[Richbot]

One of the reasons lead acid batteries are sized the way they are is to provide longevity in situations like you described. A li-ion battery behaves differently so it can be sized (when i say sized i mean cca and ah, not physical size) accordingly.

I have to ise a trickle charger with a brand new OEM battery in the car it still won't hold a good enough charge for more than a week. Sure it is good enough after sitting for weeks to start the car and run things, but not good enough to rule out a low voltage freakout from the various electronics, which is annoying and trickle chargers are easy. No way I would run any kind of downsized battery without a trickle charger for times when it's parked more than a couple days. It'll be a few years before I need another battery but when I do maybe I will have a moment of what the hell and buy one of these. It's only money

Just be careful the FAA doesn't ground you...