Thread: Master power switch. Electrical GURUS needed

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Your idea should work just fine,except instead of the fuse I would use an automotive circuit breaker,sooner or later your gonna forget about having the switch turned off and will pop the fuse. The circuit breaker will reset itself in a matter minutes. G.M.used them for power seats and wiper motors for years. Any Auto Parts store should have them in stock.

Great idea! So do you feel the ground "keep alive" would trip a breaker, or blow a fuse, if a short occurred, or if the starter was cranked (without the switch turned on) as well as the positive wired set up would?

For some reason I keep thinking that a smaller gauge ground wire (keep alive), even fused with a low amp fuse/breaker, would still allow enough of a ground to crank the engine, or allow a short to occur, where as the positive cable would not. I don't know why this is stuck in my head. Am I totally wrong about this concern? I think I am, just want confirmation from someone who knows more than me about 12v electrical systems..

What of my concerns re the alternator/regulator, if one switched off while the engine was running?

I read one comment on another forum that said, "regardless of the switch wiring at the switch, (- or +), the engine would not stop running unless the alternator exciter wire was also disconnected"..I don't know what to think of that..but I seem to recall that a vehicle can continue to run, with battery disconnected. Perhaps this is where I heard of the alternator/regulator issues occurring. If that is the case how is the master switch a benefit at a race track. Car hits the wall, throttle stuck wide open, driver unconscious, track Marshall turns off the master switch, engine keeps screaming..I don't get it? I suppose the fuel pump would be switched off, so that would be a plus, as well as other electrics, that might short and cause a fire..

I suppose in an emergency, where the driver is still aware, you would turn off the ignition switch, then turn off the master switch..

My opinion is to not to try to reinvent the wheel on this one. There is a reason every boat that uses a master battery switch is wired on the positive side, with the switch as close to the battery as possible. That reason is you want to be able to disconnect any potential spark source in case a wire comes loose or touches ground. If you do it on the negative side you still have a long run of positive cable just laying there waiting to touch metal and become a dead short.

Now, I know we are talking about a car vs a boat, but same principle applies. If you want something like memory to stay hot all the time, simply connect that accessory in on the positive side of your disconnect side. Everything beyond that is protected when the battery switch is turned off.

Don