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Old 10-29-2013, 10:41 PM   #1
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Hi Amp Alternators

Question,
I am new to the large boat ownership. I have a 34' Tollycraft with two start batteries, four house deep cycle. I am having a bunch of work done on the boat and am wondering if a high amp alternator is a good idea. Currently the alternators that are one the Crusaders are 55amp. What are your thoughts? Most of our time will be spent at State parks up in the San Juans. Your feedback is appreciated.
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Old 10-29-2013, 10:57 PM   #2
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bshillam, I look forward to this discussion. I need a recommendation for 130 amp alternators and external regulators. I dont want the answer to be Balmar. The cost is BS.
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Old 10-29-2013, 11:04 PM   #3
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I have a start battery and two 200 amp house batteries, plus an electric bow thruster but no electric stove, heater, or air conditioner on my 35-footer. The 100++ amp alternator (sans genset) takes it all in stride.

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Old 10-29-2013, 11:23 PM   #4
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You should ne able to find some bolt in alternators in the 75-95 amp range that won't cost mega $$.
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Old 10-29-2013, 11:24 PM   #5
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I assume you have a gas galley and fridge? Your power requirements will dictate how you plan to charge the 12v system. In the San Juan's there is not much power at the Wa State parks. Do you have a generator on the tolly? A lot of people pickup the little Honda gens that are quiet and they run them to top the batteries off. I have read many strings on battery charging and I am sure you are going to hear it all depends on what you are using, how much power it takes, how long you want to sit still, how far you will be moving, etc. Do you want to start your main engine to charge a battery? With our setup, electric galley and multiple fridges, I have to run the generator for several hours a day to keep them up.

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Old 10-29-2013, 11:41 PM   #6
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A good resource for you to look over that covers the subject well.

The West Advisor: Alternators
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Old 10-29-2013, 11:53 PM   #7
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One reasonable approach is to match your alternator output to your battery bank and your expected running time.
If your house bank capacity is 450 amp-hours and your batteries are flooded lead-acid, conventional wisdom recommends that you don't use more than half the capacity before recharging. Your useable capacity between charges then is 225 ah, or maybe 2 days use on the batteries if you use your refrigerator.
If you use your existing self-regulated alternators, their charge curve is not very good and it would take several hours running to recharge -- they won't actually put out 55 amps, and they won't put out a consistent high charge rate. That's just the way self-regulated alternators work.
Flooded lead-acid batteries won't accept a charge higher than a certain level without boiling the batteries, and that rate is around 20-25% of their amp-hour capacity. For your hypothetical 450 ah bank, you don't want to charge at a rate much beyond 100 amps anyway, and that will give you a 2 1/4 hour recharge time for 2 days' use.

Some ways to do that include:

Externally regulating the alternators you have with a regulator that can control both alternators to charge one bank, with provision for an echo charge on your starter bank. Balmar and Ample Power both used to have regulators that will do this. The combined output would probably be close to 100 A, for a run-time of around 1 1/2 hour per day of battery use.

Put one 100 A alternator and smart regulator on one engine for the house bank, and leave the other 55 A for the start bank. 100 A is the recommend max for a single V-belt, run time will be around 1 1/2 hour for a day's use.

Get a Go-power 100 A charger and power it with a Honda generator. Your run time would basically be the same 1 1/2-2 hours per day of battery use, and the charger would keep your banks topped off at the dock. This also gives you AC power on the boat and gives you redundancy if somehow both banks become depleted. Although use of a gas-powered generator on board is somewhat controversial, this option may give you the most capability for the dollars.

Install a generator.

Forget all this, change all your lights to LEDs, and use an Engle Fridge-freezer to freeze blocks of ice which you then put in a cooler or in your un-plugged refrigerator.

If you have to replace the house bank and have the money, you might consider changing to AGM batteries and putting in 2 high-amp alternators, since AGMs will accept a much higher charge rate. This would give you a running time of maybe 45 minutes per day of battery use to recharge.

If you run on the plane, your legs in the San Juans won't be very long -- an hour would get you between almost any 2 points. Even at trawler speeds the legs aren't long, often not long enough to provide the necessary charge time.

