Standing still at 500km/h...

Since batteries store kwh, there’s an easy way to compare charger speeds. Plugged into a 100kw DC fast charger, an EV that uses 20kwh/100km is getting 500km of driving range per hour. Connected to a 7kw AC home wallbox, the same EV is gaining only 35km per hour.

Unfortunately, it’s not quite this simple. An EV’S charge rate isn’t determined only by charger output. The EV’S hardware is the limiting factor.

All EVS come with a charge port that’s connected to an on-board battery charger. This controls the conversion of AC grid power to DC current for storage in the battery. The industry standard plug is the Type 2 or Mennekes.

This is what you’ll find at one end of the emergency charging cable that comes with any new EV, allowing charging from a normal power point at around 7 to 15km of range per hour. The Type 2 is also found on home wallbox and public AC charger cables, good for 15 to 100km/h.

Actual charging speeds will depend on the rating of the EV’S battery charger. Connect a 22kw AC charge point into a car with a 7kw on-board charger and it’ll only take the lower power.

Most EVS – the Renault Zoe ZE is an exception – are also equipped with a plug for DC fast charging. There are two types capable of handling the high energy they deliver. CHADEMO is a Japanese developed plug standard, while CCS Combined (so called because it includes both a pair of DC fastcharge terminals and a Type 2 plug) is Europe’s solution. In this VHS versus Betamax-like battle, CCS Combined appears the likely winner, partly because Tesla has joined the consortium working on its development.

Most new DC fast chargers have two attached cables, one with a CHADEMO plug and another with a CCS Combined plug. As with AC charging, the maximum DC fast-charge rate is determined by the vehicle’s hardware, not the charging station.

Frequent DC fast charging hastens the rate of EV battery degeneration, speeding degradation of cell chemicals and causing internal corrosion. This means EVS aren’t suitable for drivers often doing big daily distances. For average drivers, who might want to DC fast charge once or twice a month, it’s not a major problem.