This post is written mostly based on my experience of the issues with my Renault Zoe rapid charging.
While I am not an EV mechanic I am however technically minded which helped in my diagnosis.
A few people seem to also be getting this issue on their Zoe when other Zoes are not hence this detailed post about what you can do to help check to see if there is an issue with your car or the chargeposts.
Overview & Why it's not always earth.
When charging the Renault Zoe can present itself with a "Battery Charging Impossible" error on the dashboard, this can mean many things but the most common thing that people think it is the Earthing to blame.
It is correct to believe the Zoe is fussier wth earthing standards compared to other models of EV and this is likely because in a case of failure the Zoe has 43KW going into it vs most at 7KW.
However the earthing still has to be really bad for this to be the issue with even for T T Earthing systems a target in most installations being less than 100 Ohms which should be fine for the Zoe (The exact value aren't perfectly clear).
Furthermore the Zoe is much more common of a car on UK roads now, from my research originally because it wasn't a common car these earth faults were common. But now when installing chargers most will account in the Zoes, along with this the other fault of incorrect RCDs being chosen is also solved because of the increased popularity of Zoes.
Finally if an operator doesn't believe their charger is suitable for Zoes there have been some pictures of stickers being put on chargers where the manufactuer believes the earth is too high.
Now I repeat, it can be the earth in some cases, however for the reasons above I don't believe it is as common now as 4 years ago.
But they're French!
Another point is that they're French! In my case the three brands of rapid chargers that failed were all designed in France, they're not going to design a charger which doesn't work with the most popular EV in France, which is also made in France!
Furthermore the Renault Zoe is the main car capable of being able to handle 43KW AC Charging, the manufacturers aren't going to put this connector on and it not be designed to be within Renault's Specifications.
In fact the DBT Units (Primarily Ecotricity) are designed for Renault ZE Standards, along with some other chargers also mentioning they follow Renault ZE Standards.
How to check if it is the earth
It's quite simple to check if it is the earth, while it is still plugged in, you'll need the CanZE App and a compatible OBD Dongle. Plug the OBD Dongle into the socket (located under a cover where the lighter socket is) and launch the Can ZE app.
Setup CanZE to use the OBD dongle then in the app, either swipe left twice or click the three dots in the top right corner to switch to the experimental menu (Indicated by a folder and flask in the top left) then click BCB.
You can see on this screenshot that the ground resistance measured 24 Ohms, a perfect value.
I also suspect it would log a DTC of an earthing issue but as I haven't experienced a charger with an earth issue I can't confirm this part.
From what I have researched if it is an earth issue it'll attempt to charge then fail and not re-try automatically but I also can't confirm this part yet.
So can it be the earth in some cases? Sure, however this is usually down to poor installation standards or an older installation. As mentioned operators know the popularity of the Renault Zoe with it being one of the most popular EVs in the UK and they're not going to install chargers that they don't work with. It doesn't make business sense to keep having customers complain and then an engineer keep going to the charger to test it.
However for the reasons mentioned above, it's likely not the earth. To be sure ideally have an OBD Dongle in your car with the CanZE app on your phone to be able to check.
Interested in EV Chat?
I'm setting up an UK EV Owners Group channel on discord at https://discord.gg/rkqCgG2 , with the goal to be where you can chat instantly with other owners.