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Wrenches,<br>
Here's one of those threads to save if you expect to do large
multi-inverter battery-based systems. This is a thread from last
August, with recent updates.<br>
Bottom Line: in a large system with Sunny Islands, use a 1,000A/50mV
shunt, not a 1000A/100mV shunt. It's counterintuitive.<br>
Allan<br>
<br>
On Tue, Jul 31, 2012 at 6:37 AM, Allan Sindelar <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:allan@positiveenergysolar.com" target="_blank">allan@positiveenergysolar.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> Wrenches,<br>
What are you using when you need a shunt larger than the
standard 500A/50mV?<br>
<br>
The application: four Sunny Islands and a Radian in a large
grid-tie with backup system. Total current flow through B- is
rated 850A (using 125A SI DC breakers) or 1,050A (using 175A DC
breakers) on a single large battery bank. Given uncertain
continuous amperage, I should use a 1,000A shunt or even a
1,200A shunt, as Deltec recommends never exceeding 67% of a
shunt's current rating for long. Deltec makes both; see <a
moz-do-not-send="true"
href="http://www.deltecco.com/MKC-DC.html" target="_blank">http://www.deltecco.com/MKC-DC.html</a>.
The shunt will be installed inside of a Nottagutter-8, with a
Midnite shunt bus on each side. The shunt will be used with the
Sunny Island master to control overall SOC and charging
parameters; there's no plan for a Tri-Metric in this system, as
a Sunny Webbox will handle online monitoring per the customer's
wishes.<br>
<br>
The 1,000 and 1,200A series MKC Deltec shunts are the same
physical dimensions as the common 500A/50mV units. However, the
larger units are still 50mV. Ralph Heisey of Bogart Engineering,
in his "Information on Shunts" reference article (<a
moz-do-not-send="true"
href="http://www.deltecco.com/MKC-DC.html" target="_blank">http://www.deltecco.com/MKC-DC.html</a>),
tells us to match the ratio of voltage drop to current - that
is, just as a 500A shunt drops 50mV, a larger shunt with 1,000A
flowing through it should drop 100mV. But all of the larger
Deltec shunts are still rated 50mV.<br>
<br>
Who has done this and resolved the issue? What shunt did you
use?<br>
<br>
Thank you,<br>
Allan <br>
<span><font color="#888888">
<div>-- <br>
<font face="Times New Roman, Times, serif"><b>Allan
Sindelar</b></font><br>
<small><a moz-do-not-send="true"
href="mailto:Allan@positiveenergysolar.com"
target="_blank"><font face="Times New Roman, Times,
serif" color="#000099"><u>Allan@positiveenergysolar.com</u></font></a></small><font
face="Times New Roman, Times, serif"><br>
<span style="font-size:10pt">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><a moz-do-not-send="true" href="tel:505%20424-1112"
value="+15054241112" target="_blank">505 424-1112</a></b><br>
<a moz-do-not-send="true"
href="http://www.positiveenergysolar.com/"
target="_blank"><u>www.positiveenergysolar.com</u></a></span></font>
<br>
<span style="font-size:10pt"> </span> </div>
</font></span></div>
</blockquote>
<br>
<table class="moz-email-headers-table" border="0" cellpadding="0"
cellspacing="0">
<tbody>
<tr>
<th nowrap="nowrap" valign="BASELINE" align="RIGHT">Date: </th>
<td>Tue, 31 Jul 2012 14:11:06 -0700</td>
</tr>
<tr>
<th nowrap="nowrap" valign="BASELINE" align="RIGHT">From: </th>
<td>Bogart Engineering <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:bogart@bogartengineering.com"><bogart@bogartengineering.com></a></td>
</tr>
</tbody>
</table>
<br>
Hi Allan et al:
<div><br>
</div>
Here are some comments about shunts, if you are interested--<br>
<div><br>
</div>
<div>Twenty years ago I called Deltec and talked to them about amp
ratings for shunts-- at that time they said that they never tested
them themselves-- they just made them "like other manufacturers
did", then assumed the ratings they were OK. My impression is
that the "67% rule" came out of a hat, not out of actual
measurement.</div>
<div> </div>
<div>The basic rule is that the shunt material (plates between the
brass blocks) is and alloy called manganin, (designed for very
stable resistance under changing temperature.) should not exceed
140 degrees Celsius (not Fahrenheit) . Incidentally, there is
surprising disagreement on what this temp should be-- I trusted
most a German company that sold the manginin material.) I
actually measured some shunts and their temperature rise and found
the 67% rule to be VERY approximate.</div>
<div> </div>
<div>The temperature rise for one given shunt is going to be
proportional to the square of the current, so the temp rise at
100Amps is 30 degrees, for 200 amps it would be 120 degrees. The
bottom line for this is that it is only when the currents get
really high could you seriously overheat them. Some may remember
some so called "200% rated" and even "300% rated" shunts in "the
old days" which were hardly different in size from the 100% rated
ones. Don't know what they were smoking when they came up with
these. </div>
<div><br>
</div>
<div>So if you really want to know how much a shunt can handle,
measure the temperature rise right in the center of the plates,
with a steady 200Amps. You can pretty much assume that the temp
rise above that will be proportional to the square of the current.
