That's a great idea until I can get to putting in a new staror this Winter. Then I wouldn't have to give up precious riding time this Summer.Just to be clear I'm not endorsing any particular brand or size but these new lithium jump batterys are light and should be able to easily recharge the bikes battery multiple times.
Using one of these wired to the battery would help the bike start then if left on should continue to charge the battery until it is charged while you ride.
You could strap it to the seat....
By the way ya'll I installed the last new crank shaft seal in my bike about 2 months ago.
Are you sure that this charger works when not plugged into a 120 AC wall outlet?
I looked pretty good at the specs, and don't see that it charges a battery if not plugged into an outlet. I might just be missing something?