Jérôme Faissat 9th May 2018 1 Min Read
Another question about charging time that comes back a lot. Whether you have a Tesla, a Porsche, a Volvo or a BMW, the answer is “it depends”! So here we go a simple widget with a simple answer!
In the UK, the most common type of home charging station is 7kw. Read “it outputs 7kw of power”. This is because most of the UK residential homes are supplied with a single-phase supply whereas in Central and Northern Europe 3 phase supply is much more common. 3 phase supply would mean that you could charge up to 22kw (that is 3 times faster!).
Another factor to take into account is the amperage. In our example, we’ve assumed 32 amp. so with the supply type, you can say “single phase at 32 amp”. That’s it. If you say this, people would assume you know what you’re talking about. Amperage can be limited by different factors: your current electrical installation, how many devices/appliances running in your home, etc…. So before you get your home charging station installed, a survey may highlight that your charging station can only draw at 16 amp (otherwise it will be unsafe).
Hybrid cars which have a small battery tends to have a limited charging capacity. It means that even if you have a powerful 7kw charging station, you won’t be able to charge at 7kw. You’ll be charging at half the speed (3kw) because of the limitation of your car.
Batteries behaviours also affect the charging time. Especially with fast charging, you may have noticed that the first 50%-80% charge quicker than the remaining 50%-20%. This is because Li-ion battery charging follows a profile designed to ensure safety and long life without compromising performance called “recharge circuitry programming”. To cut a long story short: the battery will demand a current that is adapted to its current charge status to avoid damaging the battery.
Any electrical circuit has inefficiencies. Heat and distance contribute to this inefficiency meaning that even if your charging stations should output 7.2-7.4kw in theory, it will actually generate slightly less than that in reality.
Jérôme is the boss of Andersen’s day-to-day managerial and service delivery. With extensive experience of retail system development and property and financial services, Jerome has an eye for quality and control. When he’s not mapping the future, he loves to talk to customers, drink French wine or speak Mandarin. He even finds time to walk his two dogs in the evenings.