EV charging capacity vs. charging speed – which is more important?

Gavin Braithwaite-Smith 8 NOVEMBER 2021

The next generation of electric cars will boast some seriously impressive charging speeds. The Audi E-tron’s 150kW charging capacity and Porsche Taycan’s 225kW figure are the stepping stones to our 350kW future.

However, charging capacity is only half the story: electric car owners should pay as much attention to charging speed.

As Audi points out, most EV charging occurs at home or work – places where the time factor does not play a significant role. Speed is far more important when charging on the move, via a fast or rapid charger.

Audi goes on to say that many customers look at the charging capacity as a key attribute of an electric car, but ‘this value is of only limited use if it concerns quick refuelling of range at a fast charging terminal’. What’s more important is a higher charging capacity over a longer period of time.

In other words, if an electric car charges with maximum output over a short period and lowers its power early, the charging speed is also lowered. This is where the so-called ‘charging curve’ comes in.

The curve of a High Power Charging (HPC) terminal with 150kW output stands out at a high level thanks to its continuity. In most circumstances, the Audi charges between five percent and 70 percent states at the maximum capacity before the battery management reduces the charge.

In other cars, the battery management system reduces the output before the 70 percent state of charge, which increases the overall length of time needed to recharge. An Audi E-tron 55 will hit 80 percent capacity after 30 minutes.

Fully charging from five to 100 percent takes around 45 minutes. The final 20 percent is always slower to preserve the life of the battery.

If you intend to recharge on the move, knowledge of your car’s charging speed could add up to a few hours saved over the course of a year.