2.4. Configurations: fast AC, rapid DC or a mix?

When planning your electric vehicle charging infrastructure, it is important to consider the anticipated consumer pool and their likely charging patterns. The type of charging infrastructure may also be constrained by the location, be it from a spatial or power availability point of view.

Fast alternating current charging (AC)

Attributes of this approach are:

• Public fast AC charging most closely resembles the home charging experience of those who own driveways and can be referred to as destination charging.
• This may suit those whose vehicles have plenty of downtime on a given day as it means that they can leave their vehicle for longer periods.
• The probability is that only two to three drivers will charge their vehicle from each socket on any given day, with one or two daytime slots and one night-time slot.
• As they have smart charging capabilities, these devices can enable access to discounted and low carbon tariffs where in effect.
• There are numerous examples across Scotland of fast AC chargepoints being installed on-street and in car parks.

Rapid direct current charging (DC)

Attributes of this approach are:

• Rapid DC charging, often referred to as journey charging, requires the driver to stay close to their vehicle during its charging period, as the faster charge time allows a higher throughput of charging sessions. Allotted charging time may also be more limited due to overstay charges.
• Allowing more vehicles to recharge on a unit per day creates a benefit, but accessing the quicker charge offered can create a convenience cost to some drivers for whom it requires a dedicated journey and wait-time.
• At the ultra-rapid level (>100kW), wait-time comes close to resembling the ICE car refueling experience, with recharging possible in as little as 15 minutes.
• Frequent rapid charging is believed to lead to a quicker degradation of an electric vehicle’s battery state of health.
• It is much more common to find rapid chargers in car parks than on-street, in part because their footprint is larger, which makes their installation only possible on particularly wide streets.

A mix of fast AC and rapid DC

Attributes of this approach are:

• In off-street charging hubs, it is common to find a mix of AC and DC units to serve different user types. The blend of these will depend both on local needs and power availability.