INFINITUM Desulfator installation on a Peugeot 308 - YouTube
You have to remove the air intake to get at it.
If you look further down that thread you can see a lump of metal coming out from under the LH flap (RH pic of two), going behind the air filter. What's that about if not the neg connection?
Strike that; the video finally loaded. What a crock of ..... the French have cooked up. How to make something as simple as a battery far too complex for the layman to deal with! (Jobs for the boys? Yup!)
It is really easy when you know how though, possibly easier than skinned knuckles and strange contortions of your hands and arms to reach through the gap on a 'normal' car.
This sort of thing is all part of the charm of French electrics though - much like why my passenger side front window is disconnected (it opens itself when it feels like it and then wont shut!).
Wasn't sad to see the back of it. I wouldn't buy another Renault. In fact probably any continental european car for that matter...... Not that that's even an option now.
My battery is in the boot, very easy to get to with no faffing..