Any way you go, many will recommend a battery monitor as a first step, so that you can accurately track your usage and recharge rate.

I have 1 125A Ample alternator with an external regulator to charge a 700 ah battery bank. We use 50% as our maximum discharge and use a generator to recharge if we aren't motoring. The other alternator is self-regulated and charges the starting bank, with the ability to interconnect the banks to start or charge either bank from either engine.
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Old 10-30-2013, 01:25 AM   #8
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Av8r, Great summary of the feasible choices.

Here's another good source for additional info:

Installing a high power alternator in your boat
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Old 10-30-2013, 06:52 AM   #9
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Alts are expensive and there are many partial truths from sellers.

A rebuilt Delco from Auto Zone can be had very inexpensivly ($30 bucks) made for an external Regulator ,
65A is any old Caddy. 1960 era

The key to all is an external regulator which tells the unit to charge fast and much better than the auto profile of a stock one wire V regulator .

Balmar , Les Tech or Ample power re-wounds or rebuilt alts suffer from low hot ratings so using a good V regulator will do little after the first 10 min of operation.

Its a big PIA but a real full sized 135+ (two foot) alt from a truck store will create its rated output hot , and will cost a fraction of a marine rewound.

This might require a second pulley on the front of the engine to use dual belts.

So the order of purchase would be first the SOC meter.SO you know whats happening .

Then a rebuilt Caddy 65A alt with good V regulator .Too cheap not to try with a modest batt set.

The removed alt. would be fine spare .

IF the run times are too long as you cruise , should you add batteries , the final step would be the bigger full sized alt, controlled by the better V reg. .

As second full sized alt belted of a noisemaker will complete the set for a big battery cruiser that loves the Sound of Silence.
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Old 10-30-2013, 07:24 AM   #10
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Quote:
Originally Posted by FlyWright View Post
Av8r, Great summary of the feasible choices.

Here's another good source for additional info:

Installing a high power alternator in your boat
I am confused, the article posted by FlyWright says the alternator should produce about 25% of the batteries capacity in a charging scenario, give or take.

However, I have just installed a new Victron, Inverter/Charger and according to the Victron engineer I spoke to they maintain the charging rate for lead acid batteries should be between 10-15 % of battery capacity.They reduced the Victron's charging capacity to my battery output.Anything above 15% is not recomended.

Is there a difference between charging through an alternator and a battery charger?
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Old 10-30-2013, 07:39 AM   #11
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Quote:
Originally Posted by Andy G View Post
I am confused, the article posted by FlyWright says the alternator should produce about 25% of the batteries capacity in a charging scenario, give or take.

However, I have just installed a new Victron, Inverter/Charger and according to the Victron engineer I spoke to they maintain the charging rate for lead acid batteries should be between 10-15 % of battery capacity.They reduced the Victron's charging capacity to my battery output.Anything above 15% is not recomended.

Is there a difference between charging through an alternator and a battery charger?
May have to do with multi-stage charging and what voltages they charging unit is producing.

All to often we the customer has to figure out the apples to apples info as manufacturer's sometimes speak only from their reference point.
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Old 10-30-2013, 09:21 AM   #12
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Great info regarding alternators... one thing the O.P forgot to mention is weather the boat is gas or diesel???

Many of the truck alternators are not sealed explosion proof units and as such should not be used in a gasser..

HOLLYWOOD
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Old 10-30-2013, 10:12 AM   #13
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Summit Racing sells a shockingly (no pun intended) large selection of alternators in 6, 12, 12/16 & 24 volt applications with sizes ranging over 200 amps.

Someone may find something useful there.
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Old 10-30-2013, 10:35 AM   #14
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... Do you want to start your main engine to charge a battery?...
That's a good question. Running your gas Crusaders to charge your batteries? The Honda 2000 to charge your house bank for ~$1K doesn't sound like a bad deal.
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Old 10-30-2013, 10:39 AM   #15
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Originally Posted by hollywood8118 View Post
Great info regarding alternators... one thing the O.P forgot to mention is weather the boat is gas or diesel???

Many of the truck alternators are not sealed explosion proof units and as such should not be used in a gasser..

