Sears with 1SaleADay has the Stanley 40 Amp Automatic Battery Charger w/ LCD Display for $50 with free shipping. Claims to start most cars in one minute.
^ This is a modernized old-school bench top battery charger, not a portable jump-starter, I mean it can do that but it has no battery in it AFAICT.
No need to plug into a wall outlet periodically since there is no internal battery to keep topped off, except of course it has to be wall outlet powered when you need to charge the (car, etc) host battery with it.
these have to be plugged into an outlet and topped off once a month, more if you use it.
also, the battery in these last for a few years, just like any other battery.
^ This is a modernized old-school bench top battery charger, not a portable jump-starter, I mean it can do that but it has no battery in it AFAICT.
No need to plug into a wall outlet periodically since there is no internal battery to keep topped off, except of course it has to be wall outlet powered when you need to charge the (car, etc) host battery with it.