Battery switch saga continues

[capz]

It's been a much debated topic on this board about battery switch positions when anchored/running/starting. I've read from many of you guys that moving the switch with the engine running will damage the alternator.

This excerpt is in the Q&A column "Ask Chuck" in Boat U.S. magazine, Sept. 07, summarized.

Question
"I hear different opinions on whether I should run my boat on Batt1 or Batt2 going out and switching to the other returning. Others say run with the switch set to all...."

Answer
"The primary reason for having two batteries an a sector switch is to ensure you will always have a battery charged to start the engine. A good way to assure this is to start the engine on 1 battery...........Once the engine is running switch to the "both" position to recharge both batteries".......

I stopped switching over to both when running but here's another opinion, from someone who seems to know his stuff, saying it's ok to do just that. :huh:

 

[skolbe]

That is an accurate statement - you just don't want to turn the batteries off. Many people don't want to risk accidentally turning them off or if something goes bad - they break there alternator.

 

[Dave S]

Whether it's a good idea to switch batteries to BOTH while the engine is running is certainly debatable but I prefer not to try it and risk creating a problem.

The way we boat, and with only a single engine, we will probably never run one of our batteries down enough to fully discharge it. So if we can, we start the engine with the battery we were using while on the hook. That way, only the battery that was being used will get the full benefit of being charged by the engine's alternator. But if it won't restart on that battery, then we can switch to the other one and start the engine. The alternator is not meant to bring your battery up to full charge anyway once it has been run all the way down. The only way to fully recharge a battery it is to hook it to shore power and let your battery charger bring each battery up to their full charge.

 

[mrtopknight]

Better yet, you could just not worry about it and carry a portable jump kit onboard. :thumbsup:

 

[estebanj]

I exchanged an email with Chuck based on the article. I was commenting how it's OK to change 1/2/BOTH with engine running, but never go through OFF, which he agreed.

He re-emphasized that it's OK to go from 1/2/BOTH b/c batteries switches work on a "make before break" principle, so when switching 1/2/BOTH, there is always contact with the alternator.

Like Dave, I never switch with the engine running just for peace of mind, but the theory says it's OK... just don't go through OFF.

Esteban

 

[Sorrento 25]

Or just install a Blue Sea dual circuit setup with a combiner and never give it another thought.