Charging EVs

Another post that’s nothing to do with Wi-Fi.

CCS rapid connector (left) – Type 2 connector (right)
Photo – Paul Sladen

Zap-Map is a popular service in the UK for locating EV chargers and, hopefully, getting some indication as to their status. Recently I’ve noticed a lot of chargers marked as faulty with comments like “only charges at 10kW instead of 43kW” or “only supplying 7kW instead of 50kW”. These almost always mean the same thing – the user doesn’t know what they’re doing. The result is a charger gets flagged as faulty when there’s nothing wrong, everything is working just as it should.

I don’t think it’s entirely fair to blame the user here, yes they should have read the manual for their car, but this stuff can be complicated and the dealer supplying their car probably hasn’t explained this because they don’t understand it themselves (there are good car dealers out there selling EVs but I’ve yet to meet one).

In summary for those already bored, every time someone has reported a DC rapid charger is bad because it’s only delivering 7kW, they’ve just used the wrong connector, type2 instead of CCS most likely. If a charge point says it’s 22kW, you won’t get that unless you car’s onboard charger is capable to taking it (Read The Flippin’ Manual). When you connect your new car capable of CCS rapid charging at 100kW to a 125kW charger, you won’t actually get 100kW for much of the time and you might not see that high rate at all. All this is completely normal.

The first key point: public charge points are either AC or DC with many rapid chargers offering both. If you’re plugging in using a type 2 connector then you’ll be charging with AC. Most AC charge points require you to use your own cable but some, mostly older, rapid chargers have a tethered type 2 AC cable, sometimes labelled 43kW.

Fast Charging

The rate at which your car will charge on AC is dictated by the capability of the car’s onboard charger and how much power the charge point signals the car can take.

AC charge points are not chargers at all, they’re basically a fancy switch that supplies mains power to the charger built into the car so it’s important to know what type of onboard charger your car has. It’s most likely to be 7kW (single phase), 11kW (three phase), or 22kW (three phase) if it’s a Renault Zoe or some models of Tesla.

Note: Three phase chargers require a three phase cable. There have been instances where dealers have provided the wrong cable for cars that have a three phase charger as an option. If your 11kW capable car is plugged into a 22kW charge point but only charges at 7kW, check the cable is correct.

Charge points themselves are either single phase in which case they can supply about 7kW or three phase and able to supply up to 22kW, occasionally as much as 43kW, and you can use any of these with any car.

For example my Kia has a 7kW onboard charger. If I connect it to a 7kW PodPoint at the local Lidl I’ll get about 7kW (usually 6.6kW). If I connect it to the 43kW AC connector of a BP Pulse Rapid charger I’ll get about 7kW. So what do I get from a 22kW point? Yep, I’ll get 7kW. If I connect my Zoe with it’s 22kW capability into the same 43kW rapid, I’ll expect to get 22kW.

Rapid charging

eVolt rapid charger with AC, CCS and CHAdeMO

Rapid chargers really are chargers and supply DC directly to the battery in your car, with the charge rate controlled by the car’s battery management system (BMS). These use a different type of connector, either CCS (most new cars) or CHAdeMO (Nissan Leaf, old model Kia Soul EV) and these cables are always tethered, permanently connected to the charger. Earlier I mentioned that some rapid chargers have an AC cable, this can cause confusion as, of course, it will fit your CCS car…. but you’re then using AC and not DC, which is where most of the errant Zap-Map complains come from.

The vast majority of rapid chargers are nominally rated at 50kW with 125, 150 and even 350kW chargers being installed.

Just as with AC, how fast your car actually charges depends on the capabilities of the rapid charger and the car. The big difference is that many cars limit the charge rate depending on the battery’s state of charge and, sometimes, the temperature so how fast it can go will vary.

To give an example again, my Kia can charge at up to 77kW over CCS. In practice it can only take this much power when the battery is below 40% and the charge rate soon tails off. Fastned have really good information about this for many cars. Their graph shows that although my car can take up to 77kW it steps down a few times, and once the battery is over 75% it drops to below 40kW, then below 30kW before tailing off to a trickle as the car approaches 100%

This is why you should never take your car to 100% on a rapid charger… it takes ages and ties up the charger, stopping others from using it. Typically charging on a rapid is also more expensive, so you’re wasting time as well as money…. and annoying anyone else waiting.

I typically see about 43kW reported by my car, which climbs to up towards 50kW right before it sharply steps down at just over 75%, exactly in line with the Fastned graph.

What these graphs demonstrate is there’s a tactic to time efficient rapid charging. If you’re making a long journey, plan charging stops when the battery is going to be getting low. Charging from 20-60% is generally faster than going from 40-80%.

There are folks who say all this is too complicated, and maybe it is. Most EV owners will just plug in at home and never worry about it, but it’s worth understanding at least some of this so you don’t make a fool of yourself on Zap-Map comments. It isn’t that many years ago we had different types of petrol and two stroke oil to contend with, not to mention distributor points and the fact a car would never start on a damp morning. By comparison knowing a couple of headline numbers is hardly a major barrier to EV adoption.

What I’ve said above is true of most cars. There are, of course, exceptions. Firstly Tesla have their own charging network which in some cases delivers rapid charging over type2 connectors. I have no experience of Tesla’s chargers. Some early models of Renault Zoe with the quick charge option can AC charge at 43kW. I believe they’re the only car that can do this and even Renault dropped it. Whilst all models of Renault Zoe can charge at up to 22kW AC only the very latest cars have CCS capability and even then it was an option until mid 2021 so there are plenty of Zoes around that cannot DC rapid charge. There’s no risk of confusion with this as the CCS plug won’t fit.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.