12vDC Isolator

[MarkT]

I am trying to build a unit that will charge two batteries without allowing one to be discharged by the other. I want the accessories in my vehicle to run off a "new" auxiliary battery. What I don't what is the "new" battery to discharge the "start" battery for the engine. Can anyone help?

 

[john monks]

Normally a second battery is powered through a diode that runs directly from the alternator. And a diode is added between the alternator and the main battery to prevent back current from occurring. This works if you have a voltage regulator that is separate from the alternator. RV dealers sell these types of things. Check this:
http://www.ehow.com/how-does_5005295_battery-isolator-work_.html
or this:
https://www.google.com/#q=battery+i...08,d.cGE&fp=72ee8731386af3c6&biw=1280&bih=830