2 batteries in a prius

If the 250A breaker keeps breaking, then obviously the PAC200 is NOT ok. Just don't forget the big ground from the amp to the battery(s), otherwise that will smoke. And by the dc-dc converter being the alternator, I merely meant from the 12V POV. But there aren't any signal wires, merely the 12V wires across the 12V battery (which may be up to 14.4V when charging) - hence how a voltage sensing "smart isolator" could work. (But I suggest a non-voltage sensing method - unless the voltages and delays are appropriate.)   

so how would u suggest doing the big 3? im confused as to what u mean about the wire over the 12v.... there are several wires. also my moms boyfriend was being nosy and read some of what u said and he told me he thinks u want me to get a starter solenoid lke this http://#/ws/eBayISAPI.dll?ViewItem&item=360346511450&viewitem=#ht_2681wt_1165 http://www.go2marine .com/product.do? no=86818F&WT.mc_id =gb1&utm_source= googlebase&utm_medium =productfeed&utm_campaign= googleshopping he said thats the only continuous solenoid......i dont kno anythign abotu it....i have been lookign for isolators like the pac200 or noco or things like that..... im getting confused with everyone saying different things..... wouild u mind just sending me a link as to which isolator or w.e that i need? i dont remember if i wrote back early today or not but i found where im going to out the second battery. it will fit about 3 feet away from the main battery and less then a foot away from the amp. which is all underneath the sub. i have to do a few mods to make this all work but its the only way the everything will fit. its porlly going to take me a few weeks between work and a few other projects i got going on. so that gives me time to figure out the isolator situation.

Just make sure the power cables (+ve & -ve/GND) to the amp from the battery/s handle the amp load.

using 0 gauge so will b fine