Batteries blowing up, not from my install. I strongly suggest using some sort of isolater or a battery relay. Some people don't But most in the sport do when it comes to the main car battery. Why kill the main car battery? Now if you running multi batteries for the sound system and have more then one alt its not neccesary. But thats a diffrent story. And yes I have put two alt on a teg. If you can not afford to go out and by two new batteries then I strongly suggest you Isolate the two batteries. same brand, group size,cca sould be used if there is no isolater. I had a customer bring me his car that he did and used to diffrent batteries. I was tuneing his car and there was a bammmm. the over charged battery exploded. scared the shyt out of me. Now these batteries were under the hood. Imagine the mess in back of a teg in the trunk. or a custom trunk.