[C320-list] Solar panels and shading

[Scott Thompson]

Tim, I am thinking of doing the same and am wondering whether you 
considered the alternative of wiring in series instead of parallel with 
an MPPT controller to bring the 24v maximum output down to proper 
charging voltage. I added one smaller solar panel a few years ago but 
installed an MPPT controller and heavier wiring to the stern to allow 
for this later upgrade. Imagine my disappointment to learn that the 
flexible panel manufacturers do not recommend series installation 
because of the shading issue and instead recommend separate wiring and a 
separate controller for the second panel. I'm guessing that the shading 
is not much of a problem on the bimini, but I'm wondering if you did any 
research to figure out which approach is better.

And to the group as a whole, are there any experts that you are aware of 
that I could consult about this question?

Scott Thompson
Surprise, #653

On 1/30/2018 2:19 PM, Timothy Woods wrote:
> Two years ago I installed two 100 watt flexible panels on my bimini and
> haven't plugged in since. I connected them in parallel with a MPPT
> controler and have no problems with shading when sailing. I'm in south
> Florida and primarily use my boat during the winter months when the sun is
> low. ( November till April.) We live full time on the boat for two to three
> months at a time. At anchor or on a mooring I tie the boom off to the side
> and get approximately 65 amp hours returned on a good day to the batteries.
> The refrigerator is the biggest draw at 35 AH per 24 hours. We also watch 2
> to 3 hours of TV and charge both cell phones.
>
> I hope this helps, Tim
>
> On Jan 30, 2018 9:22 AM, "Marek Fluder" <marekf at gmail.com> wrote:
>
>> Last summer our docks were rebuilt so we had no power for quite some time.
>> I played with a fixed 100W panel/controller that friend had sitting unused.
>> I wanted to check the feasibility of sustaining the fridge running.
>> In full sun with the panel fully perpendicular to sun rays and unobstructed
>> it was able to "pump" 6.5A at 12.7V, so roughly delivering 82W.
>> With the panel just sitting at a convenient and most optimal location on
>> the foredeck it was producing 5.5-6.0A - about 70W.
>> Any partial shade on the panel would drop the current substantially - I do
>> not remember to what level, but it was dramatic.
>> This setup was able to sustain the fridge running for a few days, but the
>> battery voltage was dropping slowly so I have determined it is not
>> sustainable in the longer run.
>> I ran this test in second half of June which has the longest days.
>> I hope this shed some practical light on this topic.
>>
>> Marek
>> #1028
>> Hamilton, ON
>>
>>
>>
>> On Tue, Jan 30, 2018 at 8:58 AM, <ptormey at 4square.net> wrote:
>>
>>> Well, I think you really do need to check with the manufacturer. They'll
>>> have guidelines.
>>>
>>> Internal to a panel the cells are wired both parallel and in series to
>>> achieve the voltage and amperage required (Power=Volts X AMPS). This also
>>> protects failed cells from blocking the output.
>>> In the old days it was common for some cells to be dead at manufacturer
>>> and still perform within spec.
>>>
>>> My own unit (Suaoki 100W 18V 12V Solar Panel Charge) is 12-18 volts with
>>> an XCSOURCE 30A 12V/24V Solar Charge Controller Solar Panel Battery
>>> Intelligent Regulator LD296
>>> Works fine on cloudy days and great on sunny days I keep it on the
>>> 'flexed' over the Dodger which is, of course, under the boom.   It
>> doesn't
>>> do any heavy lifting like refrigeration but keeps the batteries fresh.
>>> IF I wanted more power I'd parallel another 12-18 volt panel and let the
>>> regulator do its job.
>>>
>>> It's hard to express the affect of shade without a constant load, but
>> your
>>> supplier should be able to put some parameters on it.
>>>
>>> Here is a good (simple ) article on the subject
>>> http://www.mpptsolar.com/en/solar-panels-in-parallel.html
>>>
>>>
>>>
>>> Pat
>>>
>>>
>>>
>>>
>>
>> --
>> ~~~~~~~_/)~~~~~~
>>