Why are marine alternators so darn $$$!

Discussion in 'OnBoard Electronics & Controls' started by ted655, Dec 23, 2007.

  1. BillyDoc
    Joined: May 2005
    Posts: 420
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    Location: Pensacola, Florida

    BillyDoc Senior Member

    Brushless alternators

    You guys might want to consider a brushless alternator like this one: www.delcoremy.com/pdfs/service_manuals/current/1G-500.pdf. No brushes, no sparks, and damn little to corrode in the internal workings. The 33SI puts out 135 amps and costs about $270 for a remanufactured unit, and (if memory serves) something like $422 for a new unit.

    The only differences between alternators that I can see is their design voltage (12, 24, 28, 48 . . .) how they physically mount to the motor and how much power they take to turn. It definitely takes more horsepower to turn a 135 amp alternator than a 55 amp one (specifically, 135 amps at 14 volts will require a bit over 2.5 horsepower, and 55 amps at 14 volts will require a bit over one.) With the regulator built in (as in this case) the alternator shouldn't mind charging "marine" batteries any more than any other kind. Assuming they are the usual lead-acid sort of technology. And as for ruining the alternator with too much load . . . I don't believe it. Any engineer that didn't include thermal protection in his design is an idiot, and I doubt anything as refined as a simple alternator regulator would have overlooked that little detail. Thermal protection means that when the unit gets too hot, the current is backed off. It's very simple to do this.

    Anyway, it's a thought.

    BillyDoc
     
  2. longliner45
    Joined: Dec 2005
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    Location: Ohio

    longliner45 Senior Member

    hey billy
     
  3. captaintrue
    Joined: Dec 2007
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    Location: here

    captaintrue Junior Member

    An alternator with low friction takes less power to turn therefore it could take less power to turn one alternator for the same output vs another. Rewinding the alternator can cause the generation of more power for the same RPM. The way an alternator works is quite simple. Most alternators can likely generate far more power than they are advertised or rated for because it the regulators that deal with this. The alternator can maybe put out more AMPS or VOLTS but the regulator might take only so much and let the rest go bye-bye in the form of heat.

    If you close up an alternator, chances are you'll need to install some heat sinks.

    But seriously, it might not hurt to get a copy of ALTERNATOR SECRETS by Lindsay publications. They really arent that complicated. And the notion of they make more automotive alternators then marine alternators so the price is more is kinda crippled logic. Alternators are alternators. Closing it up might mean making the exterior out of material that is better able to conduct heat.

    If Volvo is charging $1500 for an alternator its probably: 1) cos they can, 2) nearly if not over 50% of the price is IMHO probably warranty, 3) the extra engineering that has to go to take a 'regular' alternator and make it marine, 4) 20% of the price is probably at least just cos it says 'marine'.

    To prevent salt water problems: 1) you can coat the exterior, 2) you can close it up and provide a means of adequate heat dissipation i.e. eat sinks, fans.

    Hah and on a diesel! If its a gasoline based engine yeah you dont want the entire engine compartment enclosed--that's just ignoring the fact that an car engine compartment is basically a chemistry laboratory and a power plant all in one--that is EXACTLY WHAT IT IS.

    Think folks: even car engines arent fully enclosed they have grills and underbodies and a means for vaports to escape through nooks and crannies. Its not all that extremely complicated. You just have to look at things with your eyes open. The prospect of the compartment being flooded with water isnt a bad thing to consider. Consider that its not that uncommon to travel down a road in a car and hit a puddle and stir up all kinds of water up into the engine compartment and even flood the spark plugs or alternator and so forth. Consider that MAGNET WIRE is just like kinda sorta maybe coated with enamel to start with--you're not likely going to get the magnet wire rusted any ways--and if you're paranoid just take the thing apart and coat it with some extra varnish.

    Even auto alternators have to deal with humidity/moisture/dew/frost. $1500 for an alternator --yeah 1/2 is probably warranty, 20% is probably just "it says marine". If its made of heavier metals than cheap low--heat-conducting alloys then the shipping cost might go up and show up in the price. Enclosing the thing and adding extra fins for heat sinks or the like might add to the weight and engineering/material costs.

    Triple pulley? Oh yeahh thats such an exotic part--only on Mars right?
     
  4. ted655
    Joined: May 2003
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    Location: Butte La Rose, LA.

    ted655 Senior Member

    :D Looks like we are into the "academics" of alternators. Most of the "reasons & arguments" FOR marine grade alternators don't hold true upon close scrutiny. It boils down to 2 items really. 1. The screen inside and 2. The 2 stage regulator that will allow more than "start" only batteries to become fully charged. The rest is.... Hog Wash, as my granny would say.
    Even given the above 2 design items, this site reveals the reaming we all take IF we don't shop around. "Aftermarket Marine"
    Sailors with sore butts, quit bending over and unite! :)
     
  5. captaintrue
    Joined: Dec 2007
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    Location: here

    captaintrue Junior Member

    Good point. Regulators arent that complicated as far as electronics go. These kinds of situations with overpriced goods are just maybe opportunities to learn to do what someone else is doing for you for a steep premium.

    Oh and just FYI, here's a DIY homemade alternator for marine use (i.e. hydroelectric power): http://www.otherpower.com/scotthydro1.html

    How to keep water out? Note the how parts are 'cast' in resin or the like. Hint: guitar pickups (coils) are sometimes potted in wax. As stated above, the magnet wire is already coated in enamel because the wires come in contact with each other and one doesnt want them shorting one another out in this kind of device--suitable varnish works too.
     

  6. Frosty

    Frosty Previous Member

    Yawwwn,---sigh--- you guys can spend what you want. I am fitting automotive and wont loose a wink of yawnnnZZZZZZZZZZZZZZZZZZ
     
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