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Old 01-21-2015, 08:48 AM   #41
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Most battery Mfg chose a 10% recharge rate for extended life of their batts.

Charge them harder/faster and do not be surprised they dont last as long.

Most cruisers will operate 50% to 85% full to reduce charge times , unless underway.

The Mfg estimate of charge cycles also expects charge to at least 100% ,
some are now suggesting 115% recharge for longest life.

Usually onlr solar or a power hose can do this.
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Old 01-21-2015, 10:32 AM   #42
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We have dual alternators on both our engines but we also have agm batteries which can be charged at 3 to 5 times the rate of golf cart batteries.


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Old 01-21-2015, 10:45 AM   #43
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Realizing the folly of gleaning scraps of info from here and there and the dire consequences of getting it wrong, I'll now retire to pour over Calder's book and have ordered these two books which should give me a good base from which to operate from Living on 12 Volts with Ample Power and Wiring 12 Volts for Ample Power
Google Prestolite. One need not buy an expensive Leece Neville made likely on the same bench.

Dire consequences, not too likely as there are about 20 ways to do it right and within budget.
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Old 01-21-2015, 02:27 PM   #44
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I'm afraid I never had any luck with Leece Neville alternators and our Broom 42 has a Perkins M90 (4236) 80 hp engine and we opted for 4x225 amp domestic batteries charged via a 110 amp Bosch alternator through an Adverc alternator controller with a 45 amp Bosch charging a 150 amp engine start battery. 440 amps of solar panels keep us autonomous providing we use the power sensibly, ie we only use the washing machine when we're on the move or in port.
The domestic battery system powers a 4 kw inverter for freezer, washing machine etc when not in port.
More importantly the engine has sufficient torque to cope with the extra alternator and still give us 8 knots economical cruising speed.
I'm all for comfort on board but on some boats it's beginning to get over the top.
KISS.
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Old 01-22-2015, 08:05 AM   #45
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440AMPS of solar would cover a football field,

Perhaps its 440 WATTS of solar ????

Perhaps 30 amps when charging a 12v system.

Still grand for batt charging.
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Old 01-22-2015, 10:27 AM   #46
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Okay...have gone through Calder's alternator sizing guidlines for a single alternator and this is what I come up with for our boat with its 1980's equipment aboard;

450Ah (house bank) + 16 amps (DC load while running) + 25% (to ensure alternator isn't running at full capacity) = 582.5

Calder recommends, for golf cart batteries, an alternator 25% of 582.5 which is 145.625, or a 140 amp alternator.

Next to consider will be pulley ratios (from serpentine pulley kit) to ensure alternator is not providing too many amps at our engines RPM's, as well as side loading on shafts. Once this is figured out, will move onto cooler battery location out of engine room and/or ventilating battery boxes, cables, and so much more...

Interesting stuff.
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Old 01-22-2015, 12:02 PM   #47
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FF your perfectly correct, the solar panels on our boat are 440 watts NOT as I incorrectly stated amps. Apologies for the misleading typo.
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Old 01-22-2015, 02:45 PM   #48
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Realized I was off (again...) with the math.

450 (Ah) divided by 4 = 112.5 + 16 amps (DC load while running) = 128.5 + 25% (to ensure alternator isn't running at full capacity) = 160...therefore according to my understanding of Calder's theory...a 160 amp alternator should be the "best" size as long as the pulley ratio puts it in the sweet spot at our engines rpm, and if the shafts & bearings can handle it.
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Old 01-23-2015, 08:15 AM   #49
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The usual consideration is belt load.

At 150A or so dual belts are a must.
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Old 01-27-2015, 11:48 PM   #50
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At the Seattle Boat Show I noticed a Beta Marine diesel of about 50 HP that had a very nice serpentine belt driving a 180 amp alternator. They may be worth approaching for advice and hints for the setup you are envisioning.
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Old 01-28-2015, 01:25 AM   #51
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Murray

At the Seattle Boat Show I noticed a Beta Marine diesel of about 50 HP that had a very nice serpentine belt driving a 180 amp alternator. They may be worth approaching for advice and hints for the setup you are envisioning.
Thanks for the tip. According to the US Beta Marine website they use Balmar serpentine pulley kits and alternators.

Still navel gazing this issue, when time permits, which means I'm probably a year away from making a decision. Thanks again.
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Old 01-28-2015, 08:54 AM   #52
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440AMPS of solar would cover a football field,

Perhaps its 440 WATTS of solar ????

Perhaps 30 amps when charging a 12v system.

Still grand for batt charging.
Yep 440 AMPs would be about 18 large 300 Watt panels. That would be a small 5KW propulsion system.
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