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Lew Hodgett Lew Hodgett is offline
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First recorded activity by BoatBanter: Jul 2006
Posts: 348
Default Clueless in (not Seattle) Amps, etc.-Update

Lew Hodgett wrote:
Skip Gundlach wrote:

I'm obviously missing a great deal of intelligence here.

I had thought we'd properly sized our bank and input sources to allow
for our anticipated usages.

Obviously I was mistaken; I need a large-frame alternator and the
appropriate drive components, in order to only bring my bank to 90%.


Wet cell batteries are a very mature technology.

The rules for them are very simple.

1) If you want to consume 200AH/day, you must generate 250AH/day of
replacement energy.

You can play all kind of regulator games, but in the end, the overall
average replacement rate is about 15% of the bank capacity or in this
case, 15%(750)=112.5A.

The minimum recharge time will be: 250/112.5=2.2 hours.


The only way to reduce the recharge time is to increase the size of
the battery bank which in turn allows for a higher recharge rate.

Still no free lunch, but does reduce the recharge time.

Batteries to a cruising sailor are like clamps to a wood worker, you
can never have too many.

How you choose to get it done is your business, but the above rules
define the task.

Solar:

For an engineering estimate, use a 2ftx4ft,80W panel which translates
into 10W/sq ft.

Derate 50% for dirt, clouds, angle of attack, etc, thus 5W/sq ft.

As a year around average use 12 hours/day, thus 12hours(5W/sq ft))=60
watt-hours/sq ft/day.

60watt-hours/12volts=5amp-hours/sq ft/day.

To generate 250AH of solar you need 250/5=50sq ft or at least 7 2ftx4ft
panels.

Probably not going to happen unless you build a hard bimini so you have
a place to plant your solar garden.

That's why alternators like the L/N 4800/4805 family exist.

Modest size, only 145/165 output depending on model, but either deliver
in excess of 100A at 2,000 alternator.

Ya pays ya money, ya takes ya pick.

Lew