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<p class=MsoNormal><span style='color:#1F497D'>Hello Rick and everyone,<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Rick – this is VERY helpful
information. <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Let me digest this for a few
minutes and get back to you with some more input, and maybe some questions
relative to what is going on. We are going to see some more units in the morning.
(There are 9 total, but only a couple of them are in operation so far….)<br>
<br>
<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Thanks,<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Walt<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Rick Cullen - Blue
Sky Energy, Inc. [mailto:rick@blueskyenergyinc.com] <br>
<b>Sent:</b> Monday, June 29, 2009 10:14 AM<br>
<b>To:</b> wratterman@sunenergypower.com; 'RE-wrenches'<br>
<b>Subject:</b> RE: [RE-wrenches] Solar Boost Controller in Senegal<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Hello
Everyone,</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>The
SB50's maximum input voltage spec it 57VDC. This should be considered an
absolute maximum above which the controller will be damaged in a manner not
covered by warranty. Our recommendation is to not apply a total Voc at STC
of more than 57V/1.25= 45.6V. There are transient voltage protection diodes on
both battery and PV inputs on ALL Solar Boost charge controllers.
These are not "tell tail" indicators but real protection devices
designed/selected to protect down stream electronics from transient voltage
damage resulting from ESD, lightning, etc. On the PV side of the SB50 the
protection diodes will begin to clip at about 58-60V. They can eat a 1
millisecond 3000W transient without damage, but will burn up if they receive
more than about 10W continuously. These two diodes are located right behind the
PV terminals. </span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>In
the application described below I would expect the SB50 to be damaged. What
typically happens with excess over voltage is the diodes fail short, and
then clamp PV voltage low and protect the down stream electronics. If PV
current is sufficiently high the diodes will burn open and the SB50 may
continue to operate since down stream devices have somewhat higher voltage
withstand capability, or it may suffer catastrophic damage.</span><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Why
these systems continue to operate must be due to actual Voc not getting high
enough long enough to cause catastrophic damage. If the controllers were
to not switch to Float (unloading the PV's), the brief Voc sample as part of
MPPT may not have burned up the diodes and they are successfully eating the excess
voltage transients which would seem to occur during the Voc sample. It may
also be that the modules are so hot that their actual Voc & Vmp are
low enough that when PV voltage is clamped to 60V by the SB50's protection
diodes insufficient power is delivered at 60V to burn up the diodes...</span><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Needless
to say, this is a situation that need to be corrected. Technical Bulletin
#100214 available on our web site describes proper voltage, current and power
sizing for all Solar Boost charge controllers.</span><span style='font-size:
12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Regards,</span><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <br>
</span><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Richard
A. Cullen</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>
<br>
</span><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Blue Sky
Energy, Inc.</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>
<br>
</span><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>760-597-1642
x102</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>
<br>
</span><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>fax
760-597-1731</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>
<br>
<a href="mailto:rick@blueskyenergyinc.com"><span style='font-size:10.0pt;
font-family:"Arial","sans-serif"'>rick@blueskyenergyinc.com</span></a> <br>
<a href="http://www.blueskyenergyinc.com/"><span style='font-size:10.0pt;
font-family:"Arial","sans-serif"'>www.blueskyenergyinc.com</span></a> <br>
</span><span style='font-size:12.0pt;font-family:"Arial","sans-serif"'> </span><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p>
<div class=MsoNormal align=center style='text-align:center'><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'>
<hr size=2 width="100%" align=center>
</span></div>
<p class=MsoNormal style='margin-bottom:12.0pt'><b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Walt
Ratterman<br>
<b>Sent:</b> Friday, June 26, 2009 3:22 PM<br>
<b>To:</b> 'RE-wrenches'<br>
<b>Subject:</b> [RE-wrenches] Solar Boost Controller in Senegal</span><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal>Hello,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I am in a very remote part of Senegal, (near the
Guinea and Mali borders…) and I have come across some prefabricated “plug
and play” American made systems installed for educational institutions.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The systems use two Sharp panels that are 220Watts, 33.6
Voc, 29.2 Vmp, wired in series, using #10AWG home run wire from the panels back
to the charge controller.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Charge Controller is a Solar Boost 50. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Batteries are Dekka AGM – two strings of 250AH, 12V
batteries. (four batteries total).<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>My specific question is about the controller. This is
a 24V in / 24V out charge controller with MPPT. I have not used this
before, so I am not familiar with the details of operation.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The data sheet that I downloaded says that the maximum open
circuit voltage is 57 VDC. But, this system is hitting the charge
controller with two panels of 33.6 VDC wired in series for 73.2VDC. So,
why is the controller not fried, or what am I seeing wrong here. I
suppose with the panel temperature being elevated maybe 35 degrees above 25
degrees and a resulting 17.5% loss, coupled with some voltage drop, the system
may actually be seeing less than the 57 volts. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>But…..isnt this a dangerous way to design a system?
(it will get cooler here ….)<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Or am I missing something? <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>What would be the appropriate application here….<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Sorry, I cant do a lot of internet research from here –
limited download capability on the satellite….<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thanks!!<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Walt<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Walt
Ratterman<o:p></o:p></span></b></p>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>SunEnergy
Power International</span></b><b><span style='font-size:10.0pt;font-family:
"Times New Roman","serif"'><o:p></o:p></span></b></p>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></b></p>
<p class=MsoNormal><span style='font-size:8.0pt;font-family:"Arial","sans-serif"'>11
Laurel Lane South Washougal, WA 98671<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:8.0pt;font-family:"Arial","sans-serif"'>(360)-837-3680
▪ fax (360)-837-1315 ▪ Skype
Walt-Mobile<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:8.0pt;font-family:"Arial","sans-serif"'><a
href="mailto:wratterman@SunEPI.org">wratterman@SunEPI.org</a> </span><span
style='font-size:10.0pt;font-family:"Arial","sans-serif"'> </span><span
style='font-size:8.0pt;font-family:"Arial","sans-serif"'>▪ <a
href="http://www.sunepi.org/">www.SunEPI.org</a><o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><br>
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