The so-called "trickle charge" will work fine, as long as the wiring is in excellent condition, and rated for the load the car draws. I don't know the specs for French wiring, so I can't be more specific. Essentially, if you treat the wiring as if it will be powering a medium-sized, continuously operating electric space heater outdoors, you will be ok.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.