Dual batteries

[John Hofstetter <hofs@domain.elided>]

>No, but they didn't give a ton o details.  They were comparing to diode-
>based isolators, and other kinds of switches.
>
>Ken "who was daydreaming of a battery switch on my dash today" Farmer

Ken,
FWIW, In the past, I have preferred the marine type rotating switches 
that are about 6" in diameter and by rotating the switch, you get a 
choice of battery one, battery two, both batteries, or no batteries. I've 
used these on Travelalls where I had plenty of mounting room. They last 
forever as long as they don't sustain major physical damage. I've seen 
people use a much smaller switch with a lever to operate it that switches 
between the batteries and can also disconnect them. I really have no 
knowledge about these. 

The slickest electrically operated system I've seen was dual Ford type 
starter solenoids that were switched from inside to offer the same four 
options as the marine switch, but all done from two switches inside the 
cab. A person could also use a DPDT switch to offer any three of the four 
options all from one switch. 

A digester or two, in the past has expressed concern over the Ford 
solenoids being used to supply continuous power, but I've never seen this 
problem in dealing with maybe thousands of vehicles that had Ford 
solenoids. I just don't think they have problems with the contact staying 
shut for long periods of time. Solenoids usually fail from arcing as the 
contacts open and close. Admittedly, the concern expressed was over the 
electromagnet windings being able to stay continuously energized, but 
those of us who use Ford solenoids in our Scouts don't encounter this 
problem. Basically, as I think about it, I'm using a Ford solenoid in my 
Scout, with one battery, to do exactly what I'm describing in the dual 
battery setup and it has worked this way for many years. 

Thinking on my butt (at my chair) as opposed to on my feet, you could 
have one of the solenoids activated by the key and so when the key was 
on, there would always be power to start the vehicle (for any 
mechanically impaired people who might be driving the car), and if I'm 
thinking correctly, the only around the solenoid hot wire would be the 
ignition switch, and the only directly key operated device would be the 
solenoid. All other normally-key-operated devices would derive their 
power from the activated solenoid. Actually, to repeat myself, this is 
pretty much the way my Scout is wired. 

Thinking more about this I've not accounted for accessory-position 
operated devices, but rather than use more digest space, I'll put that 
issue on the back burner (which doesn't get too hot anymore).

John H.