Re: Electronics and Electric Battery hookup
Heres my 2-cents on battery configuration. It does differ from the other recommendation. My comments on dual-purpose batteries are at the bottom.<br /><br />A battery bank can be anything from a single battery to 8 or 10 or more batteries. They are commonly referred to as either a starting bank used primarily for starting applications, or a house bank used primarily for all other nonessential electrical needs on a vessel. It is very common for smaller vessels to have a single battery stating bank and a single or double battery house bank. Some boats may have 3 banks where that third bank has enough batteries to supply appropriate current to 24v applications, like a trolling motor. The third bank is a luxury.<br /><br />You can think of your starting bank as the necessities of life and the house bank as the luxuries of life. Anything and everything that you absolutely need should go on the starting battery. This would include the ability to start your engine, your VHF radio (think safety), the instrument panel lights, and your navigation lights. This battery bank should be receiving enough charging current from the alternator while underway to support all of this low-amp stuff. At anchor, with engine off, none of this stuff is used (it's switched off) except the VHF and it doesnt draw enough current to be an issue (1-amp/hour?). There is disagreement as to whether or not the anchor light should be supplied by the starting bank. I consider that single 25-watt bulb part of my navigation lights and have it configured to a starting bank that is sized appropriately.<br /><br />The luxuries you can (but probably prefer not to) live without are your (heaven forbid!) fishfinder, trolling motor (its looking bad), GPS (because you are smart enough to carry paper charts, too!), the RADAR, the stereo (its looking worse!), your electric beer cooler and/or margarita blender (why continue living?), etc. None of these things are required to ensure your safety and should not be allowed to interfere with your ability to start your engine(s).<br /><br />Configured this way, you can go off into the sunset, trolling until you kill your house bank beyond resuscitation, and still get home safely. At any given time there is between none and a very minimum load on your starting bank
actual engine starting excepted, of course. If you were to take you boat to any experienced, reputable boatyard that does marine elecrical and drop it off without any electrical wiring, your boat would come back with the wiring configured as described above. That anchor light may be wired to either bank
you should decide what works best for you.<br /><br />I am not a fan of dual-purpose batteries except where a small vessel has a single battery that is used infrequently to support both the necessities and the luxuries. A dual-purpose battery is a deep cycle battery with inappropriately thin lead plates. This allows more surface area contact with the electrolyte, which results in more amps flying out of that critter for starting applications. It is not optimized for either deep cycling or starting and as such, any use means there is more internal chemical reaction (corrosion) than if using a battery that is application specific. It is the odd child out but it does have its niche, albeit a small niche.<br /><br />If you consider AGM batteries, while not technically dual-purpose, they function well in either deep cycle or high-amp starting applications. They are a deep cycle battery with extremely low internal resistance. This allows them to spit out the high amps needed for starters. The newer generation of AGMs is a deep cycle battery that will outperform a traditional flooded starting battery for staring applications. AGMs are not cheap. Overall, I almost always consider an AGM a better alternative to a flooded dual-purpose battery. AGMs aside, application specific batteries are almost always a better choice.
. You can usually count on his responses to these kinds of questions to be the clearest and most detailed.<br /><br />