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Old 05-18-2019, 10:30 AM   #3
DavidM's Avatar
City: Litchfield, Ct/Punta Gorda, Fl
Country: USA
Vessel Model: Atlas Pompano 23
Join Date: Aug 2012
Posts: 5,024
Lot's to talk about in your post.

AGMs have a little different charging profile (voltage and time parameters) than FLAs so most battery chargers have a select switch to set the battery type.

The 2 or 3 step charging modes are a different setting and I suspect the two step just switches the charger off when it meets the absorption criterion. For AGMs I don't see why you would want to do that. Just keep it in 3 step so it will float at a low 13.5V or so value to keep the batteries fully charged.

The alternators in most marine engines are regulated to produce one single voltage, about 13.5 like the float mode on the charger. As a result they don't do a good job of fully charging. But if you are back at the dock after a couple of days on the hook, the shore power charger will charge up the batteries completely, so no problem.

Only if you stay on the hook for a week and cruise to another place every couple of days would I worry about alternator regulation. Some say you can modify the existing alternators to accept external regulation. This can be done, but you are asking a lightweight alternator to perform as a heavy duty one and you may burn it out prematurely.

I would much prefer getting a heavy alternator like the Leece-Neville with external regulator terminals or a more expensive high output Balmar alternator and regulator.

Finally, the OEM alternators won't hurt your new batteries but they won't charge them up fully either. An ACR isn't the right device to deal with this issue, a new alternator/regulator is. Sterling does make a device that can help and it doesn't require external regulator terminals, but I would first see how what you have works first before doing anything.


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