Wednesday, October 8, 2014

Re: [Electric Boats] Solar panels on the boat deck: what are safe voltage level?

 

Nice Capt. Mike. I have been looking for a way to have a removable bimuni that is a solar array. This looks good. New spring project. Thanks for posting that.
Richard




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"Mike biankablog@verizon.net [electricboats]" <electricboats@yahoogroups.com> wrote:
 

I just added a Renogy 100 watt bendable panel into my 12 volt house solar array. At four pounds it is four times lighter and smaller than the 75 watt Siemens panels I bought over a decade ago. Not sure if they will hold up as well and I'd be leery to walk on it. But, I'm impressed with it so far. Gave a nice bump up in energy collection and easily movable compared to the rigid panels:

Capt. Mike
http://biankablog.blogspot.com



On Monday, October 6, 2014 10:15 AM, "Bendik Vignes bendik.vignes@yahoo.com [electricboats]" <electricboats@yahoogroups.com> wrote:


 
Thanks for your reply and comments Kevin!
One comment on voltage: I undestand that charging voltage is different from system voltage (battery voltage). The motor I am planning to use is a 120V (might work fine on 96V). But I want to keep the voltage level on the boat´s deck as low as possible (higher voltage in the "machine room" is ok - there are no kids down there:) 
Regards Bendik

2014-10-06 15:35 GMT+02:00 pembertonkevin@gmail.com [electricboats] <electricboats@yahoogroups.com>:
 
Hello Bendik,

Charging voltage is not system voltage. The cables that come out of the panel
have connectors that are both water tight and safe around water and people. A
48 volt system will have anywhere from about 70 volts to over 100 volts from
the panel but that is after they have been hooked up in series to produce it.
This will depend on the controller. MPPT controllers are the best bet.

My system consists of 4 panels producing 1120 watts at peak bright full sun
day. On the water using reflection from the water this could be higher on some
days. The panels produce 49volts open circuit and the cheap MPPT controller I
imported converts the voltage to a 24 volt system.

Because the controller input voltage is the most important voltage of the
system (No matter what voltage you choose) consider shopping for the
controller first, then find suitable panels for it.

My crystaline panels cover an area of roughly 8 square meters, maybe a little
more. Morph panels will require more space.

My panels weigh in at over 50 lbs per panel. This makes using them as a shade
difficult on a boat but if the bank is low in the boat may work.

Any shade on even one panel connected to a single controller will reduce
output considerably. For this reason I do not suggest deck mount but rather as
a shade over the cockpit, or davits. I have used small panels on my canoe for
shade and to extend the range. I would never be caught in a storm with the
configuration but if prudent would work for others.

Final point.

Controllers are cheaper in the 24/12 volt variety than for higher voltages at
your wattage. Higher wattage and the 48 volt systems shine. The lower voltage
panels are more per watt. A controller that works on 12/24 volts will not
produce 12 volts with panels that are above about 28 volts ( this is a gray
area). The controller for 24 volts will handle about twice the watts as it
will if used on 12 volts.

Considering the above information I would likely choose a 24 volt system for
the size of 1000 watts. Because of space limitations on boats I would only
consider crystaline panels for a system of 1000 watts. I would keep an eye on
the kids and keep them off the panels. If working with a sail boat I would make
sure no shackles ever found their way to the panel surface. I would set chores
for the kids to take care of those panels so they would take pride in them.
This could be the morning dew removal with a squeegee, and have them see the
increase from the panel from their effort, and give them a slap on the back.

All in all every watt you do not need to pull from the bank will save you the
resistance the bank charges in interest. May the sun and wind always be at
your back.

Kevin Pemberton

On Tuesday, September 30, 2014 09:33:17 AM you wrote:
> Hi!
> What is safe voltage level for solar panels mounted in the "traffic zone" on
> a boat deck? ...Kids playing around with wet hands...
>
>
> 12-20V?
> Or higher?
>
>
> I am planning a ~1kW array to power electric propulsion (120V motor)
>
>
> What are your opinions/experiences?
>
>
> Bendik




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