Solar installation write up

Discussion in 'Installation Photos/Specs' started by HallOfDreams, Sep 24, 2019.

  1. HallOfDreams

    HallOfDreams Member

    37
    Sep 11, 2019
    2003 (2004 face lift) Searay 340 8.1L Mag. Outdrive.
    Mercruiser 8.1L 496 mag
    I thought I would share my knowledge of solar installations on boats with you. I hope you all find some good info here.

    In the last 5 years I have done 3-4 installations and gained a lot of info on what works and what does not work so well, technology has moved on at quite the pace, panels have got small, flexible and charge controllers more efficient with high outputs.

    PWM charging
    Starting with the basics. There are a few concepts of solar charging, the most common is wiring panels in parallel thus harvesting the highest output in amps and feeding this to a basic pulse width modulation charge controller. The sum of the output from the panels will be no more than the amount the batteries need to draw or has available to draw. PWM controllers also will start to restrict the amps being flowed into the batteries as the battery becomes more charged.

    Here are the plus and minuses of the basic method of solar charging using parallel wiring and PWM controllers.

    Pros –
    Charge controllers are cheaper!
    Oh that’s it really.
    Cons –
    Very thick cables required to run from solar panels to the charge controller making hard to hide (and costly).
    Less output
    Bottle neck charging as the batteries get full.
    One panel out of sunlight the whole array becomes inefficient.

    MPPT Charging
    Then along came MPPT charge controllers (Maximum Power Point Tracking). To save a huge lesson in electronics for those that don’t know. MPPT controllers turn unused voltage (for boats anything over 12v) into amps. They also track optimum voltage outputs. For MPPT set ups it is best to wire your panels in series (output = sum of all volts produced, amperage sum of single output of panel) But wait are we not wanting as many amps for our bucks? This is where MPPT gets clever. In an average set up with 4 100w panels on a bright day you can produce as much as 80volts DC. However your batteries only need 12v. The controller cleverly turns the residual voltage into amps!

    So what are the benefits? The most obvious is cable thickness from the array to the charge controller. Instead of needing to handle up to 40amps on a 4 panel set up the wiring only needs to handle 10amps (I recommend using AWG10 however as it matches the panels wire leads.) From the MPPT controller to the batteries of course you need a lot thicker wire, but this run can be very short if you place the controller near the batteries. The other benefit is less loss in shading conditions. If one panel is shaded then only the voltage drops but you would still have the other panels producing voltage to the controller to produce amperage.

    panel set up from design to installation.
    The beauty of modern panels is that they come in flexible options, some able to bend by up to 240 degrees! So boats Biminis and hard tops suddenly become a very good mounting point.

    How to mount.
    Hard top mounting is pretty straightforward. Most panels come with toggle holes in the them so you can easily bolt through. Canopy Biminis are a little more complex but with a good sewing machine or canvass shop easy to work with.

    To mount on the canvass, first obtain the sizes of the panel and work out how many you can get on top. Most boats will support 3-4 panels. To attach to a canvass the best option is to sew into the canvass following the inner edge of the panel industrial Velcro, sewing to the canvass the fabric portion of the Velcro strip, this is available on Amazon. I suggest at least 2” thick or wider. The toothed strip of Velcro is self sticky backed to the panel itself. When sewing in the Velcro I do suggest adding a 3” deep piece of canopy along the lead edge of the panel making a lip that flaps over the front of the panel acting as a wind shield to stop wind getting under the panel when at speed ripping the panel off.

    Panel wiring
    As written previous. If adopting the most optimum technology (MPPT charging) then the wiring should be in series, however please check with your panel supplier each panels maximum voltage handling capacity, cheaper panels do not handle more than 40v well. I opt for ones that can handle 600vDC. I recommend fitting to each positive output wire from the panel a reverse flow diode which often comes with a 10amp fuse built in. Solar panels when controllers shut off have a habit of shunting voltage back into themselves doing a fine job of self-destruction, the diodes stop this issue.

    Once you have all panels daisy chained in serial you will be left with of course a plus and minus lead from the panel. Using either pre made cables from Amazon or making your own (make sure 10awg) you can now feed the wire down to where you have placed the charge controller. My suggestion is as close to the battery bank as possible. Wiring to the controller is easy, the controllers are well labelled. NOTE – DO NOT plug in the positive line to the panels until you have completed all wiring! Follow controller manufacturers instruction for setting up controller! Can be a little shocking if you don’t do this! Solar has no off button other than darkness.

