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Old 01-14-2021, 11:23 AM   #1
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Solar Panels for winter trickle charging

Hello,

I am hoping that somebody has experience with keeping their batteries topped off over the winter with use of solar panels. I am hoping that there is enough opacity in my shrink wrap to temporarily install a solar panel on my cockpit roof to maintain my batteries.

Does anybody have experience with this? Any product recommendations?
My boat is a 1999 Albin 33+3 Express Trawler.

Thanks!
Paul.
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Old 01-14-2021, 12:09 PM   #2
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I doubt that the shrink wrap would let enough light through to do much charging. I've never tried it, though.
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Old 01-14-2021, 12:50 PM   #3
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If you use a big enough panel, say 100 watts, you will get enough power to keep your batteries up even with the shrink wrap.

Install a 100 watt panel on the roof and connect it with 10 or 12 gauge MC4 cables to a PWM solar controller. Then connect the output of the controller to the batteries or to a cigarette lighter outlet. Make sure you fuse it at the battery end with a 10 amp fuse.

These can be bought for about $135 for all on Amazon:

https://www.amazon.com/HQST-Monocrys...s%2C684&sr=8-6

https://www.amazon.com/Renogy-Wander...xpY2s9dHJ1ZQ==

https://www.amazon.com/Renogy-20FT-1...s%2C185&sr=8-6

https://www.amazon.com/SEACHOICE-127...s%2C223&sr=8-9
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Old 01-14-2021, 03:59 PM   #4
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I have 700 watts on the "roof" covered by white shrink wrap. It does not get enough light to trickle charge. I was sure it would. I do have a guy coming to take a look at it. Should have an answer sometime in the next two weeks and will post it here.

Rob
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Old 01-14-2021, 05:42 PM   #5
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Quote:
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I have 700 watts on the "roof" covered by white shrink wrap. It does not get enough light to trickle charge. I was sure it would. I do have a guy coming to take a look at it. Should have an answer sometime in the next two weeks and will post it here.

Rob
I installed 700w in the fall then wrapped the boat a few weeks later and turned on the charger. I've been meaning to run a test. Will report back in a few days. I have to think there's some power available.
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Old 01-14-2021, 07:23 PM   #6
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Jeff,

I am getting power but about .4 amps at 12 volts. Seems like it should be more.

Rob
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Old 01-14-2021, 07:32 PM   #7
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If you are seeing low amperage, is it possible that your batteries are fully charged and the solar controller has switched to float mode of about 13.5 volts which will only push less than an amp to keep them up?

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Old 01-14-2021, 09:17 PM   #8
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If you are seeing low amperage, is it possible that your batteries are fully charged and the solar controller has switched to float mode of about 13.5 volts which will only push less than an amp to keep them up?

David
Thanks David I do understand that. My gauge on the solar controller is showing a low state of charge. I have a trickle charger connected now. As mentioned earlier I hope to get the tech out there in the next week or two.

Rob
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Old 01-15-2021, 01:53 AM   #9
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What about hanging the solar panel on the outside of the shrink wrap?
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Old 01-15-2021, 07:00 AM   #10
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A sitting LA batt , depending on age , will discharge internally between .5 % and 3% of its capacity per day .

Figure the capacity (20 hour rate) of you batt set and decide how large the system needs to be.

For our needs the XANTREX C12 PWM Solar Charge Controller was large enough and has some advantages.
$75. or so .Was labeled Trace when purchased , worked for about 15 years till boat was sold.

It can easily be set for the voltages you prefer which will differ in summer and winter ,
it will monthly do a heavier over charge to get rid of sulfation if desired..
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Old 01-15-2021, 09:28 AM   #11
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I have been using an el cheapo solar panel from Harbor Freight to keep my 2 batteries charged in my 17 ft center console here in Florida. I bungy it to the swim platform. This has worked for 3 seasons now, but the panels are cheap and don't last long.
I'm doing the same on my travel trailer. Thy don't put out much, but they keep the batteries topped off.
If I had a boat cover or shrinkwrap I would tape the panel to the outside. That shrinkwrap tape is pretty strong stuff.
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Old 01-15-2021, 11:22 AM   #12
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I have a group 24 and a 27 on my rag boat. FWIW I just disconnect them both so less fire annd discharge risk and they never lose more than .25 or .50 volts from fall to spring with boat on the hard. Also no worry about faulty solar controller discharging battery. Might work for you big boat guys on the hard too.
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Old 01-15-2021, 12:07 PM   #13
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I have a group 24 and a 27 on my rag boat. FWIW I just disconnect them both so less fire annd discharge risk and they never lose more than .25 or .50 volts from fall to spring with boat on the hard. Also no worry about faulty solar controller discharging battery. Might work for you big boat guys on the hard too.
Letting a battery discharge by 0.5 volt which is about 50% can result in sulfate sloughing off from the plates and reducing capacity and ultimately shorting the plates. I always keep a trickle charger- solar or plug in, on my boat and RV batteries during the winter storage months to avoid this.

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Old 01-15-2021, 12:45 PM   #14
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Solar Charging

I have 750 watts on panels on my pilot house under shrink-wrap here in the Northeast. Does a perfect job of trickle charging and keeping all my batteries at 100 %

Henry
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Old 01-15-2021, 09:04 PM   #15
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Here is a picture after several sunny days. Charging but the battery is low. Getting the Apple tilt
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IMG_1166.jpg  
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Old 01-16-2021, 07:45 AM   #16
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"Letting a battery discharge by 0.5 volt which is about 50% can result in sulfate sloughing off from the plates and reducing capacity and ultimately shorting the plates."

Yes , one of the differences between start and deep cycle batts is the deep cycle plates are shorter so this gropsch has a place to collect and wont short out the plates.
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Old 01-16-2021, 09:42 AM   #17
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I have a 130 watt solar panel on the cabin roof, common for Cutwaters. It has a Sunsaver duo solar controller so it charges both house and engine battery banks. Keeps my batteries topped up nicely. I'm in float now, so I see about .5 amps on a sunny day. If the batteries were discharged at all I would see more.
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Old 01-16-2021, 06:37 PM   #18
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I turned off the charger and let the house bank discharge slightly to see what kind of power I could get under shrink wrap from my 700w setup. 330 wh today, peaking at 84 watts. My rough estimate is 10% of uncovered power.
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Old 01-16-2021, 07:38 PM   #19
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Would uncovered power be 700 watts in the winter in the Great Lakes. I doubt it. With the midday sun at 40 degrees I bet you won't get much more than 350 watts. So 84 ain't bad, about 25% of uncovered.

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Old 01-18-2021, 12:01 AM   #20
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I think the daily yield is more meaningful. Today I got 150 wh. So in two days of bulk charging I got about 500 wh.

I turned the charger back on. Experiment over!
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