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Default Solar panels

In article ,
says...

"Glenn Ashmore" wrote

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at:
http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com


I like the idea of diverting to the water heater, but most of us do not have
the option to add a second 12V element to our existing heaters.

One thought, would be to add a second heater in an external loop around the
water heater - something like the add-on heaters that are sold for cars in
lieu of a block heater. This site has the elements:

http://www.realgoods.com/renew/shop/...204/ts/1025078

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

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Default Solar panels

bob wrote:
Marine water heaters typically have two heating devices in one package.

The first is a standard 110V electrical heating element, connected

thru a thermostat mounted on the tank, more or less just like your
standard domestic water heater.

The second heating device is a coil of tubing inside the tank thru
which you can circulate your engine coolant.


Hi Bob,
Actually I was curious about the 12 volt heating device someone had
mentioned they had in theirs - would that one come with, or have
provision for inserting a thermostat or temperature sensor? Thanks
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Default Solar panels

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



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Default Solar panels

First of all 150 watts of panels is not going to produce 430 AH. You would
be very lucky to get 300 or so. If you can produce 56 AH/day extra just
leave the refrigerator running and have the cold beer ready and waiting for
next weekend. A half way decent refrigeration system should keep cold
without being opened on 50 AH a day.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"GBM" wrote in message
...
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





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"GBM" wrote in news:BeTzg.53656$Uy1.27051
@read1.cgocable.net:

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


Once again, use the controller in PWM mode. Solar panels don't need a load,
only devices like wind generators do.

-- Geoff


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Sailaway wrote:
bob wrote:
Marine water heaters typically have two heating devices in one package.

The first is a standard 110V electrical heating element, connected

thru a thermostat mounted on the tank, more or less just like your
standard domestic water heater.

The second heating device is a coil of tubing inside the tank thru
which you can circulate your engine coolant.


Hi Bob,
Actually I was curious about the 12 volt heating device someone had
mentioned they had in theirs - would that one come with, or have
provision for inserting a thermostat or temperature sensor? Thanks


I followed the link posted by others and looked at the elements - they
look more or less exactly like standard 110V or 220V elements do - that
is, they do not have an integral thermostat. If your plan was to
install the 12V element in addition to an existing 110V element, then
you would need another thermostat as well. And perhaps even more
importantly, you would need another threaded tank penetration into which
to screw the element.

bob
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Default Solar panels


"Glenn Ashmore" wrote
First of all 150 watts of panels is not going to produce 430 AH. You

would
be very lucky to get 300 or so. If you can produce 56 AH/day extra just
leave the refrigerator running and have the cold beer ready and waiting

for
next weekend. A half way decent refrigeration system should keep cold
without being opened on 50 AH a day.


You are right Glenn - 150 watt panels will probably not produce 430 AH. But,
according to this link it should have been about 405 AH:

http://www.qsl.net/ve3lgs/solarpnl.htm

My neighbour at the marina has the problem I described and has recommended
we either install just one 75 watt unit or more batteries. I don't like the
idea of running the refrigeration just to consume power . It gets everything
quite cold in about 2 hrs anyway, once we get to the boat.

Can't the controller simply switch off the current from the solar panels
when the batteries reach full charge?

GBM


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Default Solar panels

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/
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"Geoff Schultz" wrote

Once again, use the controller in PWM mode. Solar panels don't need a

load,
only devices like wind generators do.


Not all controllers have PWM.

I am considering a marine kit made by Soltek in British Columbia. It comes
with their own controller called a GPR-22 - also sold for RV use under Go
Power name.

The company packages this controller with their kits and presumably it is
satisfactory for basic systems and presumably cuts out panels once batteries
reach full charge and cuts back in at some lower voltage.

GBM


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Default Solar panels

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
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