There was some thread on here about 3 years ago--I do not recall what it was. I pointed out that when I was a boy in the '50s-'60s, my friends and I would snatch several gulps of water from a garden hose that was outside someone's house when it was hot outside. We did not trash their yards; we just walked up the walkway, turned on the spigot, slurped, turned off the spigot, and walked back to the street. A couple of people claimed that this was theft, and posited that we had a sense of entitlement. Sorta hard to measure the amount of theft--in those days water was around 1.5 - 2 cents per 100ft^3, so clearly the "theft" was less than a mill.
Yeah, I get it. One person does this and the next you know, everybody and his cousin are doing it. Charging cables are everywhere. It is now a hazard to walk near all those electric vehicles while the crowd gathers round to point and deride and shame all those freeloaders. The local news will show up. "PEOPLE STEALING ELECTRICITY FROM MALL!!! STORY AT ELEVEN!"
Like a lot of things in our lives, common sense, moderation, courtesy, consideration, and reasonableness should prevail. Leave your phone number with a note explaining what and why. Make a concerted (but not crazy) effort to secure permission or at least notify someone like security of your intention.
Perhaps the best solution would be to approach the management of the center to install a couple of L2 chargers near those 120V plugs. Ya never know!