<font size=2 face="sans-serif">Hi:</font>
<br>
<br><font size=2 face="sans-serif">With the rapid increase in the number
of new installs and installers, the question of determining the lowest
Voc for a system which uses PWM or MPPT charge controllers has come up
more often recently.</font>
<br>
<br><font size=2 face="sans-serif">I did a slide for it in our training,</font>
<br>
<br><font size=2 face="sans-serif">a. PWM and MPPT charge controllers cannot
boost the incoming voltage. The input voltage always has to higher
than the desired charging output voltage.</font>
<br><font size=2 face="sans-serif">b. Charge controllers have a loss in
the range of 2-4%, depending on array voltage, battery voltage, charging
current, temperature etc.</font>
<br><font size=2 face="sans-serif">c. The charge controller loss will cause
a voltage drop from input to output which will be proportional to the loss
percentage.</font>
<br><font size=2 face="sans-serif">d. Additional losses will be present
due to system wiring, terminations, etc.</font>
<br><font size=2 face="sans-serif">e. The total system loss will typically
be in the range of 4 -6 %, depending on the particulars of the design and
operating conditions such as temperature, sun intensity etc.</font>
<br><font size=2 face="sans-serif">f. The lowest possible Vmp of any module
is approximately 75% to 90% of the highest possible Voc for virtually all
modules depending on module type and whole bunch of other environmental
and operating variables.</font>
<br>
<br>
<br><img src=cid:_1_0CC284F40CC1A078005C5BCE88257E57>
<br>
<br>
<br><font size=2 face="sans-serif">In other words, by the time you go through
the math, the Voc of typical PWM or MPPT systems needs to be in the range
of 1.3 X the highest desired charging voltage, (1.3X equalize voltage if
that is to be used, 1.3X bulk if that's the highest desired).</font>
<br>
<br><font size=2 face="sans-serif">If you don't have enough margin, then
the effect is that the module/array will still provide charging current,
but it will forced to operate at a voltage somewhere between Voc and Vmp.
It will therefore produce a reduced amount of charging current less
than Imp and possibly approaching zero if the module/array is asked to
operate at or very near Voc. </font>
<br>
<br><font size=2 face="sans-serif">Marginal design along with the guaranteed
variable nature of sun intensity and ambient temperature throughout the
year, very likely can result in a system which will provide a charging
current, but wont be able to quite reach bulk voltage and that of course
is not a good thing.</font>
<br>
<br><font size=2 face="sans-serif">Whatever the cause, you need more Voc.</font>
<br>
<br><font size=2 face="sans-serif">JARMO<br>
</font><font size=3 color=#008000>_____________________________________________________________________________________</font><font size=3>
<br>
</font><font size=1 face="Arial"><b><br>
Jarmo Venalainen</b> | </font><font size=1 color=#008000 face="Arial"><b>
Schneider Electric </b></font><font size=1 face="Arial"><b> | Xantrex
Brand</b> | <b>CANADA</b> | <b>Sales Application
Engineer</b> <b><br>
Phone:</b> +604-422-2528 | <b>Tech Support:</b> 800-670-0707
| <b>Mobile:</b> +604-505-0291 <b><br>
Email:</b> </font><a href="mailto:jarmo.venalainen@schneider-electric.com"><font size=1 color=blue face="Arial"><u>jarmo.venalainen@schneider-electric.com</u></font></a><font size=1 face="Arial">
| <b>Site:</b></font><a href=http://www.xantrex.com/ target=_blank><font size=1 color=blue face="Arial"><u>
www.Xantrex.com</u></font></a><font size=1 face="Arial"> |
<b>Address:</b> 3700 Gilmore Way, Burnaby, BC V5G4M1 <br>
</font>
<table>
<tr>
<td colspan=4><a href=http://www.xantrexrebate.com/ target=_blank><img src=cid:_1_0CBC56F00CBC531C005C5BCE88257E57 width=1 height=1></a>
<tr>
<td><a href=http://www.xantrex.com/ target=_blank><img src=cid:_1_0CBC5DC00CBC59EC005C5BCE88257E57></a>
<td><a href=https://www.facebook.com/Xantrex target=_blank><img src=cid:_1_0CBC655C0CBC615C005C5BCE88257E57></a>
<td><a href=https://twitter.com/Xantrex target=_blank><img src=cid:_1_0CBC6CF80CBC68F8005C5BCE88257E57></a>
<td><a href=https://twitter.com/Xantrex target=_blank><img src=cid:_1_0CBC74940CBC7094005C5BCE88257E57></a></table>
<br>
<br><font size=1 color=#00a000 face="Arial"><br>
