AC/DC aren’t just one of the greatest rock bands of all time – they also take their name from the two most common types of power transmission.
Alternating current (AC) and direct current (DC) are different ways of transmitting power to different devices. Up until now there has been no need for the average person to know the difference; however, with the introduction of electric vehicles, it is now helpful to understand the difference.
Some quick physics
Thinking back to your high school physics class, you might remember that electricity can flow either as direct current (DC), meaning it’s continuously flowing in the same direction, or alternating current (AC), meaning that it flips back and forwards.
The power that comes into our homes in the UK is generally AC – this is because AC is generally a more efficient way of transmitting eletricity over long distances.
However, many devices need DC to work properly.
For example, the battery in your electric car can only be charged up using DC electricity.
AC charging
When you plug your electric car into the mains power supply at your house, the electrical circuits inside your car have to convert the AC electricity (from the National Grid) into the DC electricity that your car needs to charge its batteries. Most modern electric cars have no problem doing this, however there is a limit on the amount of power they can convert. For some electric vehicles this limit is as low as 7 kW.
Most home chargers are of this type, and perfectly fast enough for charging up overnight – indeed, we are leading installers of home electric car chargers in Glasgow.
However, if you want to charge your electric car faster, you need to charge it up using DC power.
DC charging
When you use a DC charger, the charger itself converts the power from AC to DC, before sending it down the cable to your car. Because the charger doesn’t have to rely on the electrical circuits in your car to convert the power from AC to DC, the power output can be far higher.
DC chargers can have very high power outputs. For example, Gridserve operates DC chargers with a power output of 360 kW – about 50 times higher than the average home charger!
So, if you are in a hurry, so-called DC “fast chargers” are the way to go!
The only downside of these is that they can be few and far between in the UK – because the power supply from the National Grid to these super fast chargers also has to be “beefed up,” and they are very expensive to install. Nonetheless, fast DC chargers are becoming more common in service stations and petrol station forecourts across the country. For example, bp pulse has a significant number of 150 kW chargers at Harthill services on the M8 between Glasgow and Edinburgh in both directions.
While charging at home is a convenient way to meet your day-to-day charging needs, we look forward to seeing more DC chargers coming on line in the near future, for those times when your battery needs a quick top-up on a longer journey.
