Blog & News
April 17, 2018

EV Charging 101 – Charging and the Input Power of EV’s

Electric cars & charging

Electric vehicle drivers don’t have to be professional electricians, but understanding the basics of electricity will make everything easier. In this blog post, we’ll tell you the basics of charging speed. Other than the charging device, the charging speed is affected by the size of the fuse and the EV model.

Single-Phase Electric Power or Three-Phase Electric Power?

Normal, "slow" charging devices supply EV's with three-phase alternating current (AC). The standard power socket at your home provides single-phase power. In a way, this means that a charging device triples the capacity of a standard power socket.

The maximum power supply of Virta’s charging devices is 22 kW. For the electrical capacity of a residential building, this is quite a lot. With Virta’s smart admin panel, you can limit the charging power to a level that suits the property: if the ampacity of a building is for example 16A, the maximum power of the charging device can be set at 11 kW.

Alternating Current (AC) or Direct Current (DC)?

The battery of an EV has to be charged with direct current (DC), but a regular charging device supplies the EV with alternating current (AC). This means that the current has to be transformed from AC to DC, which happens in the EV’s built-in charger.

In practice, the electricity flows from the charging device or power socket into the EV's own charger. In the built-in charger, the electricity is transformed into a form that suits the battery, and then the power is fed into the battery at a set maximum wattage, which varies depending on the EV model. Fast charging devices feed the car battery directly with DC. As this makes the built-in charger in the EV redundant, it allows faster charging.


Table: Examples of EV input power and an estimate of range per hour.


In a nutshell:

The built-in charger of an EV affects how quickly the vehicle is charged. A powerful charging device doesn’t necessarily charge the EV faster, if vehicle’s built-in charger is set at a lower input power. A fast charging device provides the EV directly with DC, making the charging process faster. 

Before you purchase a charging service, it is important to examine at least what the electrical capacity of the property is, as well as the input power of your EV’s on-board charging. The charging power and battery size differs a lot from one EV to another, and both the power and size of the batteries are constantly growing with new EV models that are being developed. This means that it is wise to build a charging system that in residential buildings supplies at least 11kW (3x16A), and in commercial buildings 22kW (3x32A), in order to be ready for the growing demand for effective charging.


If you want to know more about EV's, make sure to read more on our blog. Don't hesitate to contact us if you have questions. 


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