advice on simple alternator excitation circuit?
here's my problem:
i have a 3 battery 160amp isolator under my hood such that my three batteries do not draw off each other (1 for car, 1 for amps, 1 for 'puter/etc)
the alternator has this wire coming off of it that reads the voltage of the battery and then decides how much voltage to spit out, called te exciter wire i suppose
it seems that when i connect a small wire from my main car battery to this wire, that battery becomes fully charged and causes the alternator to quit charging, but one of the other batteries may NOT be fully charged
so i suppose i need some circuit that will input 3 voltages, and output the lowest of those values out the other end... this sounds pretty simple, but the few EE classes i've had (and gotten c's in) arnt much help at this point (twas a while ago)
this will give that exciter wire the lowest voltage, and ensure all of my batteries are sufficiently charged
can anyone offer some design advice/insights?