yeah but id be only really worried if you had a illegal bicycle,
If you did attract that attention, They find no bomb or anything bad, Be expected to be strip searched and if you have anything that is illegal like a ebike that's putting out more watts than the legal limit, they will try bust you for that, But I guess if you are just charging and not riding, they cant even bust you.
I think if you don't look like some kind of common terrorist, you should be okay in public places...
I remember the days when I had 6 gauge power leads running off my backpack to my controller, It looked suss, But people these days are more accepting and they know its probably a ebike setup
You might get some older folk worried.. not sure..
Just make it as stealth as possible so people don't look at you and make you feel uncomfortable