Steve,
I will run the numbers that others have not. Polycrystaline panels that produce good numbers produce roughly 13 watts per sq. Foot. How you divide that up into amps and volts is your choice. As was stated in previous posts any shade on part of the panel reduces the output to the lowest denominator, this is dependent on panel configuration. (lowest output cell on the panel). amorphous Panels don't put out the same amount of power per sq. foot as do the Polys but will still put out well in partial shade. The reason this is so is the dye color can be made to suit. Lab discoveries show Polys that employ a bubble surfaced mylar mirror behind the cell as a backing can increase the output to close the gap between crystaline panels and Polys. to date however the polys sold by places like Harbor Freight with a surface area of roughly 9sq ft. produce a grand 45w. or 5w per sq. ft.
To fix the shade problem you could build a mylar mirror as discribed on Nielson Enterprises web site and reflect the sun onto the panel. This would take some effort on your part but may be worth the effort if you want to go green. This method would make the need to have the panels move to get best results void for all installations as well.
If you want solar to add much to your boat you will find house loads benefit from solar. If you are at anchor or dock they may give you a head start on fuel consumption at the start of a journey. Don't expect them to replace plentiful fuel however, because I know of no renewable fuel system that is up to the task without a lot of real estate.
Kevin Pemberton
On 12/31/2011 12:00 PM, Steve Dolan wrote
Actually Myles I would want to take the Solar array to the 144v batteries first if possible since the House Bank is charged from them through the 144v to 12v charger/converter. No direct connection from the Solar to the House bank. This would require at least 4 48v panels (I think), which is questionable for my Davit installation, giving me 192v with a MPPT (if they even make one this size, to control the voltage to around 164v or 13.6v per battery. These would have to be in series so I’d get only 210w (est) or 1.2 Amps correct? If so this isn’t enough to justify the system cost.
OR
Run the Solar to the House Bank (12v) with a MPPT. 3 panels at 17v each in parallel at 210w or 16 Amps? Now we are getting somewhere.
My question on sending the solar up to the 144v bank was just 1 to many drink thinking, and has been discarded along with the empties. KISS.
Steve in Solomons MD
Lagoon 410 SE
From: electricboats@yahoogroups.com [mailto: electricboats@yahoogroups.com ] On Behalf Of Myles Twete
Sent: Friday, December 30, 2011 4:49 PM
To: electricboats@yahoogroups.com
Subject: RE: [Electric Boats] Re: Ok solar experts
Steve-
It’s not clear to me what you are suggesting with the solar panels, but it sounds like you are suggesting that you would take your no. 144v solar array and apply it directly to your 12v house battery bank without reconfiguring the panels to be connected in parallel instead of series.
If that is the case, then your 144v panel array will only deliver 1/12th the rated power to the 12v battery bank compared to its being connected to the 144v bank. The panels deliver current (not power) proportional to the solar energy captured by them. The lower you clamp the voltage, the less power captured and delivered. Connecting the panels in parallel and direct connecting to the 12v bank would be better. Shading one panel would not affect the others. In series, a single panel or fraction thereof can take down the entire string’s output. But say you go with parallel panels and their Vmpp is 17v. At 12-13v battery voltage, you’d only be capturing some 65% or so of the solar energy. Incorporating a MPP tracker could boost that up above 90%, but then the cost may not justify it.
-Myles
From: electricboats@yahoogroups.com [mailto: electricboats@yahoogroups.com ] On Behalf Of Steve D
Sent: Thursday, December 29, 2011 7:54 AM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Re: Ok solar experts
Hi Damon,
A good point and one I'm questioning as far as running solar through the Propulsion bank. Yes I also have a house bank, 3 agm's at 12v 540AH.
The existing system is set up to take everything through the Propulsion (144v) bank. All charging (regen, Genset, shore) and distribution starts there. The house bank gets it's charging from a 144v to 12v (DC to DC) converter. Since this is the starting point my first thoughts would be to take the solar to that point since any excess solar power would then be sent to the House bank. The question then is with shading will the 144v bank still charge or just shut down the solar since it can't meet the 144 voltage? If this is the case it would be better to have the panels going to the 12V House bank. Another question is can I find an UP inverter from 12V to 144V. If I can than this would be much simpler. Then you also have a charger down (144v to 12v) and up (12v to 144v). I wonder what that would do to everything? It's getting to the point of I can't have it both ways it seems. The good news is if I just do solar to the House bank then a substantial load would be taken of the Propulsion bank. It's just that I think I would still have excess solar that could be added to the Propulsion bank instead of just "throwing it away".
Does any of this make sense?
Thanks,
Steve in Solomons MD
Lagoon 410 SE
> Connecting solar panels in series to get 144v will work, but shading on any
> of the panels will degrade the output of the whole series string. I have a
> friend who built a systems that charges at 12v and drives the boat at 48v.
> Afterwards, he's not convinced it's better than a DC/DC converter, but the
> idea was for charging in parallel and propulsion in series for higher
> efficiency during both.
>
> Didn't the original post mention a big 12v bank that was electrically
> connected to the traction bank? I'm not familiar with DC/DC converters, but
> if you charged the 12v, would the converter charge the traction bank?
>
> Damon
>
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