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wwilson 02-03-2005 08:22 AM

High capacity alternators
I''m considering replacing the stock alternator on my boat''s auxiliary with one of larger capacity (100-150A). I''ve done the due diligence and know most of the pros and cons. I''d be interested in hearing the plus and minus from any, who care to comment, who have actually MADE the switch to a larger alternator on their boat.


WHOOSH 02-03-2005 08:56 AM

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...


fer@fer 02-03-2005 12:12 PM

High capacity alternators
Hi Wayne.

As you see, you don''t even finish to think your question, but Jack answer is almost already posted. Ha ha ha!!

Ok. I have gone through that.
1. Is not the same putting a 150 A alternator to a 115 perkins than to a 28 hp volvo. So I assume that if you are considering a 150 A piece, your auxiliary is closer to 100 HP rather than to 30.

In any case, if such piece of alternator is to be charging 60 Ah o greater current for more than 15 minutes (This is replacing a 50 % depleted 450 Ah bank), you should consider having twin pulleys, good ventilation for the case, and assurance of the varnish quality in the windings. Implicit is the requirement of a good three stage external regulator.

Having said that, the forest, as Jack describes, is a very complex and expensive instalation, involving not only the electricity side but also the engine too. Now I would like to discourage u in trying to reduce your budget by US$ 100 or 200 in the alternator piece, since the value of the forest may be 100 times that. This mean that I followed the number 1 route suggested by Jack.

However, my 110 Balmar run by a 60 HP VOLVo, has only one pulley. Meaning that I almost never want my 450 bank be depleted in more than 40/50 Ah between charges. (I still carry 10 replacement belts onboard, and when the RPM needle stops is the moment to stop engine and replace the belt) Any time at all i''ll upgrade the pulleys.

Regards to u both


wwilson 02-06-2005 06:57 PM

High capacity alternators
Jack & Fernando – much thanks for your thoughtful and very helpful responses to my post.

Jack, I am very much aware of the position the alternator plays in the electrical system as one of multiple integrated components and agree with your, “forest for the trees” caution. In fact, this project could easily spread to other components and I’m not sure that is worth it to me. You offer some very interesting alternatives to the obvious “bolt on a Balmar” approach that I had not thought of. I will explore them – thanks!

Fernando, you touch on at least one point for my hesitancy about the move to a high capacity alternator. Frankly, keeping a stock of 10 spare belts on board and replacing them frequently may be more annoyance than running the engine longer or more frequently to my style of sailing (enjoyment - I’m not a live aboard). Also, I was interested in your assumption that my auxiliary must be in the 100 HP range, given my interest in 100 to 150 A alternator. Mine is a 55 HP Volvo. I expect a 150A alternator to draw slightly less than 4 HP to run at its peak output. The stock alternator is drawing approximately 1.8 HP (calculated). Accepting those estimates (for the sake of discussion) the difference is an additional 2 HP load on the diesel. I would have expected this to be only marginally noticeable, if at all.

Another concern (paranoia?) is the increased side loading on the various shafts. Mine is a single belt installation. All the additional belt tension required to transfer those 4 HP from drive shaft to alternator will be shared by each shaft on the belt. Over time, that will take its toll on the water pump – first seals, then bearings. Any experience with how long that inevitable bit of “erosion” will take? A dual belt solution is certainly possible, but not inexpensive!

I’m not trying to talk myself out of the upgrade – there’s just enough engineer in me to be suspicious of the “something for nothing” that, “bolt on a Balmar” assumes.

WHOOSH 02-07-2005 02:56 AM

High capacity alternators
Wayne, you really have little to fear from upgrading your alternator so long as you keep it a small frame unit and don''t expect huge gobs of output from it. The reservations you ''should feel'' IMO have to do with having an overall system that allows you to really benefit from upgrading the alternator - the ''ripple effect'' from the HiCap alternator that moves to external charging controller and a battery monitor (e.g. Link) system of some kind.

When this conversion is done poorly and/or a huge alternator is mounted with a single belt, problems with belts and and pump shaft seals (not to mention alternator mounting brackets) can emerge...but these are not common with the less ambitious installation you plan (assuming it''s done well), and especially given your description of your type of sailing. The kind of loading you have computed for your engine seems reasonable to me, and your engine is clearly up to the task given its rating. I fear that Fernando''s 10 belts is symptomatic of his installation rather than a predictor of yours.


sailnaway 02-11-2005 08:00 PM

High capacity alternators
Last year I bought a Balmar with the smart charger it was for my old Atomic 4. I installed it and after three hours of trying to figure out if it was working and programing it with the little magnetic screwdriver to activate the micro switches we set sail for a day run to Ft Mayers from St Pete. We pulled in and I always do a system check befour I shut down and guess what dead battery in fact all them were low but the cranking battery was dead. The Balmar had failed just after we hit the Gulf and we motored most of the way to Ft Mayers. The computer that powers the system had died. I checked the voltage from the ALT and nothing ?????? I checked every thing and nothing. I called tech support and I was told that if the brain dies the ALT would not put out any voltage 0. I took it back and got my money somewhere around $400 back put the old 35 Amp on and sailed on and it is still ticking. I could not begin to understand why someone would design a piece of equipment for thr cruiser that only worked with the box they sell if the ALT still put out at least you could get the batteries hot and even wire in an old regulator to get by on. Technology can be your enemy I am just getting into all this gizmo crap. I have been sailing since 1965 and never had any of this stuff but I like the gadgets but I want them to work.

windship 02-17-2005 03:20 PM

High capacity alternators
I upgraded to a Balmar 115A alt. and external adjustable regulator./The whole deal cost me just under $500.00.
Later that season I also installed a wind turbine. Since then the Balmar just sits there looking pretty. The turbine does the whole thing, all seven batteries and it does it while I''m not there! As a result, most of the time my alternater is shut of leaving more power for the engine.


Mkfcdl 03-01-2005 12:01 PM

High capacity alternators
I have a question along these lines. I have a 56hp Yanmar with the stock Hitachi alternator (single 1/2" belt). I have a large (880ah) AGM bank + AGM starter, a wind generator (LVM Aerogen 6), and a 12v generator (Panda 4kW). I was thinking of upgrading my alternator, not so much because I need more output but so I could externally regulate it (I have a Link 2000R). However, when I looked closely at the Hitachi it is an 80amp (cold I assume) alternator, not the 55amp version. Since it seems to work so well (5 years old, happy as a clam and only one belt change needed the whole time), maybe I only need to have its internal regulation converted to external capable? Or, since I have such a large bank, is it really pointless to externally regulate it anyway on a sailboat? To give you an idea of how much the alternator is used, the engine has 150 hours in 5 years of sailing. Any comments would be great--Thanks.

boatbum 03-01-2005 02:52 PM

High capacity alternators
Mark, the best thing you can do is externaly regulate it with a new three stage regulator. It will bring the bank back to full status where as a standard automotive type will take forever to do it. Any alternator shop can rig it for you, leaving the wires for you to attach an external regulator. You will be pleased.

jdanzig 03-03-2005 06:11 AM

High capacity alternators

I have a very similar battery bank to you. Also 880ah. Realize you don''t use your engine a lot however the 80 amp alternator is very small for that bank. For comparison I have a 270 amp alternator [dual belt] that is externally regulated Link 2000R and electronically limited to 220 amps when living aboard or 150 amps when in weekend cruising mode. You need to be able to throw enough amps into that large of a bankto properly charge. Don''t remember the exact recommended ratio but something on the order of 25% of capacity.

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