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#22
posted to rec.boats.cruising
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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 |
#23
posted to rec.boats.cruising
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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 |
#24
posted to rec.boats.cruising
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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 |
#25
posted to rec.boats.cruising
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Solar panels
"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 |
#26
posted to rec.boats.cruising
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Solar panels
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 |
#27
posted to rec.boats.cruising
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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 |
#28
posted to rec.boats.cruising
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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/ |
#29
posted to rec.boats.cruising
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Solar panels
"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 |
#30
posted to rec.boats.cruising
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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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