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Old 28-12-2016, 22:30   #31
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Re: matching solar panels to batteries to consumption

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Originally Posted by mitiempo View Post
Generally 80% is considered the limit for charging with the engine. It is very inefficient to charge above that approximate point as the batteries internal resistance climbs and they accept less and less current.
Yes but that acceptance rate falls off as the batteries come up whatever the charge source; diesel or solar.

It probably wont affect a small panel which will struggle to exceed the acceptance rate anyway but a bigger panels effectiveness will still be limited by the batteries towards the end of the charge.
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Old 28-12-2016, 23:12   #32
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Re: matching solar panels to batteries to consumption

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Yes but that acceptance rate falls off as the batteries come up whatever the charge source; diesel or solar.

It probably wont affect a small panel which will struggle to exceed the acceptance rate anyway but a bigger panels effectiveness will still be limited by the batteries towards the end of the charge.
Yes, the acceptance rate does fall off but that doesn't mean that the batteries cannot reach full charge on a sunny day. Makes no sense with diesel charging but does with solar.

No sense thinking there is an 80% limit if the sun cooperates.
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Old 29-12-2016, 02:08   #33
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Re: matching solar panels to batteries to consumption

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Absolutely understand your issues, I also run a traditional wooden boat. Most people have started by saying 'look at reducing consumption' and yes, this is an essential first step. I would add that with a very small electrical set up you may also want to consider going the way the Pardy's did and run things off individual batteries. So set up an LED nav light with its own battery that has enough charge to run it for 2 nights. You can even do this by running 3 separate lights in traditional wooden boxes and run them off rechargeable AA cells so you can carry some prime cells as backup. Do this for all your essentials (nav lights GPS, radio) and they you can run the luxuries like cabin lights if and when you have power. It will not be the 'most efficent' system but it may be a better solution than trying to scale a modern big boat system to fit you boat.
Precisely so. The only thing that interests me is being sure that I have nav lights and compass light, for let us say, a month at sea. The rest is nice but not essential. I had begun to think of old fashioned individual batteries (which is how my GPS works) as a back up. What you say makes good sense. Thank you. I will mull it over, cost it and get on with the next issue.
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Old 29-12-2016, 03:10   #34
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Re: Matching solar panels to batteries to consumption

Hi Sauntress,
just some info that I beleive you require to answer your question. I totally understand that you wish to operate a very simple electrical system BUT regardless of this it is my opinion that you cannot estimate your solar requirements or for that matter your battery requirements until you actually know what your exact power requirements are. Yes there has been some excellent information given here in relatioint to solar panels and batteries but neither address the actural issue of how much power do you use or actually require.
For example if you are going to use nav lights and are changing them to LED. My nav lights on a 12 metre boat consume approximatley 0.25 Amps per hour (0.25 amp/hours) If we base darkness as being approximatley 9 hours then during that time you would consume 2.25 Amphours (current multiplied by time). If your compass light is only using 0.1 amps when used we then multiply this by the 9 hours of use and come up with a figure of 0.9 Amp/hrs consumed. If this is your only consumption then add them together IE 2.25 plus 0.9 = 3.15 amp/hrs use. It can than be expected that your solar panel will be required to imput at least this amount of power during daylight hours but also the battery must be large enough to accept the loss and then be able to be charged during that time to replace what has been consumed.
I then read that you were talking of installing a Short wave radio, BIG power drain. When on but not transmitting you cosume power. You MUST be aware of your radios power consumption when on and also when transmitting to work out how much power in total you have used. An inverter also will consume power when in standby mode and have a drastic effect on your power source if not monitored.
Working out a boats power consumption is pretty straight forward and tables can be found on the internet to assist you. Before you do to much more Please work out not only your boat current power consumtion over a 24 hr period but also what it may be with the installation of a radio etc in the future. It will assist you greatly determining exactly what you require. On our boat I worked out our electrical demand was approximatley 120 Amp/hrs per day. This calculation was based on the use of the boat with auto helm, fridges, chartplotters, radios etc during a 24 hour period.
Sorry to be so long winded but it is very important. Also remember that solar is dependant on the sun, yes I know sound silly but cloudy days on end will have a huge impact on the ability of your solar panels to charge at full capacity so allow for days when you cannot get full charge in..
I hope far more elequent and more knowledgable speakers can explain this in easier terms than I have.

