Battery cut-off switch

[SouthernDragon]

I've bought a used boat that had for 20 years the cut-off batteries switch isolating the ground (negative) batt cables.
Shouldn´t be on the positive cables ?
What´s the problem if I leave it as is ? (If worked for 20 years.....

)
Thanks in advance for your replies

 

[Ross]

Normally you break the positive. But that seems to be tradition. Positive and negative were established rather arbitrally way back when they assigned electrons a negative charge and protrons a positive charge, never the less we are stuck with tradition.

 

[RAD]

Without really thinking about it the one reason would be for saftey.......you know its the negative being broke in the circuit but a mechanic working on the boat doesn't and also the engine is not grounded when that switch is off but again I haven't thought about the effects

 

[kloudie1]

May have had roots in the UK .. Years ago, many cars built in the UK had the positive side of the battery grounded ??

 

[Bill Roosa]

Couple of thoughts:
It does not matter from an electrical standpoint if you make the break in the main positive or main ground cable. The electrons cannot complete the path from battery terminal to battery terminal so you are not any (or just as) safer one way over the other.
The actual physics is electrons are pushed out of the negative terminal and flow "backward" down the ground through the load and then return to the battery positive terminal. What this tells me is when I have a positive cable disconnect the entire "ground side" from the switch to negative terminal has lots of electrons on it trying to find a way to the positive terminal or any other way off the boat. (think of the + being 0 volts and the - being negative 12 volts and it makes more sense). This could have corrosion issues but since I have forgotten most of my collage chemistry I can't seem to recall how that would effect the "anode" and 'cathode" relationship. The electrons do all the damage not the positive "holes" that normal current is thought to exist of.
I'd agree with Ross that having it "backward" may cause some confusion when the maintenance man comes to call.