Walt,<div><br></div><div>I would look at using the Blue Sky 6024H in 36v input, 24v output mode. The physical dimensions are identical, and it can use the same temperature sensor (if the systems don't currently have temp sense, btw, add it. Absolutely). I still believe Rick's controllers are some of the most efficient products available on the market, which really comes into play on small unmonitored systems. If you can't get the original seller of the systems to pony up and take back the old controllers, then I would recommend selling them on consignment for the client on systems where the arrays can be chosen appropriately.</div>
<div><br></div><div>As far as the batteries, most AGMs have low self discharge characteristics, but who knows how long they've been in transit and in storage. I would strongly advise to place them on a charge at the shop and load testing them, before putting them in service. If they're really a 12v battery sitting at 5v, they may be only qualified for door stop duty now.</div>
<div><br clear="all">Phil Undercuffler<br>Conergy<br>--------<br><br><br>
<br><br><div class="gmail_quote">On Tue, Jun 30, 2009 at 2:26 AM, Walt Ratterman <span dir="ltr"><<a href="mailto:wratterman@sunenergypower.com">wratterman@sunenergypower.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div lang="EN-US" link="blue" vlink="purple">
<div>
<p><span style="color:#1F497D">Hello all,</span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">Thanks to all of your responses,
and particularly Rick’s confirmation of the appropriate ranges for the SB50, it
has become clear that these panels can not be made to work with the SB50, and
that the SB50 was the wrong choice for these pre-fabricated systems, or perhaps
better phrased, the panels were the wrong choice for the controller. Actually,
it is probably more accurate that the panels were the wrong choice because
their characteristics severely limit the possible options of what to do next.</span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">I would like your input on what
you think should be done here.</span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">Nine systems were purchased from
Earthwalk. One has been deployed for four months. A second unit is being
deployed now. This leaves seven in the warehouse. (And we wont even get into
the fact that we have AGM batteries here instead of the advertised GEL
batteries, and the voltage is so low they might not even work……I will deal with
that separately…..)</span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">While it is clear that the
panels do not match up with the controller, it is not clear why they are still
working (other than the heat and dirt) and if they will continue to work. </span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">One solution would be to just
leave everything alone and tell them what they should do if the system(s)
fail. In some cases, this might be the right action to take. But in this
case, I think the folks who sold the prefabricated unit should be held
accountable, and provide a system that is designed to work properly. The
schools paid good money for this equipment and they should at least have a
running start at success, which is difficult to come by in this part of the
world on a good day.</span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">So – when we tell the schools to
insist that the system be fixed, what do you think we should tell them?</span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">Due to the characteristics of the
panel (not being either 12V or 24V nominal) they need a MPPT controller. I
suppose we could tell them to change to a controller that will accept the
output of the panel. This would be either Outback, Midnite Solar, or possibly
the new Morningstar 15A controller. Any suggestions?</span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">The other route would be to have
them change the panels, and keep the prefabricated system as it is. Rick:
what would you recommend the best voltage / current combination to replicate
the need for a 440 to 500 watt peak array output with the SB50? </span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">Given the relative cost of the
panels versus the controller, the manufacturer may likely decide to switch the
controllers, but it is not as easy as it sounds. If either the Outback or
Midnite controllers are used, they will not fit into the small space the
cabinet allowed for the SB50. But I will deal with that another way. (We will
just build an all new cabinet here in Senegal).</span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">So – any ideas or thoughts I
have missed are welcome!!</span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">Thanks so much for all of the
great feedback. I think, like most of us, every day is a learning experience,
