safety and care with leisure batteries?

[Paul C]

Just to confuse things (slightly), many boats' battery bank negatives aren't connected together - because the domestic bank has a shunt in between the battery's negative terminal and everything else which wants to be connected to negative. (In fact on our boat there's enough fat negative connections to justify a bus bar for them).

 

I guess all the cables and terminal insulators (you have terminal insulators, right?) are the same colour - anyone with common sense would wire a boat with black negative cables and red positive ones. I don't think thick cable (like, 50mm2 and above size) is commonly available in anything except these colours.

 

But at the end of the day, and as a general rule for all vehicles, the only 100% sure way to know which terminal is which is to closely inspect the battery and search for the + and - signs next to the relevant terminals. And if someone says you can be sure by eg tracing cables to a starter or earth, certain older cars were wired up as positive earth.......

[nicknorman]

Just to confuse things (slightly), many boats' battery bank negatives aren't connected together - because the domestic bank has a shunt in between the battery's negative terminal and everything else which wants to be connected to negative.

 

...or you could say that when a shunt is fitted, the battery negative terminals are still effectively connected together, just via a slightly thinner bit of wire which will drop up to 75 millivolts under high current conditions. Conditions where in a different installation without a shunt, the negative interconnect might anyway drop 75mV if it is a bit undersized.