Matt,
6hrs at 240watts or 8 hrs at 150 watts - either one would heat water by
about 100F. But what was the water temperature when you started?

If the engine had not been run, it might be say 80F, so we get 180F - not
enough to boil, but enough to scald anyone opening a faucet.

If the engine had been run, the batteries could very well be fully charged
and the hot water tank hot - lets say 150F. Now we anchor and put 240 watts
into the tank for the next 6 hrs. Now the water IS boiling!

Whether or not this is a real world problem, depends on how the boat is
used. For live-aboards or those on extended cruises, it is likely not an
issue. But, for weekend cruisers it could be.

Suppose we return from a long weekend cruise and the batteries are low. We
don't have shore power and rely on the solar panels to recharge the
batteries unattended during the week. We get 8hrs/day for 5 days of bright
sunshine on our 2x75watt array - about 430 Amp hours and we have a 200AH
bank plus starting battery that need a total of about 150AH to recharge.

In a case like the above will the charge controller safely cut off current
to the batteries? Or should we cover the array?

GBM

"Mark Borgerson" mborgerson.at.comcast.net
wrote
GBM wrote:

But, if the solar panels put out, say 150 watts for 8 hours, what
happens
when the water becomes too hot? With a small boat type water heater say
6 or
10 gal, this could happen quite quickly. Maybe then we throw the towel?

According to this handy calculator:

http://chuck-wright.com/calculators/watts.html

Heating 6 gallons of water by 100F will require about 240 Watts
for 6 hours. You're not likely to boil the water in in
the heater with that amount of input. With losses, 6 hours
at 150Watts is probably just enough for a hot shower. OTOH,
on a day sunny enough to give you 150 Watts for 6 hours,
you probably don't need a HOT shower. ;-)

Mark Borgerson

Geoff Schultz wrote in
6:

What you need is a regulator that runs in diverter mode.

Naw.....What you need is a TOWEL to throw over the panel to keep it in the
shade at the dock. What's that cost? $1.39?....(c;

Larry wrote:
Geoff Schultz wrote in
6:


What you need is a regulator that runs in diverter mode.


Naw.....What you need is a TOWEL to throw over the panel to keep it in the
shade at the dock. What's that cost? $1.39?....(c;

That is what the book says as well!

Gary

Gary wrote in
news:5Y7zg.278047$Mn5.49928@pd7tw3no:

Naw.....What you need is a TOWEL to throw over the panel to keep it
in the shade at the dock. What's that cost? $1.39?....(c;

That is what the book says as well!

Gary



I suppose, in keeping with the "nautical motif", we should have a custom-
made blue cover with a ship's wheel, anchors or flags boldly emblazoned on
the cover with the boat's name underneath for, say, $350?

Naw, belay my last.....that old towel that we found in the lazerette will
do....

Just toss it over the panel and hold it down with a few "empties". After
all, this IS the party boat, right? We must keep up appearances to
maintain our status!

Larry wrote in news:Xns98109EBC3AAC7noonehomecom@
208.49.80.253:

Geoff Schultz wrote in
6:

What you need is a regulator that runs in diverter mode.

Naw.....What you need is a TOWEL to throw over the panel to keep it in the
shade at the dock. What's that cost? $1.39?....(c;


That's a good plan until you forget to do so or they blow off and you cook
your batteries. Hey, those batteries only cost you...oh a lot, lot more than
a controller. Send the bill to Larry! He told you that you don't need
one...that's your choice. You're the captain and pay the bills.

My water heater accepts 2 heating elements. Ones 120V and the other is 12V.
I know other people who have large resistors that they divert power to. Of
course they get hot, but it works.

-- eoff

Gary wrote:
Is anyone familiar with "self regulating solar panels"?

Quote from: http://www.solaronline.com.au/page/technical_notes.html

"A self-regulating module has a limited number of cells connected in
series, normally 30 or 32. This limited number allows the module to
only produce a maximum of 14.5 Volts, thus making it difficult to
overcharge the battery.

