batteries

[Guest]

I currently have a deep cycle battery serving all my purposes on my motor boat. I want to add an auto battery for cranking purposes only and use the deep cycle for electrical/electronic purposes. How do I wire the batteries? In parallel? Through a switch?

 

[Guest]

You should wire the engine to the new starting battery. Then connect the positive terminal of the deep cycle battery through a high current on/off switch, to the starting battery positive.

Whenever the engine is running, or if you want them in parallel for starting, turn the switch on. Remember to turn it off whenever you turn the engine off so the house loads don't discharge the starting battery too.

There are various more complex circuits you could use but this is the most basic. Avoid any circuits that put a switch between the engine and the starting battery because if you switch it off while the engine is running you stand a good chance of damaging the alternator.

If you purchase a battery combiner, or equivalent, it will do the switching automatically for you. You can read about them at http://www.yandina.com/combInfo.htm and there are owner's manuals you can download that have a number of more sophisticated circuits.

Avoid installing a battery isolator. This item would require modification of the alternator wiring on your engine and they have a voltage drop so your batteries would no longer get a full charge.