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Old 18-05-2019, 13:16   #1
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2 large solar panels vs 3 smaller panels

I'm looking into stepping up my solar game. My boat came equipped with 3 solar panels totaling 370 watts that were installed in 2008. Realistically I get about 26 amps in full sun, if I push the mizzen boom so it does not shade them. They are currently running through 2 solar boost 2512i (the lower voltage version) charge controllers.

At anchor I can get about 5 days before I have to crank up the generator and recharge the batteries. My goal in upgrading is two fold - one is to hopefully eliminate this need, and the other is to run my DC watermaker off of them (pulls about 25 amps running).

I'm looking into two possible setups, one is the Hightec 200+25% solar panels, which are rated at 200 but claim to get up to 225 watts if they can get reflected light on the back side because they are bi-facial. 3 of these would produce 600-675 (50-56 amps). The only additional equipment I would need for this set up is another 2512 charge controller.

Another option is 2 Panasonic 335 watt panels, for a total of 670 (56 amps). For this I would need to upgrade to 2 3024 charge controllers. This is the more expensive option by about $400 and dimensionally these are a few inches longer and wider than my current setup.

I'm leaning toward the 3 panel setup. It seems like it would be less affected if the mizzen boom is centered, but also I can re-use some of my existing hardware. I'm not familiar with Hightec brand, but they were the highest wattage mono panel I could find that would fit in the same footprint that I have now.
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Old 18-05-2019, 14:08   #2
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Re: 2 large solar panels vs 3 smaller panels

I think you have the pros and cons about right.

Three panels and three controllers will be better if shading is an issue. The only reason to go with two bigger panels I can see is if they are easier to fit.

All other things being equal, I'd go with three panels. And for you having some of the gear already in hand, it should be an easy choice.
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Old 18-05-2019, 15:00   #3
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Re: 2 large solar panels vs 3 smaller panels

Thanks Bill, you seem to be helping me out a lot today
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Old 18-05-2019, 15:31   #4
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Re: 2 large solar panels vs 3 smaller panels

With three, if one fails or is lost or stolen or damaged, you will be left with more charging watts.
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Old 18-05-2019, 18:00   #5
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Re: 2 large solar panels vs 3 smaller panels

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With three, if one fails or is lost or stolen or damaged, you will be left with more charging watts.
Stolen??? Does that happen?
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Old 18-05-2019, 18:52   #6
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Re: 2 large solar panels vs 3 smaller panels

Definitely three. More panels with more controllers always wins. I kind of wish I would have split my four panels with four controllers instead of two.
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Old 19-05-2019, 08:33   #7
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Re: 2 large solar panels vs 3 smaller panels

Your situation is nearly exactly the same as mine was.

3 kyoceras making 370 watts when new.

2 Sunpower 360s took up only a couple of inches more on each side, and with minor changes/additions, used the same frame as what I had.

Fortunately, the wiring for the much-lower voltage Ks meant that I could use it, and my installer of the originals used a 60A controller capable of 140V; I decided, since I had the wire gauge to support it, to do mine in parallel so as to not push the top end.

Pix of that transition/upgrade are available here; email me (NOT PM!) if you'd like the entire saga from start to finish, and I'll send you all the correspondence including the product manager at Sunpower, as to how I made it happen economically. Make the title "Solar Upgrade"...

Here's the link of my upgrade:
Pictures: Flying Pig 2015-2018 Shake-and-Break-Down/Electrical Upgrade/Solar
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Old 19-05-2019, 08:44   #8
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Re: 2 large solar panels vs 3 smaller panels

I realized on my setup I really need the appropriate charger for my gel batteries bith from windmill and solar panels. This way only I have the full capacity. And also not to forget to use large currents running in my batteries in order to destroy the so called memory effect, that is ver thin metal filaments growing from one electrode to the other inside the electrolyte, lowering this way the effective charge that can be stored. For this I use my microwave that burns so much, evenfor the time to heat a cup of coffee is enough, as those filaments blow like fuses do.
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Old 19-05-2019, 10:24   #9
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Re: 2 large solar panels vs 3 smaller panels

Large solar panels are often two smaller panels in one case. If you have 72 cells it's actually 2 36 cell panels in one case if it's 12 volt nominal. Also my understanding is controllers are rated at input amperage so series would have half the amperage 24vs12. But I'm not positive about that.
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Old 20-05-2019, 15:38   #10
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Re: 2 large solar panels vs 3 smaller panels

Thanks for the advice everyone, I think I'm going to go down the 3 smaller panels route.
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