Dwn4BassAlan

I heard that too, about life span. Mostly I heard people say that you needed an isolator between them to avoid charging/depleting issues. But I'm thinking it's not worth the hassle to keep the stock in there and just tossing one of the 1200's in the front and back, and doing 2 runs of 1/0 ofc between the batts.

if it were me id ditch the stock bat unless it is a big one. lower resting voltage on lead acid stock battery will act as a continous load on the agm xs power whenever your car is off. i was told as long as you daily drive it or at least every 3 days drive it, you should be fine. i used to run 1 of each, my buddy runs 1 of each no prioblem. if you go on vacation or dont drive for a while disconnect them from one another

as long as its not a wet cell you should be fine, if its a wet cell then it will slowly discharge the agm batteries, had a buddy who just had to replace his agm and stock cause of that.