Why do you need our IKXS4 battery isolator?

Because it provides automatic separation and connection of the starting battery in parallel with a secondary battery according to the voltage level of the starting battery. This isolator will constantly scan the starting battery voltage for connection and charging of the secondary battery to the starting battery. An example of where this would be beneficial is if you are connecting an AGM battery alongside a battery comprised of Lithium Iron Phosphate. AGM batteries tend to rest between 12.8 and 13.0v, whicle LFP batteries tend to rest between 13.2v and 13.5v.