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.

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

On Fri, 27 Jul 2007 19:37:37 GMT, Lew Hodgett
wrote stuff
and I replied:

snip

I agree largely with you Lew, but I reckon that you are being a bit
_generous_ with the solar panels' capabilities.

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.

Human bevaviour: Bestiality with a brain

OldNick wrote:

I agree largely with you Lew, but I reckon that you are being a bit
_generous_ with the solar panels' capabilities.

That is why it was called an "engineering estimate"

If you vary more than a few degrees from the equator, you will need
more panels for sure.

Lew

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

On Jul 31, 12:38 am, Lew Hodgett wrote:

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

How about 2 alts and 2 banks, use the banks alternately so one is bulk
charged while the other is absorption charged at the same time. Plenty
of redundancy too.

Maybe 2x 75A alts and controllers are cheaper than a 150A alt and
controller.

Also solar will work better with a bank that is between 50-85% state
of charge.

cheers,
Pete.

On Thu, 02 Aug 2007 04:29:11 -0700, Pete C
wrote:

Maybe 2x 75A alts and controllers are cheaper than a 150A alt and
controller.

The battery bank in question is close to 800 AH and can not be
recharged from 40 or 50% depletion in a reasonable length of time by a
75 amp alternator. The main cost of the 200 amp alternator is in the
installation work, also an issue with a dual alternator set up.