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Old 12-04-2017, 01:40   #1
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HELP: Specific solar advice wanted on our set-up

Hello everybody,

First and for all: We (the wife and me) have been reading a LOT on this forum and elsewhere on the subject of solar energy. We're both university graduates, but there's just too much information out there for us to come to a decision regarding our particular solar purchase...

We've been hit with terminology such as diodes, MPPT, series, parallel, mono, poly, MC4, sunpower, etc... All of it completely new to us. We just know we want as much as green power as possible.

Therefore, we would like some specific advice from you guys for our specific situation. We know a lot of information can be found elsewhere, but we're just a bit overwhelmed right now (also a lot of other works on the boat going on such as wind generator, anti-fouling, replacing rudder bearings, re-doing the floor etc etc). So please don't shoot us for asking about things which can probably be found elsewhere...

We have a Beneteau 411 and currently a custom tailored arch is being manufactured by a local stainless steel magician in Cap d'Agde, France.
(you don't want to know how long we've been searching for a guy like this)
The arch will be finished next week, and therefore we need to decide on which solar panels to buy SOON since our guy will be making a custom frame for them:-)

We have following available space on top of the arch:
BxL = 1,20m x 2,80m = 47,2 inches x 110,2 inches

Of course we would like to maximize the amount of watts, therefore we might deviate a bit on the available space, but for sure a solar panel of 1,44m would be too big (would interfere with the bimini, which we like to take away at times). BTW: What's better: more watts with lower efficiency or less watts with higher efficiency rating ?

I've only read good thing about high efficiency sunpower cells so we decided to search these panels. We found these (german made) panels with sunpower cells: Shipping these to France would be very cheap and fast.

Do you think these are a bit too pricey ? Would these ( comparable panels -without sunpower cells but a lot cheaper- be almost as good ? Specs seem to be the same almost?

We're doubting between 4 or 5 of either of these panels. So far, so good. But then our hell starts: Which MPPT to buy and where to place it since it seems to produce a lot of heat ? Does every MPPT has two outputs ? One for housebank and one for start battery ? Is this needed? How to wire the panels (serie, parallel..), what is a diode and where to place it, do we need it at all?, which wires to use and how thick should they be, also keeping insurance in mind (we read about "marine grade" but not clear what this is), what fuse do we need for this setup (60 amps?) and where to place it, which inverter would be sufficient etc etc.

If ANYBODY has a better suggestion (completely different panels or whatever), please: tell us ! The offgridtec panels seem to have a lot of white spots -> unused cell space ??

We currently have a housebank of 4 x 110 Ah and a start battery of 100 Ah.
In the future we will probably expand this capacity.

We have a 12 volt watermaker which I'd like to run every two days and plan to install a microwave and an SSB which will consume a lot.

Sorry for our stupid questions guys, but we're in way over our heads here and are unable to find a local guy giving us some simple and clear advice :-(

If anybody could give us a A-Z complete system advice, this would be greatly appreciated and obviously rewarded with lots of belgian beers ! :-)

PS our budget is maximum 1500 euros (1600 USD)
Thanks a lot !

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Old 13-04-2017, 14:21   #2
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Re: HELP: Specific solar advice wanted on our set-up

Okay, lots of questions.

The 100w Sunpower solar panels you linked to are also available here:

I have just bought the 150w panel from them, wasn't Sunpower put German Solar World, hopefully still better than the cheap Chinese made panels on e bay. However, only time will tell.

I suggest the next thing you need to work out is a power budget of all the things you plan on using. Tow columns on a spreadsheet would be good, one for at anchor and one for sailing. That should tell you how much solar you need and define the size of your battery bank. There is lots good advice on here about this.

In terms of series or parallel might be worth reading this:


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Old 13-04-2017, 14:30   #3
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Re: HELP: Specific solar advice wanted on our set-up

Why are you looking at 12 volt DC panels.

You want the max watts per square meter panel you can fit regardless of voltage, I use 63 volt panels (Sun Power), then let the solar controller look after the 12 volts conversion.