*** Please consider the environment before printing this e-mail</font><font size=3><br>
</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">From:</font>
<td><font size=1 face="sans-serif">Luke Christy <sgsrenewables@gmail.com></font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">To:</font>
<td><font size=1 face="sans-serif">"re-wrenches@lists.re-wrenches.org"
<re-wrenches@lists.re-wrenches.org>, </font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Date:</font>
<td><font size=1 face="sans-serif">05/31/2015 10:55 AM</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Subject:</font>
<td><font size=1 face="sans-serif">[RE-wrenches] Voltage Degradation with
Uni-Solar laminate</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Sent by:</font>
<td><font size=1 face="sans-serif">"RE-wrenches" <re-wrenches-bounces@lists.re-wrenches.org></font></table>
<br>
<hr noshade>
<br>
<br>
<br><tt><font size=2>Hello Off-Grid Wrenches,<br>
<br>
I recently made a periodic maintenance visit to a residential off-grid
system I take care of here in Southern CO, and discovered an interesting
problem. <br>
<br>
This system has an array of 48x Uni-Solar PVL-68 laminate modules applied
directly to standing-seam metal roofing. <br>
<br>
The data logging on the controller (Outback MX-60) indicated that the system
was having trouble completing a charge cycle and going to float. Initially
I assumed was due to heavy electrical use by the occupants (renters). After
a little checking, I noticed that the module string voltage was only about
0.5V above the battery voltage! <br>
This was a cool late morning, with full sun, and the array was charging
almost 2kW at 54.5V. The module strings were running at 55V. I've noticed
the module voltage being lower than I'd like before, but it has never been
this low. I suspect this is the real reason the system hasn't been able
to complete a charge cycle.<br>
<br>
By removing the loads I was able to get an open-circuit voltage of 71V,
but that still seems pretty low. <br>
<br>
Has anyone else experienced a voltage degradation issue with the Uni-Solar
laminate? What was the expected annual voltage degradation for this technology?
<br>
<br>
These modules do have some age on them. The system was installed about
15 years ago (by a competent installer who is now retired). The system
was installed before MPPT controllers were common, so I assume the modules
are wired in strings of 4 for 48V nominal. <br>
<br>
Any experiences or opinions are appreciated.<br>
Thanks in advance. <br>
<br>
-Luke<br>
<br>
<br>
Luke Christy<br>
<br>
NABCEP Certified PV Installation Professional™: Certification #031409-25
<br>
NABCEP Certified Solar Heating Installer™: Certification #ST032611-03
<br>
CoSEIA Certified PV Installer <br>
<br>
Solar Gain Services, LLC<br>
PO Box 531<br>
Monte Vista, CO. 81144<br>
SGSRenewables@Gmail.com<br>
719.588.3044<br>
</font></tt><a href=www.sgsrenewables.com><tt><font size=2>www.sgsrenewables.com</font></tt></a><tt><font size=2><br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
_______________________________________________<br>
List sponsored by Redwood Alliance<br>
<br>
List Address: RE-wrenches@lists.re-wrenches.org<br>
<br>
Change listserver email address & settings:<br>
</font></tt><a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org"><tt><font size=2>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</font></tt></a><tt><font size=2><br>
<br>
List-Archive: </font></tt><a href="http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html"><tt><font size=2>http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html</font></tt></a><tt><font size=2><br>
<br>
List rules & etiquette:<br>
</font></tt><a href="www.re-wrenches.org/etiquette.htm"><tt><font size=2>www.re-wrenches.org/etiquette.htm</font></tt></a><tt><font size=2><br>
<br>
Check out or update participant bios:<br>
</font></tt><a href="www.members.re-wrenches.org"><tt><font size=2>www.members.re-wrenches.org</font></tt></a><tt><font size=2><br>
<br>
______________________________________________________________________<br>
This email has been scanned by the Symantec Email Security.cloud service.<br>
______________________________________________________________________<br>
</font></tt>
<br>
<br>