    What size controller to use?
    My suggestion is to ask the manufacturer or supplier. Tell them how you are wiring the panels and how many, they can determine the potential output. I always use 40amp controllers for 4 x 100 panels, however 60amp is optimum and gives lots of room for upgrading. Most good controllers will not produce more than they are rated to.

    Choice of storage (Batteries)
    My optimum choice is 4 x 6volt deep cycle batteries. When wired in series/ parallel configuration you get the best storage capacity and higher battery life.

    Wiring from controller to batteries.
    The importance here is to match controller output to wiring capability. A 40amp controller typically allows for 8AWG cable. It is imperative you put an inline fuse in between the battery and controller that matches the controller output. If the controller comes with a battery monitoring thermometer, follow instructions for installation.

    My choice of supplier for panels is Renogy, they are a bit more pricey but offer the best support and product reliability. For charge controllers my preferred MPPT controller is EPever. For supplies…Amazon.

    Good luck with your own installation and feel free to contact me if you have any questions. And on a final note, if you have any concerns doing anything yourself seek professional electricians help! Even solar can harm or worse!
     
    Todd320 and JC3 like this.
  2. GnrlPatton

    GnrlPatton Active Member GOLD Sponsor

    278
    Jul 12, 2010
    Maple Valley, WA
    Current: 1998 370 Express Cruiser
    Sold:1988 230 Weekender
    Twin Cat 3116T
    GREAT writeup!

    I originally installed mine with a PWM charge controller, but I think I'm convinced I will redo it with an MPPT controller instead. I have 2x 100W panels, so the rewiring will be pretty straight forward to switch from parallel to series, and I used all 10 gauge wire everywhere (panel > controller > batteries) so that shouldn't be an issue.

    For the reverse flow diode, are you thinking something like this, installed off of each panel? https://www.amazon.com/uxcell-Anti-...ords=reverse+flow+diode&qid=1569364598&sr=8-8

    Thanks for putting this detailed info out there.
    Kevin
     
    HallOfDreams likes this.
  3. HallOfDreams

    HallOfDreams Member

    37
    Sep 11, 2019
    2003 (2004 face lift) Searay 340 8.1L Mag. Outdrive.
    Mercruiser 8.1L 496 mag
    Hey Kevin
    Yes exactly that. I think these diodes are panel life savers. You should notice a difference in MPPT. Maybe more noticeable as sun rises and falls or in part shade. I got 28 amps from 4 x 100w panels, I would of got more but controller was a 30 amp unit.
     
  4. GnrlPatton

    GnrlPatton Active Member GOLD Sponsor

    278
    Jul 12, 2010
    Maple Valley, WA
    Current: 1998 370 Express Cruiser
    Sold:1988 230 Weekender
    Twin Cat 3116T
    Nice, thanks for the reply. To be clear, I should put one on each panels' positive lead, correct?
     
  5. HallOfDreams

    HallOfDreams Member

    37
    Sep 11, 2019
    2003 (2004 face lift) Searay 340 8.1L Mag. Outdrive.
    Mercruiser 8.1L 496 mag
    Yes otherwise you can get voltage flowing back to the other one.
     
  6. GnrlPatton

    GnrlPatton Active Member GOLD Sponsor

    278
    Jul 12, 2010
    Maple Valley, WA
    Current: 1998 370 Express Cruiser
    Sold:1988 230 Weekender
    Twin Cat 3116T
    Thought so, thanks again!
     
    HallOfDreams likes this.
  7. pyro

    pyro Member

    78
    Dec 4, 2018
    2008 Sundancer 290
    Twin 5.0L MPI w/ Bravo III
    One thing I did not see addressed is practical output. Any experience you can share with practical output on a sunny vs cloudy day. I expect the panel wattage to be exaggerated and only true under ideal conditions. Almost everything works against you: clouds, angle of sun, angle of panel, panel degradation, night time. Any measurements you can share would be helpful vs the "rated" power of your panels.

    I've been looking at Victron Energy MPPT 100/20 controller mostly for their excellent statistics tracking via smartphone app over Bluetooth.

    I am on a mooring and routinely have dead batteries (replaced batteries this year), mostly due to having the fridge run while we are out and not having enough time to charge on engine power and occasional charges on transient dock or generator. I would like to be able to run fridge for 2-3 days over the weekend. Ideally all the time, but likely requires too much solar area for me. Fridge draws 4A while on.

