing a DC Charging Station

Most DC charging stations provided by the different manufacturers have similar physical characteristics. However, the networking, load management, payment systems and power cabinet configurations offered by the various manufacturers can differ.

DC Charging Station Essential Features

A DC charging station should have at least the following features

  • Open Charge Point Protocol (OCPP) 1.6+ compatible. The station should be directly connectable to any OCPP compatible network management system. Some stations on the market can only be connected to the manufacturer’s network. OCPP connectivity is provided through a gateway on the manufacturer’s network. This is a security risk because the charging station provider has no control over the gateway side of the network and cannot install IOT intrusion detection devices on the manufacturer’s network.
  • Modular. Expandable from at least 50 kW to 350 kW or somewhere in between. Initial capital costs can be reduced by installing a 50 kW station and avoiding expensive grid upgrades. The station can be upgraded at a later stage when it becomes economically feasible.
  • Compatible with CHAdeMO and Combo CCS to facilitate both charging standards.
  • Max output voltage: CCS 2 920VDC, CHAdeMO 500VDC.
  • Max output current: CCS 2 350A, CHAdeMO 200A.
  • On-board load balancing so that two cars can be charged at the same time, one on CHAdeMO and one on CCS.
  • Facility to dial down the power output of the charging station
  • Power module failover. Remaining modules keep charging if one module fails.
  • Easy to install.
  • LCD screen for messaging and instructions. Should be daylight readable.
  • RFID card and Optional credit card reader.
  • ISO / IEC14443A
  • B MIFARE Classic
  • DESFire EV1
  • ISO 18092 / ECMA-340
  • NFC 13.56MHz
  • Rated to IP 65 and IK 10.
  • Total harmonic distortion < 5%
  • EMC Directive: Immunity Class A, Emissions Class A.
  • Cable length 5 meter or more.
  • Ethernet and on-board 4G modem.
  • Easy access via lockable front door.
  • Power unit either on-board or in a separate cabinet.
  • CE Compliant: Combo-2 (DIN 70121; ISO15118) IEC 61851-1; IEC 61851-23.
  • Max ambient operating temperature +50 Celsius.