BERLIN: As electric cars start to cover ever longer distances on single charges, the phenomenon of "range anxiety" - the fear of being stranded somewhere with an empty battery - is slowly fading away.
But even with electric vehicles that cover longer distances you can still find yourself waiting for the battery to recharge before you can continue your journey.
How long do I need to charge up so I can make it home? You might find yourself wondering this at a charging station. As sophisticated as many electric cars are, they often don't offer a simple answer.
Electric cars charge at different speeds, and to get a sense of how fast a car will recharge, there's one metric that it helps to understand: the average charging performance.
The problem is that manufacturers typically only state the maximum charging power or the time for a full charge. However, this often makes it impossible to see how many kilometres you'll be able to cover by taking a one-hour break at a charging point.
To get a number you can use to work out how far a certain charging time gets you, you need the average charging power. The rule of thumb for this is to simply subtract one third from the maximum charging power.
This is because while the maximum charging power is almost reached when the battery is empty, it drops and only reaches a fraction when the battery is at 80%. This is due to the charging management, which is supposed to protect the battery.
What does this mean in practice?
Say your electric car charges at 180 kilowatts (kW). We subtract a third to get the effective average charging power, in this case: 120 kW.
To work out your range per hour of charging, you then need to divide this hourly charging power by the amount of power your car consumes per hour.
This means that if your electric car consumes 20 kilowatt hours (kWh) per 100km, it should recharge for a range of 600km in one hour.
