Run your second alt off your driveshaft, under the car, then have an extra deep cycle optima battery in the rear, like the trunk or if this is your van, the rear cargo or even mounted under the floor with an access panal to get to it, just make shure it is encased, wire in a simple fuse block/ relay block into an assesable place, wire your fans into that battery fuse box, yes the battery wouldn't charge when stopped but, the deep cycle battery will hold good, until the light turns green. Of course, couldn't it be a relay not hooked up right and drawing too many amps?