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Old 14-04-2017, 10:10   #4
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Re: HELP: Specific solar advice wanted on our set-up

I was recently considering similar setup for my Beneteau 343:

- For solar most Watts is what you need. Higher efficency means the same Watts come in a smaller and often lighter footprint.
- The expensive 1.06m x 0.54m 100W panels you suggest at 7kg vs the cheaper 1.2 x 0.54m at 8.8kg. That is 35kg vs 44kg for a 5 panel array.
- If you can stretch to 2.88m wide you could use 4 of the 1.44 x 0.54m 140W pannels from that same vendor. Lengthways across so array is 2.88m *1.08m. 560W would be the peak output in perfect conditions - clear sky, intense sun, cool panels, angled exactly toward sun
- domestic 250~300W panels are cheaper per Watt and the MPPT takes care of the voltage reduction to 12V charging

MTTP regulator:
- Outback Flexmax 40 is good quality and reasonable price. Max 520W PV input power. About 250 euros. Another 40 euro for the remote monitor
- These aren't much more expensive than the Chinese "Tracer" range that seem to get good reviews and I was considering before Outback had a cheaper unit than their 60A
- Locate the MTTP near the batteries. High current output so you want thick short cables (<1m)
- Recomendation seems to wire in series-parallel. So the two panels on each side wired in series and then the two sides wired in parallel to the MTTP.
- Series works best in low light. Parallel works best if one panel shaded so this assumnes shading will happen to both panels on each side

VSR Voltage Sensitive Relay Split charge fully automatic
- 12V 140A will cost about 30
- These take care of charing the starter battery first and then when it is charged will join the house bank
- will never let your lights/microwave flatten your starter battery

1000W inverter. about 100~200
- Should power most small 700W microwaves and even small power tools.
- 1000W output, say 85% efficent draws 1000/0.85/12 = 98 Amps. Again short thick cables to the house bank and 100A fuse or breaker
- 10 minutes use is 10/60*98 = 16 Amp hours out of your batteries.
- 1/2 hour is 50Ah that is 25% of you house bank.
- You don't want to drop under 50% charge and you need to put more in as the charging and storage of the batteries have losses

I rejected building an arch for 500~600W of fixed panels (using two of the big high voltage domestic 250~300W) as my wife thinks they look too ugly and I kind of agree (especially on a 35 foot boat where we are summer-time live-aboards).
We have seen lots of Bimini mounted semi-flex panels recently and I will go down that route as the semi flex panels are a lot cheaper than they were a few years ago.
Four of 100W (1 x 0.55m) in two banks of 200W each side and these banks in parallel into the 40Amp MPPT.
Store them under the V-berth when not in use (over winter and in storm conditions when we drop the bimini to minimise windage and reduce chance of shredding).

If those panels are good I will likely add another 2 removable for flip-up on the side rails. If I exceed the 40A limit with these 2 extra panels (unlikely in real conditions) then I will add a cheap 20A MPPT on the extra two.
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Old 14-04-2017, 17:39   #5
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Re: HELP: Specific solar advice wanted on our set-up

Originally Posted by azul_b View Post
I was recently considering similar setup for my Beneteau 343:

1000W inverter. about 100~200
- Should power most small 700W microwaves and even small power tools.
Careful about that one. Microwaves are advertise as there output power.

A "700W microwave oven" will draw more than 1000W. And running through an inverter, your actual battery consumption may be 1500W or more. (i.e about 120 Amps)
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Old 15-04-2017, 01:28   #6
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Re: HELP: Specific solar advice wanted on our set-up

Yes need to be careful the inverter will work with the microwave - not only the power is enough but the sine wave generation is good enough also.

Here is a example of matched tested set 1000W inverter plus 600w compact microwave 250.
microwave oven and 12v 1000w inverter combo pack suit caravan camper motorhome | eBay.

Looks like same inverter can be found for only 80

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solar, wanted

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