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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">Blue Sky has 15 and 30 amp, 12 and 24 volt charge controllers that are each independently MPPT that can be networked to their controller to communicate and charge
a single large battery bank. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">Jeff Irish<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">Hudson Solar<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"> re-wrenches-bounces@lists.re-wrenches.org [mailto:re-wrenches-bounces@lists.re-wrenches.org]
<b>On Behalf Of </b>Allan Sindelar<br>
<b>Sent:</b> Thursday, October 11, 2012 1:04 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> [RE-wrenches] Fwd: Charge control question<o:p></o:p></span></p>
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<p class="MsoNormal">Wrenches,<br>
I'm posting this for Carl Bickford, prof emeritus of the renewable energy training program at San Juan College in Farmington, New Mexico. I'll forward your responses to him.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I have a very interesting and talented friend who is rebuilding a blue-water sailboat for a round-the-world trip. He is well versed in solar and is trying to use a relatively large
array to charge a big battery bank that will be used for propulsion as well as general electrical. The propulsion system will be backed up with a propane generator he is building himself out of a Toyota truck engine.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">As you can imagine, there is no place on a sailboat where shading isn’t a problem. He and I were wondering if there were products out there that could MPPT either individual modules,
or small groups of them for 12 V battery charging. I have seen such things for the inputs of grid-tied inverters, but nothing yet for off-grid. The other choice is to go with many small MPPT charge controllers like the ones from Solar Converters.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Any advice you can offer?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Take care,<br>
Carl <br>
<br>
<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Carl Bickford<br>
Professor of Engineering and Renewable Energy<br>
San Juan College<br>
4601 College Blvd.<br>
Farmington, NM 87402<br>
505-566-3503<br>
<a href="mailto:bickfordc@sanjuancollege.edu">bickfordc@sanjuancollege.edu</a><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <br>
I offered the suggestion below. Certainly open to other and better ideas.<br>
Allan<br>
<br>
<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I have not encountered this situation, so I have no advice from experience. At 12V, it's hardly an issue as it is with high voltage parallel strings, where a few shaded cells can
cause a whole string to drop out of the inverter's MPPT. At most, a shaded cell weakens the output of that module. And since it's charging batteries, there's a greater amount of head room.<br>
<br>
I would suggest looking into Blue Sky Energy's "i" series - smaller MPPT controllers that can be networked. We seldom use them, as our residential applications are different. But you could put a controller on a group of modules and network several together.
One advantage, I think (you'd want to check this) is that Blue Sky's MPPT algorithm is analog, unlike Outback and others: on the old Solar Boost series, the MPPT boost was set with a trim pot to a particular voltage above battery voltage; the target is to
set it to where the boost was greatest. You could set this boost slightly lower than peak, and output just a little below MPP. That way the overall output would be minimally reduced, and a modest amount of shading would not cause the shaded module to drop
below collective MPP as readily.<o:p></o:p></p>
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<p class="MsoNormal"><br>
<b>Allan Sindelar</b><br>
<span style="font-size:10.0pt"><a href="mailto:Allan@positiveenergysolar.com"><span style="color:#000099">Allan@positiveenergysolar.com</span></a></span><br>
<span style="font-size:10.0pt">NABCEP Certified Photovoltaic Installer<br>
NABCEP Certified Technical Sales Professional<br>
New Mexico EE98J Journeyman Electrician<br>
Founder and Chief Technology Officer<br>
<b>Positive Energy, Inc.</b><br>
3209 Richards Lane (note new address)<br>
Santa Fe, New Mexico 87507<br>
<b>505 424-1112</b><br>
<a href="http://www.positiveenergysolar.com/" target="_blank">www.positiveenergysolar.com</a></span>
<o:p></o:p></p>
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