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Old 25-01-2013, 22:51   #1
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Cheap, Simple Solar Panel?

Hello,


I am getting my boat ready for a trip we are planning and am thinking about adding a solar panel to the boat. She is a Cal 20, with very minimal draws on the battery. All I use is a light, small rule pump, depth sounder and to charge cellphones. I can usually get 3 days of use with a full charge.

Im trying to find the cheapest and simplest way to top up my boats batteries. I have seen some small removable panels on west marine but they got bad reviews...would really appreciate advice on what brands to look for and what size of panel i should get.

Thanks!
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Old 26-01-2013, 00:34   #2
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Re: Cheap, Simple Solar Panel?

The difficulty is always with the mounting. Many years ago on a yacht not much bigger than yours I used a 75w rigid panel that was clipped on pulpit. I only used it at anchor but dropped it down the font hatch on the v birth when sailing.

You don't need anything that big, but rigid panels are so cheap you might as well go a bit bigger. A 15-20w panel would give you plenty of power for your limited needs.
Going smaller say 10w means you may get away without a regulator, but electrical systems always expand.
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Old 26-01-2013, 03:24   #3
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Re: Cheap, Simple Solar Panel?

Check Harbor Freight and then check Home Depot if you are handy enough to homebrew your own mount. Their stuff will be cheap. They got cheap charge controllers too.
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Old 26-01-2013, 07:32   #4
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Re: Cheap, Simple Solar Panel?

V X A = W

You should never discharge your battery more than 50%

As a rule of thumb I shall say your battery is 100A, deep cycle AGM type (c $170)

100A X 50% = 50A = c72hrs @ c 1A draw (50 =/ 72). I guess your gear would drain at 1A/hr average. (A typical cabin light uses this, a cell phone would use same or less)

So I recommend a panel for you of 130W for a 12V battery =/ 10A charging

Because you need something that will have the sunlight to charge at 10A [per hour] for enough sunny hours. In this case it would be 5hours over 3 days . Not such a big target. i.e. you could put one 130W panel flat on deck for that period and hope to get 5 hours of bright overhead sun.

You need a regulator, pay $10 extra and get one which 'chases' the charging rate and adjusts the charge correspondingly. Should be c $30. Panel should be c $130, i.e. $1 per W (=/ 1A per W per hour / 12V) [see above formula] .

I'd get a nice single panel, you can use it as a sunshade! Just make a simple timber frame over or aft of the cockpit!

Unfortunatley I have a ketch. Fortunately I have a saloon deckhouse, The shade is welcome!

You can get good prices at oo.com in Oz.

Good luck!
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Old 26-01-2013, 07:55   #5
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Thanks for all the replies. Mounting is going to be the big problem, some of the powerfilm stuff looks nice, i could just set it up at anchor and take it down while we sail. I dont think there is anyway could fit a 130W panel on my boat, the boom extends from the mast right out to the stern.

I have one small area in front of the mast the would work well...or putting one one top of the sliding hatch would be the best spot, id have a bit more room for a bigger panel. Do you think 20W would be enough to charge the battery. On average the draw is probably much less than 1A/hr but that would be a decent figure to work with. Also If I mount on the cockpit slider it will be receiving sun for the entire photoperiod...unless I put the boom tent up. There is never an easy answer is there.

PS Just found the receipt for my battery, it has 650 CCA and 135 R/C

Something like this would be ideal, http://www.harborfreight.com/13-watt...ger-68750.html

I know that in all likelihood I will be selling this boat a year from now so I am trying to keep my upgrades "portable" so I can take them with me, I know I will never get back any of the money I am putting into the boat.
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Old 26-01-2013, 08:26   #6
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Re: Cheap, Simple Solar Panel?

Mount it off the stern opposite the outboard. This one is a little bigger at 80w but you should be able to mount say a 40w panel okay and it would give you a bit in reserve if its cloudy.

Quote:
Originally Posted by islander20 View Post
Something like this would be ideal, http://www.harborfreight.com/13-watt...ger-68750.html
My parents have one of those in the caravan. Works well as they leave it on the table but then they have big windows to let the light in. Also the regulator that comes with it is a simple on/off type. When I looked at the voltages it allowed a battery to go quite low before switching on which isn't ideal. A cheap PWM would be better for minimal outlay.

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Old 26-01-2013, 08:29   #7
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Re: Cheap, Simple Solar Panel?