    I also believe its a good idea to have a solar disconnect switch for times when you are connected to shore power and want normal battery charger to handle charging. The voltage coming from the panels will trick the battery charger and may not charge the battery.
     
  8. HallOfDreams

    HallOfDreams Member

    37
    Sep 11, 2019
    2003 (2004 face lift) Searay 340 8.1L Mag. Outdrive.
    Mercruiser 8.1L 496 mag
    When using 4 x 100W panels in full sun using MPPT charging out off hook with fridge going and lights we could get as much as 28 amps, however the controller was under rated at 30amps so was restricting flow. On partial shade the amps (dependant on battery requirements) were around 8-14amps on peak draw. Even on full shade days we can get a trickle charge of 2-4amp/hr

    The importance of using MPPT controllers and wiring in series is that of one or two panels are in shade the overall voltage is only reduced by those panels so the controller "tracks" the optimum input voltage to generate the most efficient charging amps output.

    I have been off hook for 5 days on solar only with two fridges and lights, plus vacuflush and never ran my 4 x 6V deep cycles down. if you have 3-4 days of bad weather then there maybe some exceptions.

    Here is an awesome answer all thread about running solar with shore power.
    https://roadslesstraveled.us/charging-rv-marine-batteries-solar-power-shore-power/
     
  9. Boat Guy

    Boat Guy Well-Known Member

    Nice write-up...

    Do you see any improvements in solar cells coming out soon? Any picts?
     
  10. HallOfDreams

    HallOfDreams Member

    37
    Sep 11, 2019
    2003 (2004 face lift) Searay 340 8.1L Mag. Outdrive.
    Mercruiser 8.1L 496 mag
    Things are always improving, right now from what I see it’s all quite stable, I think we have peaked for now at least. Flexible solar is the big new thing. I am looking at three different suppliers.

    I am doing a new install next spring so will document it with pics.
     
  11. pyro

    pyro Member

    78
    Dec 4, 2018
    2008 Sundancer 290
    Twin 5.0L MPI w/ Bravo III
    One other comment from reading some other material. It seems that partially shaded panels kill the overall output by very significant amount (50-75%). I plan on mounting 2 around a radar unit, and expect some partial shading, so sounds like parallel outputs would be better, as the shade would only affect 50% of the panels. But that's if the voltage stays high enough to turn on the controller since solar panel voltage needs to be > 5V above battery. But I'll obviously wire in a way that's easy to convert back and forth from parallel/series. What is the practical voltage on a overcast day?

    Going to do some measure some physical dimensions this weekend, and hopefully order some stuff to play around with. Probably won't have a complete installation on the boat until next season.

    Also what are the flex panel supplier you are looking at? Seems Sunpower makes the most efficient flex cells. They also sell panels. So it seems like them, or another supplier that use their cells: AllPower, RichSolar.
     
  12. HallOfDreams

    HallOfDreams Member

    37
    Sep 11, 2019
    2003 (2004 face lift) Searay 340 8.1L Mag. Outdrive.
    Mercruiser 8.1L 496 mag
    My first reply had errors in it which would have confused, I did not read the question wholly, sorry about that.

    So in regards to shading and series using MPPT (there is zero reason to use PWM in my opinion) if you have just two panels and one is in shade yes there is the risk of the output being effected. However if you have four panels then unless you have three in shade your output will be either equal or greater than all in parallel. Small system run happily on parallel equally as well using MPPT. But require higher input cable rating.

    My preferred design is 4 panels in series/ parallel. Two connected in series as two units then combined at junction to parallel to the controller. This alleviates shading issues.

    Sun power are great but with a caveat, they’re maximum system voltage states only 45v so the maximum series you can run is 3 panels, where as others are as high as 600v. Now is this due to sun power being realistic or due to their higher coefficient panels? I have used sunpower, one warped and stopped outputting. They also do not have built in diodes. Although others don’t also.

    Choices!
     
  13. HallOfDreams

    HallOfDreams Member

    37
    Sep 11, 2019
    2003 (2004 face lift) Searay 340 8.1L Mag. Outdrive.
    Mercruiser 8.1L 496 mag
    One other point about Sun power is their customer service is non existent and their suppliers or to be fair the one I dealt with had no clue about solar installations, they ended up asking me and I wrote a blog entry for them.
     

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