My 83 Blazer has two batteries, one primary and one spare. The spare or auxillary battery is just keeping charged by the battery isolater with nothing running off it. My battery light came on full and I checked my primary battery when I got home. It read ten volts. I charged it up that night and the next morning I start the truck to warm it up. The battery light is still full on, and after the truck gets warmed up, I come out to start looking for what's wrong and I see bubbling liquid coming out of the auxillary battery at the vent on the end closest to the pos. terminal. Now that's wierd. I didn't think there was even liquid in those batteries. But clearly something is seriously wrong. I'm going to go out there right now and do some alternator and charging systems testing right now. Any ideas?