Posted by Gordon on Monday, March 22, 2004 at 5:21AM :
In Reply to: Automatic Low Voltage battery cut-off switch? posted by EdC on Sunday, March 21, 2004 at 9:24PM :
A couple of points worth mentioning.
I've not found an automatic 'anything' that really works on these systems, except for the Accumate which I use yo keep all my vehicle batteries up. they are cheap enough to buy more than one, and I tend to wire the spare socket that comes with them to any vehicle I finish so all I have to do is plug it in.
Isolator switches do work, never seen an automatic one worth having though. It is possible to have a double battery setup with a diode on one so only one will discharge to flat and still eave the other fully charged to re-start the engine.
The problem with isolator switches is voltage drop. I reckon you lose 0.5 to 0.75 volts for most 6 and 12 volt systems. A 12 volt system in good order will take a 0.75 volt drop and start the engine no problem, but a 6v system with an isolator switch in it will drop the voltage to 5.5 or lower, and on some of these systems that means the difference between starting and not starting. I found this out on a 6v GMC system, but it would apply to Dodges too.
Accumate to charge up and keep it charged up, that's the thing. I've got about a years use on two of them with no serious problems, and they are switchable between 6 and 12 volts.