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Old 08-04-2014, 08:26 PM   #39
thomasonw
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City: San Juans, WA
Vessel Name: Viking Star
Vessel Model: 45' Monk / McQueen
Join Date: Apr 2014
Posts: 34
Hello. Congrats on the new boat, and being in the PNW. There is a LOT to do up in the islands! You mentioned Crusaders so that really limits you a lot - being gas engines. You really need to make sure you get proper marine alternators that have the needed explosion protection.

One thing you might do is consider your usage. Cruising the San Juan's you likely are just an hour or two between stops (or more if you slow it down). Even at our slow pace a 4-hour trip was unusual unless we were repositioning the boat. If you mostly do weekend cruising the engine alternators will not help you while at the dock/anchorage, and are not really needed on the return trip to home port (as the shore power charger will top off the batteries). Perhaps just try things a bit and see how it goes? After you understand your cruising pattern a bit you can decide where the weaknesses and opportunities are, alternators, battery size, generators, solar, etc.

It seems a lot of these posts have talked about other options, many of which are applicable only to Diesels. FWIW, we have been using large frame Leece Neville alternators for several years now. At this point I have a 270A/12v LN4870 alternator on the main. It is able to put out 120A+ at idle for hours on end, and we get upwards of 220A underway (Limited due to slow cruise RPMs).

I purchased it off Ebay for around $200; new ones are available for under $400. A cover plate can replace the existing regulator to allow an external regulator to be attached (part number: 39-5204, 100265, or A038100265S). I originally used a Balmar external regulator, but had issues with it exiting Acceptance Mode early - well before the battery was recharged. Perhaps the newer ones are different, but after a trip up the Columbia/Snake where I had to stop and restart the engine to get the regulator to continue Bulk/acceptance charging I pulled it for a fixed voltage truck regulator. Last summer I started using an Arduino based multi-step regulator I developed and posted in public domain.

I have been reading some good things about later model 'hair-pin' alternators, ala the Desno units that many Chryslers and some GM cars have been using for the past few years. Thinking about picking one up for our DC generator and see if it is indeed more efficient. If you have a Diesel I think there are lots of options out there. Gas is another story.

Best of luck deciding which way to go. Remember, if you upgrade the existing alternator to look also at the wire to the battery, don’t just reuse the existing wiring harness w/o verifying it is heavy enough for the current. And looked at some of the boats you build, wow. What a great life to have!

-al-
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