If that is the case I would get a diode type auto switching Isolator. The reason being it will maintain your batteries, it will cycle usage between the two and keep them both charged. This is an advantage because if needed it will also draw off of both batteries to start your car... The problem with the manual switching (solonoid type) is every now and then I have seen people who forgot to switch their batteries over to charge the auxiliary and end up with a weak battery when they need it. (use to go to Moab alot)
The diode isolators do not allow you to use both batteries to start the car. The same diode that allows a charge into the battery keeps the isolated battery from being used to start the car and keeps the main battery from draining with the isolated accesories.
speaking of cold weather, the wife and i road triped to dallas over the last 3 days and now i know what cold weather is. its been as low as 23 degrees. we took the prius and man the cold kills its gas milage. we droped from geting 41mpg doing 80mph to 32 mpg doing 80 when the temps droped in to the 30s. its two hundred sumtin volt bat seems to be holding up just fine in the cold.
Sorry probably phrased that bad it should have read Isolator/combiners they do utilize both batteries to start the vehicle when needed. http://www.hellroaring.com/battery1.php
If you want dual batteries, run a couple of 6V batteries and connect them pos to neg, like on a bass boat. You'll have basically one huge 12V battery that lasts for a LONG time. There were a few racers around here that ran that setup for a while. Best of my knowledge, it worked great. Personally I've never once had a single problem running a single Optima, but then again I don't sit in the vehicle for hours on end listening to the radio either. Several years ago in my old car, I had a decent radio system in it, and it would run about 2 hours until the battery ran down to where it wouldn't start the car. Even then, I could tell that it was getting low by the lights in the radio-they would dim and sound quality was dropping.
Yes, but on heavy equipment (over the road) they use solenoids to run the batteries in series (24v) to start the engine and then it goes back to 12v to charge and run the accesories (parallel). Some of the earth moving equipment is all 24v and the use two DDD batteries - about 240 amp hours.
