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Will a battery shut off switch reduce cranking amps

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Hello all:

I’m considering adding a heavy duty rotary battery shut off switch for safety, to my 48 New Yorker which has a 6v pos ground system, original wiring, a 6 volt pos alternator, and battery cables made from  0000 welding cable.  


My plan is to add the switch the positive ground cable then run wiring back to the cut off switch which I’d install in the passenger compartment for convenience.

My question is:  would I be  reducing the effectiveness (re: cranking amps) of my 0000 cable by installing the shut off switch using #10 or #8 wiring?  


Remember, the run will be from the battery pos ground terminal to the switch located inside the passenger compartment ….maybe  a run of 4+ feet of wiring.  (I don’t want the switch in the engine compartment because I don’t want to pop the hood each time I shut it down).

What grade wire would you recommend for this install to insure no reduction in cranking power?


Thank you.

David in Santa Cruz

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Yes. #10 or #8 might even catch on fire. Any of those switches reduce cranking effectiveness, as does more wire, more connections, etc. The starting current ALL flows through the ground cable, be it negative or positive.


If you are going to do it, use more cable the same size as your battery cables, and buy a big heavy top-quality switch, like might be used on a fire truck. @Matt Harwood might know a source for a switch. Some guys put the switch in the floor to simplify the wiring. Shorter is better. Good luck.

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