Changing battery switch positions

[FreeZone]

Anne and I are new Catalina owners and we are still trying to figure all the systems out.  I know you are not suppose to change the battery switch while the engine is running and the alternator is charging.  But, after starting the engine and before you excite the alternator, would it be ok to change the battery switch?

Joe and Anne Johnson

[Tom P, IMPULSE #233, '86]

Joe and Anne,

Welcome to Catalina ownership...It really is a great boat, and the people at this site are really great as well...

Assuming you are speaking about the main battery switch which selects battery "off", "1", "all", or "2"...

It is my understanding that this switch is a "make before break" switch, so switching between battery "1", "all", and "2" while the engine is running is fine; "make before break" means that it connects to the new setting before it disconnects from the old setting, so the alternator is always connected to at least one battery during the switching process...

The only time you can fry the alternator is by putting this switch in the "off" position while the engine is running...

I'm not sure what you meant by "exciting the alternator" in your post...I believe this is an automatic function which occurs as soon as the alternator pulley starts spinning, and is not controled by an external switch...

I regularly switch my battery position switch while the engine is running to bring both banks up to a full charge (if they are low) and have never damaged an alternator...However, you must be sure to stay away from the "off" setting...

Hope this helps...
Tom P

[Stu Jackson]

Joe & Anne

Why would you want to change the position of the switch to begin with?

If you have a starting battery and a house bank and start the engine with the starting battery, unless you have a combiner, only the start battery gets charged from the alternator.  So why not do what Ron Hill suggested and start with "all" to charge both?  Or start the engine with the house bank, charge that up while motoring, since the start battery can be used in the case your house bank is flat?  

The amount of amp hours drawn when using the start battery is so small that it almost never needs to be recharged.  If your house bank is large enough for your uses, you should always have enough power to use it to start the engine, and so have the start battery as a backup.

I recommend that you buy Nigel Calder's Boatowners Manual.  There is an incredible amount of information there, and it's up to you, not just the switch, as to how you want to set up your electrical system.

Stu