I have this...

http://www.amazon.com/dp/B010DP8PIU/

Unfortunately the only time I've used it was when the power went out in my house for charging mobile devices and using the flashlight.

It held a full charge through winter though and based on my research it was suitable for my car.

The overhead light I mean the light on the ceiling of your car that turns on when you open the door. I turned it on to look for something in my car while it was parked. Since it turns on when the door is open I forgot to turn it off when getting out of my car. And my window tint made it hard to notice it was on when I got out. Did it like 3-4 times in a couple months.

Ultimately I'd like some type of high charge portable battery that has a power outlet so I could plug in battery chargers and radios and all.

The website says it has a 20Ah reserve. So something like this would probably be better, but having the availability to use a jump start, air compressor, and various outlets is nice for what I bought.

edit: This thing is pretty dumb.

Ankers pack is pretty cool.

Something like this is more useful to me since I ride a motorcycle.