even if we think we have done this 100 times before. </span></p>
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">Take care,</span></p><div class="im">
<p><span style="color:#1F497D"> </span></p>
<p><span style="color:#1F497D">Walt</span></p>
<p><span style="color:#1F497D"> </span></p>
<div>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<p><b><span style="font-size:10.0pt">From:</span></b><span style="font-size:10.0pt"> Rick Cullen - Blue
Sky Energy, Inc. [mailto:<a href="mailto:rick@blueskyenergyinc.com" target="_blank">rick@blueskyenergyinc.com</a>] <br>
<b>Sent:</b> Monday, June 29, 2009 10:14 AM<br>
<b>To:</b> <a href="mailto:wratterman@sunenergypower.com" target="_blank">wratterman@sunenergypower.com</a>; 'RE-wrenches'<br>
<b>Subject:</b> RE: [RE-wrenches] Solar Boost Controller in Senegal</span></p>
</div>
</div>
<p> </p>
<p><span style="font-size:10.0pt">Hello
Everyone,</span><span style="font-size:12.0pt;font-family:"Times New Roman","serif""></span></p>
<p><span style="font-size:12.0pt;font-family:"Times New Roman","serif""> </span></p>
<p><span style="font-size:10.0pt">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""></span></p>
<p><span style="font-size:12.0pt;font-family:"Times New Roman","serif""> </span></p>
<p><span style="font-size:10.0pt">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""></span></p>
<p><span style="font-size:12.0pt;font-family:"Times New Roman","serif""> </span></p>
<p><span style="font-size:10.0pt">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""></span></p>
<p><span style="font-size:12.0pt;font-family:"Times New Roman","serif""> </span></p>
<p><span style="font-size:10.0pt">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""></span></p>
<p><span style="font-size:12.0pt;font-family:"Times New Roman","serif""> </span></p>
<p><span style="font-size:10.0pt">Regards,</span><span style="font-size:12.0pt;font-family:"Times New Roman","serif""> <br>
</span><span style="font-size:10.0pt">Richard
A. Cullen</span><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">
<br>
</span><span style="font-size:10.0pt">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">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">fax
760-597-1731</span><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">
<br>
<a href="mailto:rick@blueskyenergyinc.com" target="_blank"><span style="font-size:10.0pt">rick@blueskyenergyinc.com</span></a> <br>
<a href="http://www.blueskyenergyinc.com/" target="_blank"><span style="font-size:10.0pt">www.blueskyenergyinc.com</span></a> <br>
</span><span style="font-size:12.0pt"> </span><span style="font-size:12.0pt;font-family:"Times New Roman","serif""> </span></p>
<p><span style="font-size:12.0pt;font-family:"Times New Roman","serif""> </span></p>
<div 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 style="margin-bottom:12.0pt"><b><span style="font-size:10.0pt">From:</span></b><span style="font-size:10.0pt"> <a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>] <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""></span></p>
</div><p>Hello,</p><div><div></div><div class="h5">
<p> </p>
<p>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.</p>
<p> </p>
<p>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.</p>
<p> </p>
<p>Charge Controller is a Solar Boost 50. </p>
<p> </p>
<p>Batteries are Dekka AGM – two strings of 250AH, 12V
batteries. (four batteries total).</p>
<p> </p>
<p>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.</p>
<p> </p>
<p>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. </p>
<p> </p>
<p>But…..isnt this a dangerous way to design a system?
(it will get cooler here ….)</p>
<p> </p>
<p>Or am I missing something? </p>
<p> </p>
<p>What would be the appropriate application here….</p>
<p> </p>
<p>Sorry, I cant do a lot of internet research from here –
limited download capability on the satellite….</p>
<p> </p>
<p>Thanks!!</p>
<p> </p>
<p>Walt</p>
<p> </p>
<p><b><span style="font-size:10.0pt">Walt
Ratterman</span></b></p>
<p><b><span style="font-size:10.0pt">SunEnergy
Power International</span></b><b><span style="font-size:10.0pt;font-family:"Times New Roman","serif""></span></b></p>
<p><b><span style="font-size:10.0pt;font-family:"Times New Roman","serif""> </span></b></p>
<p><span style="font-size:8.0pt">11
Laurel Lane South Washougal, WA 98671</span></p>
<p><span style="font-size:8.0pt">(360)-837-3680
▪ fax (360)-837-1315 ▪ Skype
Walt-Mobile</span></p>
<p><span style="font-size:8.0pt"><a href="mailto:wratterman@SunEPI.org" target="_blank">wratterman@SunEPI.org</a> </span><span style="font-size:10.0pt"> </span><span style="font-size:8.0pt">▪ <a href="http://www.sunepi.org/" target="_blank">www.SunEPI.org</a></span></p>
<p> </p>
<p> </p>
<p><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><br>
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