HOLLYWOOD
I'm an ex Tollycraft owner (also a 34'), while I owned it I also wanted to up my alternator size. Hollywood is correct, very few higher output alts are suitable for a gasser. I spent a lot of time looking into this and had to lower my expectations, educate yourself before you buy anything.
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Old 10-30-2013, 10:59 AM   #16
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Originally Posted by FF View Post
Alts are expensive and there are many partial truths from sellers.

A rebuilt Delco from Auto Zone can be had very inexpensivly ($30 bucks) made for an external Regulator ,
65A is any old Caddy. 1960 era

The key to all is an external regulator which tells the unit to charge fast and much better than the auto profile of a stock one wire V regulator .

Balmar , Les Tech or Ample power re-wounds or rebuilt alts suffer from low hot ratings so using a good V regulator will do little after the first 10 min of operation.

Its a big PIA but a real full sized 135+ (two foot) alt from a truck store will create its rated output hot , and will cost a fraction of a marine rewound.

This might require a second pulley on the front of the engine to use dual belts.

So the order of purchase would be first the SOC meter.SO you know whats happening .

Then a rebuilt Caddy 65A alt with good V regulator .Too cheap not to try with a modest batt set.

The removed alt. would be fine spare .

IF the run times are too long as you cruise , should you add batteries , the final step would be the bigger full sized alt, controlled by the better V reg. .

As second full sized alt belted of a noisemaker will complete the set for a big battery cruiser that loves the Sound of Silence.
FF, I have read the suggestion for dual pulleys several times on the forum. I have a Cummins with a surpentine belt. Is the dual pulley necessary in my case for a 130 amp alt?
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Old 10-30-2013, 11:19 AM   #17
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My engines are gassers. Right now we envision taking about a two hour trip to one of the islands and staying a night if not two. We have a frig, 12v diesel heater forced air, water pump, and thats about it. I would say we're not heavy 12v users. No TV when boating. I also have a gen set but would like to run that as little as possible. Maybe run it in the late after noon for hot water showers? I have a dedicated battery for the gen set. So there is a lot of redundancy in the system as it stands. It's easy to get to the alternators now since the engines are sitting on the side of the boat. But I am trying to prioritize as there are a lot of things coming into the picture that need attention.
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Old 10-30-2013, 11:40 AM   #18
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Bshill:
the most important part of your charging system is the regulator. You need to know how many amps are going into your batteries, and for how long. Likely your 55 amp alternators are internally regulated. this will allow 55 amps for a very short while, enough to replace the single digit no of amps used for starting the engine, but will then drop off and give you only 10 or so while idling or up to 15 or maybe 20 for a while while running. this is not adequate for battery charging on your fridge bank. Unless you have a DC only fridge, that load alone justifies a bigger alternator and a good, three stage regulator. Also check your genset/charger system for a decent regulator. that is just as important as on the alternator side.
I recommend at least 100 amp charging, on both the alternator and generator. If you don't have an inverter, get a smart regulator (Balmar is good, Ample Power is good, there are others) that will put out 100 amps continuously, in "bulk" mode, and drop to a trickle when 90% charge is achieved. If you are buying an inverter/charger, the same spec regulator should be in that system too. Every amp used has to be put back into your batteries.
If you can't get the alternator/charger output to the batteries, you have not solved the power supply problem.
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Old 10-30-2013, 01:20 PM   #19
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>FF, I have read the suggestion for dual pulleys several times on the forum. I have a Cummins with a surpentine belt. Is the dual pulley necessary in my case for a 130 amp alt?<

No not at all the flat belts are used to get over the limitations of even big B sized V belts.

Heat is the enemy during rapid recharging so any improved big buck V regulator should have a temp sensor to install between the batts where ever the ventilation is poorest
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Old 10-30-2013, 01:20 PM   #20
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At this point I guess I'll stick with the 55's as it appears we'll be using the 12v very little other than frig and heat. I have four golf cart batteries and I would be happy with two days of reserve. Specially if I just have to start the gen set to get the water hot for about a hour a night. Probably go with the most conservative approach - use the boat and go from there. If I have to add high amp alternators later than so be it.
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