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Old 03-05-2016, 07:13 AM   #21
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2-12volts and a seperate bank for cabin?
No generator...but considering building in a small Honda for power.

A size 31 start batt , or a pair if you operate below 32F , and some sort of house deep cycle batt would be std.

How you operate the biggest hassle , refrigeration, will decide if 2 6v golf cart batts or 8 are needed.
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Old 03-05-2016, 09:30 AM   #22
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I'm trying to decide how big an alternator to get for the DD. how big a battery? 2-12volts and a seperate bank for cabin?
No generator...but considering building in a small Honda for power.
My $0.02...

I think too many people consider bigger is always better for alternators -

I think it depends a lot on how you will be using the boat

If you cruise for extended periods and have a gen a smaller alt is more than adequate. If you spend extended periods on the hook the gen gives you batt'y recharge capacity w/ no need to run main eng.

If you need to run an inverter w/ large loads while on the hook w/ no gen or while cruising then a larger alt may be appropriate.
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Old 03-05-2016, 11:17 AM   #23
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Originally Posted by prairieoyster View Post
I'm trying to decide how big an alternator to get for the DD. how big a battery? 2-12volts and a seperate bank for cabin?
No generator...but considering building in a small Honda for power.
Our 26-foot trailer boat cruises the Inside Passage, anchoring 75% or more of the nights. We have no generator, and no high amp consumers of power like air conditioning or electric stove. We do have a windlass, but run it only with the engine running. Summer in the north doesn't even require much use of cabin lights. Refrigerator is by far our greatest AH user.

Your AH needs will be dependent on what equipment you use, and for how long between recharges, which also depends on your cruising area and habits.

When we designed our electrical system, we determined the amp draw of each device that would be run while at anchor, and estimated how long each of these devices would run. Multiplied together to get amp-hours, added all those up, and came up with a conservative (high) estimate of 60-70 AH per night at anchor. We used an Excel spreadsheet to make this much easier, as it does take some repeated re-calculation to get it reasonably correct. Would be happy to share if you like.

We have a Link 2000 battery monitor, so we have a good handle on actual AH usage: 30-60 AH per night. Our house bank easily handles one night, usually handles two in a row pretty well, and can squeeze out three on occasion if we need to.

Rule of thumb is that house bank AH capacity should be at least 3X the AH requirement between recharges. Our two g31 12V AGM batteries provide 210 AH, and were the most we could physically squeeze in (a pair of 6V golf cart batts could have worked). We'd like to have maybe twice as much AH capacity, but just cannot fit it in. Your beamier Tolly might have room.

Well matched with a 210 AH house bank, we have a 75A Balmar alternator, with MaxCharge external regulator. It easily recharges the house bank in 1-2 hours underway. It could handle a bank twice as big pretty well.

Our start bank is a pair of the smaller g34 AGM's, for a total of 1760 CCA, which work well to start our 260hp Volvo KAD44P diesel. They get recharged in a few (10-20) minutes, much like those in our diesel pickup.

We also have 30A shore power, so at marinas we usually plug in to keep batts fully charged, and allow use of a small electric heater, and the electric side of our hot water heater.
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Old 03-05-2016, 09:42 PM   #24
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Too bad you couldn't use one of these engine / generator / AC compressors.

Hatz Aircon APU, diesel generating set, power generator¬*- HATZ Diesel

It is air cooled, so no hull openings to cut or worry about clogging. Just pull ambient temp air down to the aircon and blow it back out.

It provides 8 kw cooling and 55 amps of power at 24vdc and burns about 2.1 liters of diesel per hour.

If only it had a clutch controlled hydraulic pump on the engine too...

Long life, diesel, combination AC & battery generation. Not a bad combination.
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Old 03-06-2016, 07:02 AM   #25
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"I think too many people consider bigger is always better for alternators -"

What most folks need is usually a SMART V regulator instead of a big dumb alt.

The single wire units stink at reducing the hours spent waiting for the house batts to recharge, by design .

Dumping the single wire alt and using a 3-4 step V reg may cut charge times by over half.

AS many use the Motorola foot print a rebuilt car alt with remote V reg wiring can be had at Auto Zone for tiny bucks.

75AH was common on old Caddys and Olds.
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Old 03-07-2016, 08:03 PM   #26
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any idea why there would be 2 temperature sensors plumbed into the water pump.

Can I run 2 identical gauges from the same sender?
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Old 03-12-2016, 12:06 PM   #27
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any idea why there would be 2 temperature sensors plumbed into the water pump.

Can I run 2 identical gauges from the same sender?
One for a gauge and one for an alarm?

Only if the sensor is designed for two gauges.
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