Myles,
Can you, (or anyone) explain the whole thing about the "positive" ground on the Sun Power panels. I get the part about the solar cells essentially being mounted in the panel assembly up side down, I just can't wrap my mind around how it works at the battery and boat chassis level. Understanding this kind of stuff is a problem for me sometimes as a mechanical engineer in an electrical/electronic world so please make any explanations ot the most fundamental level possible if you can.
I've heard for lower voltages you can just let it float, especially with the flexible panels that don't have a metallic frame so I just ignored it on my 12V dinghy project that I used several flexible SunPower panels on. (They were impressive btw and seem to be holding up well to some pretty substantial abuse that I put them through this year). But I also read somewhere that there is a big problem with performance of the individual cells in the panel if you don't provide this positive ground for systems above 24V. And this positive grounding methodology is not compatible with standard inverters and charge controllers, requiring special considerations for these components. ie. a different model specifically made for this application.
Any light you can shed is much appreciated.
Capt. Carter
shipofimagination.com
On Monday, June 1, 2015 8:50 AM, "cirejay@hotmail.com [electricboats]" <electricboats@yahoogroups.com> wrote:
Myles,
Help me out. The way you present it, it's a 'no brainer' Given that space can be an overriding factor on a boat, 20% efficiency vs.10-12% may win out, even with the 100% premium.
As I have been comparing panels though, it doesn't necessarily seem to work out that way. It looks more like 16% efficiency for $1.40 per watt vs. 20% for $2.00 per watt.
Assuming that flexible panels would not necessarily be a plus in my installation, an that panel configuration either way, is there another reason to go with the sun power panels?
Thanks for your always helpful inputs,
eric SV Meander
---In electricboats@yahoogroups.com, <matwete@...> wrote :
Hey Cal-
Good to hear you haven't given up on e-boating. J
For 40amps and 48v, you're looking at about 2kw.
To get the most power per area and to keep things light, you'd want to not skimp on your panels---ie. don't buy 10-12% efficient, $1/watt panels that are framed and heavy.
Rather, you'd want to invest in the 20% efficient, unhoused SunPower flexible arrays which run about $2/watt and available any day, online and on ebay. For $4k, you can get your 2kw.
For 2kw, at 20% efficiency, you need at least 10sq-meters of solar cells.
And practically, at our latitude, you'd still not get 2kw, but let's say this did tell the whole story.
You'd need a bimini area approx. 6.5ft x 16ft to get your 2kw. Do you have that much roof space? How about half of that?
Here's a 135watt Sunpower panel:
Pick up 16 of those and for less than $5k you're cooking with solar.
How deep are your pockets?
-Myles
On Monday, June 1, 2015 8:50 AM, "cirejay@hotmail.com [electricboats]" <electricboats@yahoogroups.com> wrote:
Myles,
Help me out. The way you present it, it's a 'no brainer' Given that space can be an overriding factor on a boat, 20% efficiency vs.10-12% may win out, even with the 100% premium.
As I have been comparing panels though, it doesn't necessarily seem to work out that way. It looks more like 16% efficiency for $1.40 per watt vs. 20% for $2.00 per watt.
Assuming that flexible panels would not necessarily be a plus in my installation, an that panel configuration either way, is there another reason to go with the sun power panels?
Thanks for your always helpful inputs,
eric SV Meander
---In electricboats@yahoogroups.com, <matwete@...> wrote :
Hey Cal-
Good to hear you haven't given up on e-boating. J
For 40amps and 48v, you're looking at about 2kw.
To get the most power per area and to keep things light, you'd want to not skimp on your panels---ie. don't buy 10-12% efficient, $1/watt panels that are framed and heavy.
Rather, you'd want to invest in the 20% efficient, unhoused SunPower flexible arrays which run about $2/watt and available any day, online and on ebay. For $4k, you can get your 2kw.
For 2kw, at 20% efficiency, you need at least 10sq-meters of solar cells.
And practically, at our latitude, you'd still not get 2kw, but let's say this did tell the whole story.
You'd need a bimini area approx. 6.5ft x 16ft to get your 2kw. Do you have that much roof space? How about half of that?
Here's a 135watt Sunpower panel:
Pick up 16 of those and for less than $5k you're cooking with solar.
How deep are your pockets?
-Myles
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Posted by: Carter Quillen <twowheelinguy@yahoo.com>
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