electric vehicle charging stations for sale:What is fast charging?
This is the first part of a series exploring fast charging technology. In part 2 I discuss car batteries and the variables that influence charge speed. In part 3 I discuss how fast the next generation of EVs will be charged. In this part I'll explain what fast charging is. In part 3 I explain how fast the next generation of EVs will be charged. In part 4 I discuss the relationship between station capacity and economies of scale.
How fast charging differs from 'regular' charging
Fastned is rolling out a network of fast charging stations. But what exactly is fast charging? This is the first blog on fast charging and the exciting developments we expect in the next few years. But let’s start with the basics: what is fast charging? And how is it different from ‘regular’ charging?
All batteries - including those in electric vehicles - use Direct Current (DC) for charging and discharging. But the electricity grid delivers Alternating Current (AC). Therefore AC from the grid needs to be converted to DC so it can be used to charge the battery. This is done by an AC/DC converter.
This AC/DC converter is part of what we call a charger. Chargers can either be integrated into the car as an onboard charger, or chargers can be external to the car e.g. a fast charger. Today, virtually all electric vehicles have a small onboard charger. You can use a cable to connect the onboard charger to a regular AC socket in your garage or plug it into a charge pole. The charge pole delivers the AC required for the onboard charger to charge your battery. So a charge pole is not actually a charger but an intelligent socket to plug-in your charge cable.
If you want to charge faster, the AC/DC converter and hence the charger need to be bigger. But a bigger charger is heavier, takes up more space in the car and ads complexity and cost to the car. So car manufacturers usually choose a relatively small - and therefore slow - onboard charger to optimise between these factors.
Fast charging is different
An external charger that does the AC/DC conversion is a lot bigger, heavier (around 400 kg) , more complex and more expensive than an onboard charger. But it is also a LOT faster. That is why they are usually referred to as ‘DC fast chargers’ or just ‘fast chargers’. A typical fast charger that is available today delivers 50 kW which charges about 5 to 15 times faster than an onboard charger. (The next generation of ultra fast chargers is expected in 2017 and will deliver 150 kW and might be upgraded later to 350 kW. This means you can charge your battery 15 to 100 times as quick in comparison to using the onboard charger. I’ll cover the subject of ultra fast charging in a future blog.)
Most - but not all - electric vehicles have a second inlet to plug in the fast charger cable. The fast charger cable is fixed to the fast charger since it needs to handle the high currents of fast charging. The inlet used for fast charging is wired directly to the battery so it completely bypasses the onboard charger.
Since the actual charger is located outside of the vehicle, the onboard electronics of the car (the ‘Battery Management System’ or BMS) and the fast charger communicate with each other. The BMS determines the charge speeds based on various parameters, and the fast charger adjusts the charge speed accordingly.
Exception: Renault Zoe
For the Renault ZOE drivers reading this blog: yes, your car is an exception. It has a large onboard charger that can charge at up to 43 kW with the Quick Charge option. However, it is not capable of DC fast charging as described above. Other car manufacturers - for reasons described earlier - choose DC technology for faster charging.
The next blog in this series will be about car batteries and charge speed.
Roland van der Put is the CTO of Fastned and heads the Network Operations Center. He graduated as computer science engineer at the Delft University of Technology and has a background in computers. His interest in electric cars was triggered after installing his own solar panels and driving a plug-in hybrid.