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Old 09-21-2004
WHOOSH WHOOSH is offline
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Starting Battery vs. House Battery

Garrett, there isn''t a different ''charging profile'' in the different form factors of conventional flooded batteries you are considering; they will charge similarly because the battery chemistry is (or should be) the same.

As you continue to work your way through Calder, I think you''ll find him also raising the question of ''battery switch management'' and whether you want that variable added to your new system. With the same basic question in front of me (but for a larger boat which needed, I felt, a larger house bank), I opted for a single house bank of 4 x 6V T105''s and a Group 27 start battery (all flooded). But the wiring plan I selected allows me to *never* need to change the battery selector switch so long as all batteries and circuits are performing properly. Consequently, I never risk e.g. running a start battery down along with the house bank because I forgot to switch back from ALL to e.g. ''1'' after doing a charge. I can start off the house bank, should that battery fail, by moving the Selector to ''2''...but otherwise, nothing changes, ever. I find this utility (and protection for self-inflicted wounds) to be very useful in the real world. It''s downside is that one needs to add an in-line sense circuit of some kind that can allow charging voltage to reach the start battery whenever the alternator is putting out...so that extra cost is the price of the simplier, more user-protected set-up.

If this interests you, visit www.jackrabbitmarine.com or give the folks there (in CT) a call and put your hands on one of Jack Csenge''s simple 12V block diagrams showing how this is set up. (This will be free, BTW). It''s simple, clever, and totally consistent with the wiring recommended for more sophisticated DC circuits (as e.g. adding wind power, an inverter/charger) at a later date.

What you doing is painful - to the wallet, the back and the hands. But it''s exactly the right kind of thing to do with an older boat, and you''ll forevermore be thankful you put your time, grit and money into this project. Good luck to you.

Jack
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