The problem with the OP's case is that he appears never to have attached the charging cable. As the sign says--" recharging point only"
I've attached the Webb V Wandsworth (2210311085) case which he won even though he had finished charging.See also 2240125760.
So, if attachment of a cable becomes the tipping point, the OP is in difficulty.
However, does the signage say anything about attachment or indeed the need to move on once the battery is recharged? Does it say anything about a time limited bay? The PCN certainly indicates "during restricted hours"--are we to presume that relates to " during the permitted hours" The TMO states:-
(d) Electric vehicle charging place may be used for the leaving during the permitted hours of such electric vehicles for so long as necessary to allow that vehicle to be restored to full charge by connecting to a recharging point.
What the hell are the permitted or restricted hours?
This is a clear failure to comply with the Regulation 18 duty of LATOR 1996 because a very significant part of the information as to the effect of the Parking Places Order has not been conveyed to road users by the sign in situ.
To emphasise this ground I would reference Harvey Kutner v London Borough of Camden 2230471029.
"There has been a history of High Court and Court of Appeal decisions concerning signs conveying parking restrictions and a traffic authority’s duty under Regulation 18 of LATOR. These establish that a failure to comply with the Regulation 18 duty as to signage is a proper ground on which an adjudicator may allow an appeal against the issue of a PCN, on the ground that the alleged contravention of the relevant Traffic Regulation Order did not occur. The key Court of Appeal case is Herron v. The Parking Adjudicator and Ors [2011] EWCA Civ 905, and R (London Borough of Camden) v. The Parking Adjudicator [2011] EWHC 295 (Admin), per Burnett J. at [50] – [51] is also instructive".
Forget about the SYL, go for their failure to prove the parking contravention through the signage in place.
Mike