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All of the battery kill switches I have seen are for 12 volt systems with a negative ground. Is it a problem to use this type of switch on a 1941 110 coupe 6 volt system with a positive ground. Any specific recommendations would be appreciated

Wayne Cain

Most remote battery kill switches are just a continuously rated relay, some wiring, an inline fuse and a small toggle switch.

If you find a 6v normally off relay that is continuously rated at or above your starter relay amps, then that would work just as well. The wiring is fairly simple.

Good Morning...The really old school approach is to open the distributor and remove the rotor and put it in your pocket. In the Army, in Heidelberg, in 1969, a friend of mind was picked up by the Military Police and when they found the rotor for a military Jeep, in his pocket, they thought he was a thief...until he took them to the Jeep assigned to him! Ernie in Arizona

Ernie, that would help to keep the car from being started and driven away but will do nothing to eliminate battery drain that sometimes happens when our old cars sit for a while. A battery disconnect or removing the cable is the only way to stop that!

For old cars usually the only thing that can even draw power when the car is off is the cig liter, and the clock. Of course some cars there are a couple other things, like torsion level. That being said, all of these except the clock should not draw any power because they switch themselves off automatically, and most people's clocks don't even work. A nonfunctional clock should not draw power since a clock only draws power when it winds itself.

If you suspect phantom drain on the battery the best thing to do is hook up a milliammeter with everything in the car off. Depending on various factors, the natural rate of self-discharge from the battery could have a fast enough effect that it seems like there is phantom drain.

Quote:

Not quite true as the points in a clock have been known to fuse together and I know because I’ve had it happen. I’ve also had the BAT relay points burn together in the voltage regulator which causes a draw.

Waynecain; there are ‘disconnect switches’ intended for this purpose that have threaded binding posts. What you need is a cable that has the specific polarity SAE terminal for the battery end, and then a terminal for the switch . . . likely a ring end. Follow that up with a second cable to go from the switch, again likely a ring end terminal, and then to the specific location on the engine where the original cable attached. That second cable will likely have a ring end at both ends. You’ll need to do some digging for a disconnect switch suitable for the current associated with a 6 volt system. Avoid any product that doesn’t state both the surge and continuous current capability of the switch. As a rule of thumb, modern cars of a few years back used 4 gauge battery cables, and I believe the 6 volt systems used something more like 1 gauge. A 1 gauge cable has twice the area (1/2 of the resistance per foot) of a 4 gauge cable. Typically the mounting bracketry will be locally fabricated.

I happen to disconnect the positive side on my Packard, but the decision of which cable to disconnect is up to you. My switch is purely mechanical, meaning it is activated by my hand, not a remote electrical switch, although after getting into the car ready to go, and then finding out I had not closed the cut-off switch is a bit frustrating. I have another 6 volt application that instead of a disconnect switch I remove the positive battery cable.

dp

Polarity doesn't matter with a manual switch. Current rating does. A cheap switch is no good. My car has a manual switch in the floor board on the driver side. It can be reached from the driver's seat. It does not add any length to the battery cable, and it works very well. It disconnects everything, including any accessories.
Older Caterpillar dozers (D-7, 1973) had a manual battery disconnect switch I bought a new one about 5 years ago. I don't recall what it cost, but it's a very heavy duty unit, designed for use in a 24 volt system for a 760 CID diesel engine.

switches are more rated on amperage than voltage. However, lots of junk coming from offshore, caveat emptor. Much like wire size, there has to sufficient contact area for current to pass without heating. It not just at shutoff, but how it works when turned on. Voltage only affects the insulation, per se. Compare to hydraulic flow. Current is the volume(area dependent), Voltage is the pressure(containment dependent).
It's typical in 12VDC- to put the switch on the neg as it prevents sparking when reconnected. I'm not sure either is appropriate for + ground. I haven't studied that one. Make sure the instructions specify and not just the same as 12. Could be shocking experience.
I tend to use AMG so they aren't as predisposed to drain cycling failure. I can forget to disconnect the switch, too. Charge it before I use.
Positive grounds will leak off continually as it also plays an anodic protection role, preventing corrosion. Negative ground only passes through the body when flow required. It's one of the inherent issues with 6VDC +, the other is it requires twice the amperage/larger wires/contactors which drains wet cells faster. The old generators/VRs were only 30-35A rated, so if you didn't run it long enough, the battery never gets fully charged. Typical 12s today are 45-60A or more.
Those charge/discharge wheatstone bridge ammeters don't tell you much about battery condition. Just the difference in technical understanding of the times.
If you want original you have to put up with original.

Packard offered a battery charger outfit
for urban winter commuters. An undersize generator pulley was also available for taxi, police, and other adverse condition service.
Battery rental, charging services, and service trucks with exchange/rental batteries used to be common. Batteries are better today, and vehicles have much more robust and better regulated charging systems. Automated cold start systems prevent inept operators from running down their batteries and wearing out their starters.

Battery charging aside, it's always a good idea to drive a car for half an hour or more, or ten miles or more, any time it is started. More is better, especially in colder weather. The benefits are many.