Originally Posted by Stu Jackson
The repeated comments about not using the battery
switch when the engine
is running are meaningless UNLESS you know how it is wired. If the alternator
output (AO) goes to the C post of the battery
switch, then it is prudent to not move the switch. If the AO goes to the house bank, you can turn the damned switch off when the engine
is running and there will be no harm because the AO is connected to a battery.
Sure, you need to know how it is wired. However:
, and everything else on the boat except the bilge pump
, is wired to my Blue Seas 1-Both-2-Off switch. For 17 years and 6,500 engine hours, I've been switching batteries with the engine running with no problem.
Since it is "make before break", as is just about any reasonably modern battery switch, you can switch between 1, Both, and 2 without offending the alternator diodes - so long as you don't go through Off.
Some switches, such as this one
are designed such that this is easy to do without accidentally going through Off.
Others, such as this one
make it riskier, as it's relatively easy to flip all the way to Off when you're intending to go from 2 or All to 1.