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Old 22-10-2010, 18:12   #16
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I would start with making a list of your electrical needs and then with a list of the options of juice makin'.

Going for incandescent (cheaper) or LED (more expensive) and choosing energy efficient appliances will allow you to save on battery sizes.

On some boats a basic alternator is all that is necessary - because they can plug in every night in the marina or at a dock.

If planning any longer trips, I would leave the alternator as it is (as long as it is at least 50-55 Amps and investing in a proper regulator for it.

If this is nearly good enough but not quite - upgrade the alternator.

If this is not enough, solar panels, windgen or a genset will be necessary or a combination of them. Fuel cells perhaps.

Going for deep cycle batteries for the house use makes a lot of sense (they do not have to be AGM nor gels, but do NOT use starting batteries for the house bank).

Going for a good starter battery (e.g. the toilet rolls by Optima) makes a lot of good sense to me too.

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Old 22-10-2010, 20:28   #17
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[QUOTE=skipmac;545976]First, a proper, smart regulator will not shorten the life of a battery. In fact I believe data shows that a well charged battery will outlive a constantly undercharged battery.[QUOTE]

A smart regulator matched with the wrong size alternator (too large) will infact shorten the life of a battery. Under charging a battery is simply a symptom of not charging long enough, nobody has advocated not charging the battery to full. A smart regulator doesn't know the charge rate, only the battery voltage and the amount of time the charge is applied. It then uses it's internal knowledge of the battery type (as you programmed it) and makes a decision on how much voltage to apply to the field of the alternator. No magic.

You can chose to do what you like with your batteries, but when a reader asks, I'm going to tell them the design characteristics of the system. Flooded deep cycle batteries will most likely last 2-3 years with abuse, or 6-8 years when treated as designed.

If you want fast charging batteries, buy AGMs. There are plenty of folks who will argue the time saved charging more than pays for the upcharge to AGM. Everyone has different needs, for my use case, I don't see the savings.
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Old 22-10-2010, 21:03   #18
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[QUOTE=DotDun;546061][QUOTE=skipmac;545976]First, a proper, smart regulator will not shorten the life of a battery. In fact I believe data shows that a well charged battery will outlive a constantly undercharged battery.
Quote:

A smart regulator matched with the wrong size alternator (too large) will infact shorten the life of a battery. Under charging a battery is simply a symptom of not charging long enough, nobody has advocated not charging the battery to full. A smart regulator doesn't know the charge rate, only the battery voltage and the amount of time the charge is applied. It then uses it's internal knowledge of the battery type (as you programmed it) and makes a decision on how much voltage to apply to the field of the alternator. No magic.
You can always create a screwball system that will fry batteries, or any other part of a system. I am posting comments based on the assumption of a properly designed and installed system, not screwed up, badly designed system. I am assuming the OP is not interested in that kind of charging setup.

So, again assuming a proper system, you will charge batteries faster with a larger alternator and smart regulator and without damage. Using a standard automotive alternator/regulator system it would be almost impossible to fully charge a battery due to the tapering off of the charge as the battery charge state increases, battery voltage increase and the internal resistance of the battery increases. Unless motoring for hours you will never fully charge a battery with an automotive regulator and to put many amps back into a large, deep cycle battery will take hours of engine time, especially with a 65 amp alternator.

A smart regulator will pump a lot of amps into a very low battery to bring it up to a much higher percentage of charge in a much shorter time. Much less wear and tear on the engine and crew.

A smart regulator particularly with battery temp sensors will also reduce charge to a rate that will not damage the battery as it reaches a fuller state of charge.

Also a smart regulator will include an equalization feature that will allow max topoff of the battery and reduce sulfation when you can run the engine long enough which is acknowledged to increase battery life.

And even if you don't agree with all the above you have to admit that a smaller, dumb alternator/regulator will take much longer to charge a battery, all other things being equal. So it still comes down to, do you prefer to wear out a $20,000 engine or maybe reduce the usable life of a $200 battery.

That math seems pretty plain to me.


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Old 22-10-2010, 21:23   #19
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Quote:
And even if you don't agree with all the above you have to admit that a smaller, dumb alternator/regulator will take much longer to charge a battery, all other things being equal.
I would go start with the smart, multi-stage regulator and battery temperature sensing. You may not need a high capacity alternator, because if you have a suitably sized house bank, and you typically allow around 25% depletion (50% max), then you won't spend much time charging at high amperages.

Example, I have a 105 amp alternator, but rarely will the charge regulator allow it to deliver more than 50 amps to my house bank for any period of time. After the first few minutes the charge rate is usually less than 50 amps and declining. Once it goes into acceptance mode, I shutdown the engine and let the solar panels take over.
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Old 23-10-2010, 05:32   #20
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Originally Posted by skipmac View Post
And even if you don't agree with all the above you have to admit that a smaller, dumb alternator/regulator will take much longer to charge a battery, all other things being equal. So it still comes down to, do you prefer to wear out a $20,000 engine or maybe reduce the usable life of a $200 battery.

That math seems pretty plain to me.


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We agree on the value of the smart multi-stage regulator.

Where we disagree is advising the OP to go against battery manufacturer's recommendations for rate of charge. The OP deserves to know that continually exceeding the manufacturer's recommendations for rate of charge will shorten the life of the battery. One can justify doing so any way they like, but the OP deserves to know the facts such they can make up their own mind.
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Old 23-10-2010, 05:56   #21
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" it says a 98 amp hour Alternator is $338 and a 90 watt solar pannel is $415"
Mark, shouldn't that read "1411 watt Alternator" to compare watts to watts on the solar panel? <G>

15.6x more power coming out of the alternator for 22% less cost.
Oh, yes theres a watt difference.

But I never use the engine to charge the batteries (the engine batt excepted). Sitting at anchor or sailing its all solar. I never run the engine. So i save on a few hours engine per day. At todays deisel price he would pay for the solar panel in 6 months out of you deisel usage

I would assume this guy could do the same. Unless I live in another world... a parallel universe inhabited by tanned sailors on boats with solar panels.


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Old 23-10-2010, 11:35   #22
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I have seen many boats killing their batteries because the banks were too big for the charging capacity of the boat. Going for SMALLER banks would have resulted in longer battery life.

So, if you decide you need X amt of energy and X size of batteries make sure you do have the charging capacity on board.

Also, I have seen very few boats with too small alternators but countless boats with only the basic 'car' regulators. OK for the starting battery but way too inefficient for the house bank.

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