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Old 17-12-2010, 12:02   #16
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Originally Posted by delmarrey View Post
Normally one does not want to take a battery below 75% anyway making a 100 A alt. fairly useless on a boat with only 2-3 standard automotive batteries. That's why I stated way early, and referring to a different thread "Unless you have a large battery bank (e.g. 1000 Ah) it would be over kill."
I'd take exception to the point above -

it's normal to run a deep cycle lead acid battery down to 50% discharge, then recharge battery to 80-85% of capacity; this keeps the charge rate at it's maximum efficiency (e.g., most power accepted by the battery per unit time). It's also normal to couple a hi-output alternator with an external regulator that is observing battery state (temperature, voltage).

I have used an Ample Power 105AH 12vDC hot-rated alternator controlled by Ample's external regulator, since 1994. I typically see that alternator kicking out 85-90 amps for 90 minutes at a time while recharging a 450AH battery bank (4 x 6v deep cycle golf cart batteries) when passage making I try to charge twice a day, once in the morning and once in the evening.

And yes, that alternator is in the engine room, along with the engine, and it does get hot

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Old 17-12-2010, 12:25   #17
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Here are some posts that might be of interest from an expert to deals in charging systems.

AGM and gel-cell performance notes

How "fast" you can reliably charge your battery.

Evaluating 12vdc Flooded-Cell Batteries

Understanding a model for battery charge acceptance

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