Using a self-regulating module does not automatically assure that a PV
system will be self-regulating. Battery capacity, use of the loads and
temperature must be considered. Generally, self-regulating modules can
be safely used when the battery capacity is large. If the capacity is
small, there is still the possibility of overcharging the battery."

That being said, self regulating panels are much less efficient in a
battery charging application, as the charging voltage is considerably
lower than a regular 36 cell module.

Mark wrote:
Gary wrote:

Is anyone familiar with "self regulating solar panels"?


Quote from: http://www.solaronline.com.au/page/technical_notes.html

"A self-regulating module has a limited number of cells connected in
series, normally 30 or 32. This limited number allows the module to
only produce a maximum of 14.5 Volts, thus making it difficult to
overcharge the battery.

Using a self-regulating module does not automatically assure that a PV
system will be self-regulating. Battery capacity, use of the loads and
temperature must be considered. Generally, self-regulating modules can
be safely used when the battery capacity is large. If the capacity is
small, there is still the possibility of overcharging the battery."

That being said, self regulating panels are much less efficient in a
battery charging application, as the charging voltage is considerably
lower than a regular 36 cell module.

Thanks. What I am trying to find out here is if anyone has any first
hand experience with self regulating solar panels.

Gary

In article uVSyg.273940$IK3.20678@pd7tw1no,
Gary wrote:

Is anyone familiar with "self regulating solar panels"? I would like
to hear from someone who has installed one without a regulator and
how well it keeps the batteries up.

Not sure what size you're talking, but we have a 12w panel on our 120AH
(used one-at-a-time) banks. It keeps the active battery up quite well
for mostly 3-day weekends with a few multi-week trips each season. We
have full voltage after 4-5 days away, almost never start the engine to
charge, and the panel will bring a flat battery up enough to start our
Yanmar 2GM by mid-morning.

In two seasons, it brought a weak battery back to life, yet I need to
add much less water than I did before.

We're quite happy with the system.

Our demands are obviously light, so you mileage may vary.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

Jere Lull wrote:
In article uVSyg.273940$IK3.20678@pd7tw1no,
Gary wrote:


Is anyone familiar with "self regulating solar panels"? I would like
to hear from someone who has installed one without a regulator and
how well it keeps the batteries up.


Not sure what size you're talking, but we have a 12w panel on our 120AH
(used one-at-a-time) banks. It keeps the active battery up quite well
for mostly 3-day weekends with a few multi-week trips each season. We
have full voltage after 4-5 days away, almost never start the engine to
charge, and the panel will bring a flat battery up enough to start our
Yanmar 2GM by mid-morning.

In two seasons, it brought a weak battery back to life, yet I need to
add much less water than I did before.

We're quite happy with the system.

Our demands are obviously light, so you mileage may vary.

Thanks for the on topic response. The panel I have is a 46 watt panel
and I will be running it into two 100 amp batteries. It produces a
maximum voltage of 14.6 and maximum of 3.6 amps. I was wondering just
how self regulating it would be. Do you leave yours on all the time?

Gary

In article 2cfAg.306263$iF6.139599@pd7tw2no,
Gary wrote:

The panel I have is a 46 watt panel and I will be running it into two
100 amp batteries. It produces a maximum voltage of 14.6 and maximum
of 3.6 amps. I was wondering just how self regulating it would be.
Do you leave yours on all the time?

Ours is on full time. All indications are that it isn't overcharging
the 120 AH battery.

I no longer parallel even "identical" batteries for any length of time.
If one of them is slightly weaker, it will likely go south.

My preference would be to install an 8D or a couple of big 6v in series.
Doubt that panel would hurt either of those.

Of course, I'm talking without knowing anything about the
self-regulation. If it actively limits the current at high voltage,
you're safe. If it simply has a diode to keep from draining the battery
at night (like ours), you are less protected, though a max of about 50
watts is easily dissipated.

BTW, expect your panel to perform better than the numbers, as they rate
for what they expect after a few years' service.

As I think, with a max 15 volts, you probably have active regulation,
since modern cells are designed to charge even when slightly shaded.

Keep track of things for a bit. If you have to add water quickly, your
panel is too big for the battery, so get a bigger battery. It's tough to
have too many AH.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/