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Old 29-12-2016, 05:16   #35
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Re: Matching solar panels to batteries to consumption

Sounds an interesting yacht, got any photos?

To add to what Greg has said consider some form of battery monitoring device so you can see what is going on. Couple of different options available:

NASA Clipper Battery Monitor - BM1 12V Performance Monitor - Marine Super Store

Battery Monitors: Merlin Smartguage Battery Monitor (19-1001)

Personally I would join the two batteries together into one bank so the nightly discharge of each battery is halved helping to maintain the battery life. When due replacement then go for 6v deep discharge type of batteries.

Have you considered were you are going to put these solar panels? Whilst a stainless steel a frame on a modern GRP yacht is probably acceptable it will look out of place on a 1913 sloop. So you are left with deck mounting or on the life lines if she has them.

We have 110w of solar permanently fitted and a further 60w portable folding panel for use at anchor or in calm conditions. This keeps up with our daily needs including auto pilot and fridge until we have 48 hours of rain and heavy cloud or mist. Then I need to start the engine or risk taking the batteries down further than I want. The good news is the solar normally tops up the batteries by mid afternoon even with random shading from the mast and sails etc.

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Old 29-12-2016, 05:45   #36
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Re: Matching solar panels to batteries to consumption

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Sounds an interesting yacht, got any photos?

To add to what Greg has said consider some form of battery monitoring device so you can see what is going on. Couple of different options available:

NASA Clipper Battery Monitor - BM1 12V Performance Monitor - Marine Super Store

Battery Monitors: Merlin Smartguage Battery Monitor (19-1001)

Personally I would join the two batteries together into one bank so the nightly discharge of each battery is halved helping to maintain the battery life. When due replacement then go for 6v deep discharge type of batteries.

Have you considered were you are going to put these solar panels? Whilst a stainless steel a frame on a modern GRP yacht is probably acceptable it will look out of place on a 1913 sloop. So you are left with deck mounting or on the life lines if she has them.

We have 110w of solar permanently fitted and a further 60w portable folding panel for use at anchor or in calm conditions. This keeps up with our daily needs including auto pilot and fridge until we have 48 hours of rain and heavy cloud or mist. Then I need to start the engine or risk taking the batteries down further than I want. The good news is the solar normally tops up the batteries by mid afternoon even with random shading from the mast and sails etc.

Pete
More helpful comments. Yes there is room, on the afterdeck, clear of the tiller, mainsheet horse and mainsheet itself, for two panels measuring, at most 40cm by 70 cm, or but in the shadow of the tiller, a single panel 70cm by 50 cm. The batteries are currently sited in the worst possible place, in the bilges under the cockpit. They will be moved to sit under the chart table seat to port (which lifts) where they are dry, accessible and in terms of weight balance the heavy Taylors stove opposite. (just been aboard to measure this). I have a battery isolation switch, 1 or 2 or both or off already installed so yes i can set that so the power is drawn from both at once. I have (this is not your point but valid) used nothing more sophisticated for weather then BBC long wave. Which is fine for Europe, ludicrously old fashioned I know but to some extent once out there you are out there and have to take what comes. I have VHF with which to listen to the somewhat comical Spanish or other forecasts and ashore of course there is passageweather et al. I also have a Sony World short wave receiver. I would not want to run a laptop aboard, nor an inverter (I had one for a couple of months but it blew up, so that was that), but would like to be able to receive forecasts over the ether, so that is the next thing to investigate. And yes a battery monitor sounds a very sensible idea. As for photos of Sauntress, you could Google her. And take your pick. The ones I have here on this computer are too big to attach/upload not to mention being beyond my technical ability.
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Old 29-12-2016, 05:58   #37
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Re: Matching solar panels to batteries to consumption

If you have a short wave receiver then weather files are available and something like an ipad connected with a jack plug or placed nearby to receive sound all do-able without excessive use of those precious amps. This is a recent thread but there are plenty of others.

