When source voltave raises above 13.2 volts, relay accuates allowing sec. battery (represented by cap) to charge. Once source volt drops below 12.8, relay releases, and led represents drain on secondary cell(while source remains isolated). Purpose for maintaining lvl of secondary batt; allowing secondary circuits to deplete its pwr source without depleting primary batteries, a.k.a. the one that starts my car... PLEASE CRITIQUE, trying to bld a minimal and reliable circuit.
