Solar Panel Install Questions

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Christy Leigh

Christy Leigh

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Jul 27, 2004
27
Nauticat 331 Wickford RI
I recently bought a Kyocera 140w panel and a 20 amp Blue Sky controller. Hopefully the larger than needed controller (for now I may add another panel later) will not negate the value of the MPPT because the panel (7a) is so small ??
I've been looking through old posts and my Kyocera info sheet also says nothing about the Ground to Earth connection in a "boat install". So is it not needed ? or must it be separately wired to the engine block ?
I've seen MaineSails posts on using smaller wire outside and then going to larger and Maine also says the controller should be as close to the battery bank as possible. So hopefully at least I have a handle on the wiring - after I get the round trip run length / gauge needed to keep the total resistance down for a low drop.

Thanks,
 
T

tommays

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Oct 2, 2006
1,517
Jboat J24 commack
I cant really see the earth ground being needed as I would think it comes into play on large home installs were the panels and connected in series to make high voltages and the voltage level could get in the hazard range ?
 
Bill Roosa

Bill Roosa

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Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
grounds are important for corrosion. WM has a great grounding page on west adviser that talks to the 5 types of grounding that boat wiring needs to address. The grounding wire on the panel is not the current return ground and serves to keep the mounting and case at 0 volts to (hopefully in a marine environment) keep it from rusting.
 
Bill Roosa

Bill Roosa

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Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
I'm thinking that lightning protection would be my major concern with a "metal frame attached to a plastic boat"
 
centerline

centerline

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Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
if you have any idea that you may add another panel later, seriously consider installing the proper size wiring for it now.
then when its time to install more watts, its plug and play.

it saves time and money to do it once and the 4awg wire can be found on at a very reasonable price:D
 
RAD

RAD

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Jun 3, 2004
2,330
Catalina 30 Bay Shore, N.Y.
centerline said:
if you have any idea that you may add another panel later, seriously consider installing the proper size wiring for it now.
then when its time to install more watts, its plug and play.

it saves time and money to do it once and the 4awg wire can be found on at a very reasonable price:D
Click to expand
Why would you run a # 4 awg wire for a panel that only produces 8 amps and if you added 2 more panels your at less than than 30 amps so a # 10 would cover all bases
 
centerline

centerline

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Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
RAD said:
Why would you run a # 4 awg wire for a panel that only produces 8 amps and if you added 2 more panels your at less than than 30 amps so a # 10 would cover all bases
Click to expand

10ga wont cover all bases, and probably not the primary base.
it depends on the length of the wire run... and 2 panels at 280 watts of power is too much for a 10ga wire.
a 10ga wire will carry 8amps about 12 feet with about a 2% drop.... if you are installing solar and the option is there, use a bigger wire and save as much of the amperage as you can for the batteries.
its a waste of time and money and power to install a wire thats too small, as the amperage lost thru the wiring can be fairly substantial,
and in addition to the panel itself becoming less efficient as it heats up, an undersized wire will also lose more power as it heats up trying to carry the load as well as the heat of the day warming it....

my run was 30ft from the panel on the rear of the boat to the controller near the batteries. I sized it for two 140w panels and 4ga is nearly perfect for maintaining a drop of 2% or less.
if you can mount the panels closer, a 6ga would work.... the goal when installing a solar panel is to get power from it, so getting the entire system to produce maximum efficiency at all times should be a priority.
 
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walt

walt

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Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
small point to be made..

Solar panels are nearly "constant current" even over temperature. It is the maximum power point voltage that varies with temperature and it is also a voltage loss caused by the parasitic resistance of the wire (not a current loss).

So if you have an MPPT type controller where it takes advantage of the delivered voltage from the solar panel, both temperature and wire loss result in less output power.

But if you have a cheaper PWM type controller (typically used on smaller panels), these don’t take advantage of the higher voltage on the panel, they just short the panel to the battery voltage.

So with the PWM type of controller, temperature does very little to the current delivered from the panel. Also, as long as there was some excess voltage to begin with (usually the case), parasitic voltage loss in the cabling also usually doesn’t matter. Using a heavy gauge wire is not so important (except between the controller and the battery).

PPM controllers don’t get you as much power to begin compared to MPPT but then are much more tolerant to panel heat and wire runs.

FYI, there was a thread on this forum when Centerline chose the 4 gauge.. He likely made a good choice since he is using a MPPT type controller.
 
centerline

centerline

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Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
Christy Leigh said:
after I get the round trip run length / gauge needed to keep the total resistance down for a low drop.
Click to expand
if you use a wire run/amps calculator from a quality source that deals with solar panels, they almost always take into consideration that you will have a wire running both directions... it will usually say somewhere on the page. double check it and make sure so there is no mistakes made in the sizing of the wire.:)
 
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