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maestro 03-01-2006 11:27 AM

battery system upgrade
as i sit here and contemplate my house/starting battery system, I was lookinh for some comments on what works best. I currently have a 2 bank system. Starting Battery (bank 1) and Group27 105 AH house battery. My house battery is nearing the end of its life and was thinking about replacing it with 2 6 volt. golf cart batteries. (huge increase in AH's) I charge the batteries with a 70 amp alternator from the engine as well as an 15 watt solar panel for the house and a 5 watt tricle charger for the staring batt.

Does this sound appropriate??

WHOOSH 03-01-2006 05:22 PM

Maestro, this is one of those issues with lots of wrinkles and laden with personal preference; only the basics are true science. First, we need more info on use of your house bank. E.g. when the boat is used regularly, what's the boat's typical energy budget inbetween dock plug-ins? E.g. how many amp/hrs do you consume each day, and do you spend nights at anchor or on a mooring vs. being plugged in. Also, knowing you have a 70 amp alternator doesn't say anything about how the battery is charged, since most alternators are not regulated externally and so after only a few moments, a partially depleted battery is only getting a small charge, even from a big alternator. Finally, say a bit about your boat. If you have a 24' overnighter you only daysail, your bank is probably fine the way it is. If you have a 36' sloop you plan to sail on all summer long, the 220 amp/hrs of capacity in one dual 6-volt bank might prove inadequate (especially as you add more systems over time).


maestro 03-01-2006 06:10 PM

Jack, I have a 28 ft coastal cruiser which I spend the entire summer living on (nice to be a teacher). While at my YC the boat is on a mooring so dock power is not an option. While on vacation it is probably 50/50 anchoring vs. marina with power. I put in at least a 1-2 hour motor trip each week to keep the batteries topped up (that with the 2 solar chargers) have worked fairly well the past 2 seasons. My biggest draw of power are my lights (both running at night and interior lighting...although I try to not use the lights as much, it still becomes a draw) I was planning on adding radar within the next yuear or so. That was why I was considering upgrading the house batts this get ready for next year as well as get a little more out of the electrical system.

Am I wroung to want to make this change?? Should I stya with what I got?? 1 starting batt and 1 12v house batt??



PBzeer 03-01-2006 06:35 PM

If you have a 3 stage regulartor, the batteries will charge much more efficently. Nothing wrong with adding AH if you can keep it charged. With more amp hours, you are drawing down less of your total available, so the batteries won't get as low. Usually better to have more of something than less! Especially if you plan to add more toys. That's my understanding of it. But I'm no expert.


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