and crimp on a regular spade terminal, and you can feed it off of regular terminals from the fusebox. However, it will be always on. You can get a relay as mentioned to run it off of the battery only when the car is on.
I have had very few problems using 45Ahr AGM (for SKS gen2) made by East Penn manufacturing- they sell under Deka, Napa (at least their AGM), Federated Auto parts, (I believe Duracell's AGM as well). I would suggest having a key off draw test done to see if you have something...