fengshui said:
... I've just been driving over there just before bed when low, leaving the Spark charging there overnight and riding my bike back home.
Have you considered that a "free" public site probably didn't envision you camping out at their spot, blocking it from anybody else?
If the site is not placarded with CVC-22511 language, which allows towing for vehicles not charging, it probably should be. This camping concept is becoming a bigger and bigger issue with freeloaders looking for a way to save a few pennies on charging. It affects everybody else in the EV community, unfortunately.
The Mitsubishi headquarters had a Chevy Volt driver who camped out at their J1772 spots. What did they finally do, after repeatedly asking this person NOT to camp their? They blocked ALL the chargers for ANYBODY, including the CHAdeMO DC charger that Volts and Sparks can't even use.
I doubt this will dissuade you from continuing camping / freeloading, but knowing that you're using Rabobank (which generally all have 70 amp service for Tesla, with units owned by Tesla) helps us isolate your case, and find a corrective action.
The easy answer is to return the units to proprietary Tesla plugs so that you can't use it at all. But, that's not really the point of public charging, either. So, I might recommend a timer on the car that only allows 2 hour charges, and times out, forcing the camper to retrieve the car that isn't charging, or get towed in accordance with CVC-22511.
Or, placarded for no overnight charging at all, and just tow every car left overnight. Don't worry, we'll fix it for the benefit of all.