I think the thing only requires regulated voltage, not internal or external and it maintains the starting battery
independent of the house bank. I have no starting battery I just use the extended house bank as my engines are very small. You can download a pdf installation
and operation manual from balmar's web site, I read it and decided that I didn't need it.
$50.00 and including shipping
is a little shy, makes the cost of the used regulator that I installed too pricey.