Quote:
Originally Posted by islander20 View Post
I know I will never get back any of the money I am putting into the boat.
Word.
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Old 26-01-2013, 08:38   #8
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Re: Cheap, Simple Solar Panel?

Quote:
Originally Posted by Shanaly View Post
V X A = W

You should never discharge your battery more than 50%

As a rule of thumb I shall say your battery is 100A, deep cycle AGM type (c $170)

100A X 50% = 50A = c72hrs @ c 1A draw (50 =/ 72). I guess your gear would drain at 1A/hr average. (A typical cabin light uses this, a cell phone would use same or less)

So I recommend a panel for you of 130W for a 12V battery =/ 10A charging

Because you need something that will have the sunlight to charge at 10A [per hour] for enough sunny hours. In this case it would be 5hours over 3 days . Not such a big target. i.e. you could put one 130W panel flat on deck for that period and hope to get 5 hours of bright overhead sun.

You need a regulator, pay $10 extra and get one which 'chases' the charging rate and adjusts the charge correspondingly. Should be c $30. Panel should be c $130, i.e. $1 per W (=/ 1A per W per hour / 12V) [see above formula] .

I'd get a nice single panel, you can use it as a sunshade! Just make a simple timber frame over or aft of the cockpit!

Unfortunatley I have a ketch. Fortunately I have a saloon deckhouse, The shade is welcome!

You can get good prices at oo.com in Oz.

Good luck!

Are 130W panels down to $130?
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Old 26-01-2013, 08:41   #9
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Quote:
Originally Posted by Pete7 View Post

My parents have one of those in the caravan. Works well as they leave it on the table but then they have big windows to let the light in. Also the regulator that comes with it is a simple on/off type. When I looked at the voltages it allowed a battery to go quite low before switching on which isn't ideal. A cheap PWM would be better for minimal outlay.

Pete
Forgive my ignorance but what does PWM stand for? A regulator?
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Old 26-01-2013, 08:43   #10
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Re: Cheap, Simple Solar Panel?

Quote:
Originally Posted by Pete7 View Post
Mount it off the stern opposite the outboard. This one is a little bigger at 80w but you should be able to mount say a 40w panel okay and it would give you a bit in reserve if its cloudy.
+1

And maybe throw in a fast disconnect, to be able to store the panel in case of bigger seas.
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Old 26-01-2013, 14:03   #11
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Re: Cheap, Simple Solar Panel?

These VW solar panels may be just what you need. I use them every winter so my batteries stay topped of and do not freeze.
Fully charged batteries do not freeze

Haul Out, On The Hard, Antifoul & Winter Storage
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Old 27-01-2013, 05:15   #12
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Re: Cheap, Simple Solar Panel?

Quote:
Originally Posted by islander20 View Post
Forgive my ignorance but what does PWM stand for? A regulator?
Sorry should have explained, PWM = pulse width modulation, have a read of this and why simple on / off regulators waste alot of power.

http://www.morningstarcorp.com/en/su...Why%20PWM1.pdf

You are probably at a similar latitude to me at 50.North. when I popped down the boat yesterday in bright sunshine my two panels which total 125w of solar were generating a grand total of 1.2 amp hours, simply down to the low angle of incidence of the sun. We see 7.4AH during the summer, hence the suggestion for a bigger panel, you can never have enough solar.

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Old 27-01-2013, 05:25   #13
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Re: Cheap, Simple Solar Panel?

Quote:
Originally Posted by Tellie View Post
Are 130W panels down to $130?
Yep and even in the UK E bay prices for cheap panels are less than 1 a watt.

130 Watt Solar Panel PV Monocrystalline 12V 130W T | eBay

At these sorts of prices it pays to buy a larger panel.

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Old 27-01-2013, 06:56   #14
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I have found these guys near me,


http://www.windturbine.ca/sun_panels.html

They have panels for 1$ a W. i would like to put a large on the boat but I dont think there is any way i could fit one over 30W. I'm going to do some measuring today, mounting off the stern isn't really an option for me, the cost of the frame would be to high. Still considering the briefcase charger...not sure if it would really do much up here in the PNW.
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Old 27-01-2013, 16:22   #15
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Re: Cheap, Simple Solar Panel?

Understood, have a look a the photo half way down this page, might be an idea. He has more details on his website somewhere.

Atom Voyages - Atom's Improvement Projects Page 1

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