Battery switch question

So a question for the group about battery switches...

The previous owner on my 34 LRC said he never touched the battery switch located in the salon, and in fact had left it on "both" the entire time he owned the boat (10 years) even when at dock on shore power. What if any problems does this create? Does it add to electrolysis with the engines being "hot" all the time? Is there anything else I'm missing here?

On ALL my previous boats I always used the three way battery switch to turn off the batteries to the engines when I was not operating them.

Thanks in advance for all of your opinions and suggestions.

Well, working from your last comment upwards, the battery switch generally serves more than just the engine. It usually supplies power to all of the DC house loads as well- lights, etc

There is no problem keeping the battery switch on all while at the dock. I do it all of the time. It makes sure that both house and starting batteries (typically the 1 and 2 batteries or visa versa) are both charging all of the time.

The only time I switch is after I drop the hook and shut down the engine. Then I turn the switch to the house battery bank so that I don't run down the starting battery. Then in the morning when I am ready to go, I briefly turn the switch to the starting battery and after the engine starts turn it back to all so that both banks are recharged by the engine alternator.

David

If it's the typical set up then being on "both" just means the banks were paralleled together into one big bank. Not a problem as long as you dont run the bank down while off shore power. Then you have killed your start bank. More modern installs would replace the 1/2/all switch with a voltage sensing relay so you dont have to mess with or remember a switch.

Thanks for the info. FYI...I have a house bank, engine bank, and separate genset battery.

When on the boat the switch is on house. Unattended off. Both to parallel battery start or to charge start battery. Start battery has no charger.