Correct dual battery usage?

[capercanuck]

I have a 25 foot Sunray Cruiser with one 350 mercruiser, one alternator and two batteries. I also have one of those 1-both-2-off battery switches. I have been boating for the past few years and have always used the batteries on a turn system. If I go out today, I use #1. If I go out tomorrow, I use #2. I use them in turns. I'm beginning to wonder if this is correct. Should I use one for stricktly starting, and the other for running electronics and such, once underway? The battery switch isolates the alternator, I think, so that the alternator doesn't blow when I switch batteries while running. Also, considering that I am running a 350 mercruiser, what type of batteries should I use? I think one is has high cranking amps and the other is deep cycle, but I plan on changing them this season, and if I had numbers when purchasing that would help out alot. The batteries were in it when I purchased it a few years ago and I'm not sure if they were the proper ones to begin with. Any information is always appreciated!

 

[Spidybot]

Re: Correct dual battery usage?

Different philosophies calls for different setups. If you have one battery designed for starting and one for ongoing consumption you'd use it differently than two starting batteries.<br /><br />If the dual setup is meant to ensure starting power at all times I'd keep both connected while running, switching to one while shutting motor off. Even if your equipment should drain the battery completely you'd always have the second ready for starting - and the get the charge up for the whole setup. (PS! A flat battery needs careful charge by a suitable charger to get completely up again - running the motor alone wont do).<br /><br />Depending on your budget an automatic battery switch/manager would take care of it all.

 

[Ralph 123]

Re: Correct dual battery usage?

You should consider buying a battery combiner like the West Marine Combiner 150. It allows both of your batteries to be charged when the alternator is charging but isolates the batteries when they are being discharged. This prevent you from draining both batteries by accident. <br /><br />I would use a deep cycle for my house battery (everything but engine) and a marine Starting battery for the engine. <br /><br />When regular batteries are drained below a certain point they become "damaged" and are never again able to hold a full rated charged. Deep cycle batteries are designed to be able to withstand being nearly fully drained w/o dmage. So while your camping, power is only being drained from your deep cycle "house" battery and you don't have to worry about starting the egine or damaging the batteries.<br /><br />I have twins and use 3 batteries. 2 dedicated starting batteries and 1 house battery for everything else, along with 2 combiners and 4 simple on/off switches. Fool proof.

 

[capercanuck]

Re: Correct dual battery usage?

Thanks for the info!