Internet-Independent Weather

This could work because I suspect you have very little other electrical noise on board. We on the other hand have fridge, electric water pump, halogen lights you just know are going to wreck any signal.

If you are looking at solar panels for the deck, folk in the UK are pleased with the new Lensun GRP backed flexible panels so far. We fitted a 30w panel last February and whilst its still early days works fine. More expensive than a rigid panel and the cheap aluminium backed panels I hope it will last longer in a saltwater environment. The connection box was the weak point on the cheaper flexible panels but the Lensun one I looked at was nicely potted so should last.

Lensun Solar Energy Store

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Old 29-12-2016, 06:01   #38
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Re: Matching solar panels to batteries to consumption

Wow




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Old 29-12-2016, 06:15   #39
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Re: Matching solar panels to batteries to consumption

You have a bit more room than may first appear. The hatch cover is an interesting space and we have our Lensun panel there because they can be walked upon with care.

Now I have attached it with 6 round circles of velcro. Will it survive a North Atlantic Winter Gale? probably not but I will have other things to think about in that situation. However it does mean that its secure in most weather conditions, doesn't need more holes drilled into the boat and could be removed in port to show off your yacht.

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Old 29-12-2016, 07:59   #40
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Re: matching solar panels to batteries to consumption

Some considerations...

Quote:
Simple math to start then you need to validate.

Some conservative assumptions:

1) useful battery capacity is 50 to 80% charged
Incorrect. The 50-80% charge cycle rule, only applies to FLA batteries, when being charged by alternator or generator (due to the extended run time to charge from 80 - 100%). As soon as one adds adequate solar, the charge cycle is increased from 50-100%.


Quote:
3) shading on a sailboat is problematic. Assume only half your panels are effective.
Better still, mount the panels where they will not be subject to shading, typically as far aft of the boom as practical (sloop rig), and assume 100% effective (ie rated output), for 4.5 hours per day average.
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Old 29-12-2016, 08:24   #41
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Re: Matching solar panels to batteries to consumption

Another good picture:

Sauntress - Classic Yacht Info

Any pictures of the keel available?
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Old 29-12-2016, 08:30   #42
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Re: Matching solar panels to batteries to consumption

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You have a bit more room than may first appear. The hatch cover is an interesting space and we have our Lensun panel there because they can be walked upon with care.

Now I have attached it with 6 round circles of velcro. Will it survive a North Atlantic Winter Gale? probably not but I will have other things to think about in that situation. However it does mean that its secure in most weather conditions, doesn't need more holes drilled into the boat and could be removed in port to show off your yacht.

Velcro Heavy Duty Stick-On Strips - Black - 2 Pack
I like the bit about North Atlantic Gales. I am quite sure one would have better things to think about (a propos there is a thread on that subject viz "have the guides got it wrong?" which when considering the east-bound crossing makes interesting reading. I think, thanks to all the advice I am nearly there now in terms of how to approach the problem of enough power. I just need to do my homework. But no holes is appealing. Thanks.
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Old 29-12-2016, 08:35   #43
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Re: Matching solar panels to batteries to consumption

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Another good picture:

Sauntress - Classic Yacht Info

Any pictures of the keel available?
Yes but not, I think in digital form. When last surveyed, the surveyor took a number of shots. It is possible I have some here on the computer. In what aspect are you interested?
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Old 29-12-2016, 08:38   #44
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Re: matching solar panels to batteries to consumption

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The 2nd thing I'd do is replace those low cap. batteries with a pair of golf cart batteries. You'll get double the cap. for the same amount of batteries and they're cheap, about $85 ea. near me.
I actually try to dissuade customers from this. If one battery shorts, the DC system is left inoperative, until the battery is replaced.

Whereas with 2 x 12 Vdc batteries, if one shorts, the DC system can be run on the other (albeit with less charge capacity) until the defective battery is replaced. In my opinion, it always good to replace all batteries at once, but few do, especially if the batteries are "not that old".
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Old 29-12-2016, 08:51   #45
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Re: Matching solar panels to batteries to consumption

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Another good picture:

Sauntress - Classic Yacht Info

Any pictures of the keel available?
Yes, I have found one but need to email it rather than attach it here.
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