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post #2 of Old 02-03-2005
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High capacity alternators

Wayne, out in the cruising fleets it''s hard to find a boat over 10M LOA that hasn''t switched to some form of upgraded alternator. To avoid expense and the potential for serious bearing wear (on the crank and raw water shafts), you''ll want to stick with a small-frame upgrade. And within that general category, you have 3 basic choices:
1. Buy an off/shelf ''HiCap'' alternator, either from a manufacturer or via a vendor (e.g. Jack Rabbit Marine; nice folks & very helpful with all the ''extra'' issues)
2. Have a marine/auto electric shop wind you a new HiCap unit; by taking in your stock unit, they can match the form factor (case & pulley dimensions) and wind the alternator to your requirements (e.g. 108 amps, hot rating); this will cost perhaps 40-50% less than a ''real'' HiCap unit but it won''t produce as much low-end output (e.g. charging while at anchor and engine in the 1000-1200 rpm range); you do get something extra for that marine price <g>
3. Buy a HD alternator from a car dealer, intended to support one of the high-end cars with lots of accessories and modify it; e.g. if you have a Yanmar diesel, it will probably have a 55 amp Hatachi alternator...but Nissan will have in the dealer''s parts shop a 80+ amp Hitachi alternator intended for perhaps a Maxima; this will require you to find a bored parts employee who doesn''t mind pulling a few boxes and comparing his high-output alternators with your ''sample'' off your engine; this will cost you perhaps 1/3 the price of the marine HiCap unit.

I''ve done each of these and had good performance in each case; there''s a certain amount of personal preference involved. In each case, you will still need to externally regulate the alternator and this is where the complexity comes in; in the case of the e.g. Nissan/Hitachi alternator, you will need to split the case and jump out the internal regulator - any shop can do that for you.

There are many product choices for both regulators and also battery monitors/controllers. IME the best route when delving into this arena, before buying anything, is to ID a vendor that you would like to work with and then explore the choices you prefer and how they can help you. That''s why I mention Jack Rabbit Marine; they are good folks and have been doing this for a long time ( tho'' they are only one vendor among many.

It goes without saying that you will have already done all your reading, done an energy budget for your type of boat use, and have a good feel for the related issues (charger, perhaps inverter & controller, battery bank monitoring and capacity, etc.). This is one of those areas where you want to have the whole forest under consideration before starting to cut your trees...

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