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Something you’ve always wanted to know about fast charging
Dec 17, 2018

What is fast charging? And why is a network of fast charging stations so important for the breakthrough of electric cars? we will offer an introduction to answer these questions

What is fast charging

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 electric 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 vehicle as an onboard charger, or chargers can be external to the vehicle (for example 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 point. The charge point delivers the AC required for the onboard charger to charge your battery. So a charge point 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 adds complexity and cost to the vehicle. On top of that any component in a vehicle needs to be automotve grade to ensure its reliable operation for the lifetime of the vehicle. So vehicle 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 can be a lot bigger, heavier, 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 very common fast charger delivers 50 kW which charges a vehicle about 5 to 15 times faster than an onboard charger. The next generation of fast chargers was introduced in early 2018 and delivers 175 kW and can even be upgraded later to 350 kW. More on the impact of this later.