You don't want the temp in the center of the plates to go above
140 C. </div>
<div><br>
</div>
<div>Frankly, maybe you guys know better, but I can't imagine ever
going above 500 amps in any system-- maybe, if systems are really
getting that big, people should be considering going to 96V
systems if they have power requirements that high. I would be
really surprised if any shunt rated at 1000A could really go that
high, continuously, without overheating. (But I could be wrong!)</div>
<div><br>
</div>
<div>Lastly, if there is really a demand, we could modify the
TriMetric so it would work for 1000A/50mV shunts-- this would at
least reduce the shunt heating to 50% compared to 1000A/100mV
shunts--and possibly even more. Another possibility for very large
systems could be to provide a cooling fan for the shunt, which
could come on when the amps get high. That should would increase
the rating a good bit. You could use it instead of a 500A/50mV
shunt with a TriMetric (or other similar amp measuring device) but
you get readings 1/2 of the true reading-- so would need to
multiply it by 2 to get actual reading.</div>
<div><br>
</div>
<div>Incidentally we sell some "1000A/100mV" Deltec shunts that
we've never measured the capability of. My GUESS is that it might
do 600-700 A-- since the much smaller 500A/50mV shunts are OK to
about 400 A. 1000A only for a very short time. It's about 7
inches long. </div>
<div><br>
</div>
<div>Here's a picture (Warning-- it is very high resolution- and may
take forever to load unless you have a fast internet connection)</div>
<div><br>
</div>
<div><a moz-do-not-send="true"
href="http://www.bogartengineering.com/sites/default/files/images/high-res/1000A-100mv_shunt.jpg">http://www.bogartengineering.com/sites/default/files/images/high-res/1000A-100mv_shunt.jpg</a></div>
<div><br>
</div>
<div>Yours truly,</div>
<div>Ralph Hiesey, Bogart Engineering</div>
<div><br>
</div>
<span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span>
<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";color:windowtext">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">
Allan Sindelar [<a class="moz-txt-link-freetext" href="mailto:allan@positiveenergysolar.com">mailto:allan@positiveenergysolar.com</a>] <br>
<b>Sent:</b> Tuesday, August 21, 2012 11:50 AM<br>
<o:p></o:p></span></p>
</div>
</div>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt">This request for
a product development will come up with four or more Sunny
Islands. With the newest 6000W model, it may even be advisable
with a pair of inverters, or three in 3-phase. SMA tells me that
the SI programming allows selection of a shunt ampacity of
100-1000 amps in 100A increments. However, the only mV choices
are 50mV or 60mV. So for this application, we need to work with
a 1000A/50mV shunt.<br>
<br>
Ralph Heisey at Bogart Engineering has researched shunts enough
to determine that Deltec shunts can't handle their rated
ampacity continuously; they'll overheat. They can handle about
2/3 or a bit less than this. So bigger is definitely better in
this case, especially if the SI units can charge at their full
100A-per-inverter capacity.<br>
<br>
Deltec makes one shunt in the correct size, that includes a
phenolic base. It's the MKC-1000-50, type MSC 102, on web page <a
href="http://www.deltecco.com/MKC-DC.html">http://www.deltecco.com/MKC-DC.html</a>.
It's a larger version of the 2-bolt, side-terminal Kelvin screw
model that we're familiar with. Deltec's price for this is
$33.60 with a $50 minimum order.<br>
</p>
<p class="MsoNormal" style="margin-bottom:12.0pt">--------
Original Message --------
</p>
<table class="moz-email-headers-table" border="0" cellpadding="0"
cellspacing="0">
<tbody>
<tr>
<th nowrap="nowrap" valign="BASELINE" align="RIGHT">Subject:
</th>
<td>FW: Battery Shunt</td>
</tr>
<tr>
<th nowrap="nowrap" valign="BASELINE" align="RIGHT">Date: </th>
<td>Tue, 26 Mar 2013 18:42:02 -0600</td>
</tr>
<tr>
<th nowrap="nowrap" valign="BASELINE" align="RIGHT">To: </th>
<td>'Tom Carpenter' <a class="moz-txt-link-rfc2396E" href="mailto:tom@midnitesolar.com"><tom@midnitesolar.com></a>,
<a class="moz-txt-link-rfc2396E" href="mailto:Allan@positiveenergysolar.com"><Allan@positiveenergysolar.com></a></td>
</tr>
</tbody>
</table>
Tom,<br>
<div class="moz-text-html" lang="x-western">
<div class="WordSection1">
<p class="MsoNormal"><span style="color:#1F497D">I am just
forwarding this to you for your info, it sounds like a
100MV shunt can be used, but they do not recommend it
based on the Email below and it makes sense. Will you
update me when you get word when you can send me the 50Mv
1000Amp shunt. I can send back the one I currently have. <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"">
Dane Forsberg [<a class="moz-txt-link-freetext" href="mailto:Dane.Forsberg@sma-america.com">mailto:Dane.Forsberg@sma-america.com</a>] <br>
<b>Sent:</b> Tuesday, March 26, 2013 5:02 PM<br>
<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal">I received an email back from my
colleagues in Germany regarding the battery shunt. The
Sunny Island’s measurement range is 0-120 mV in order to
allow for peak currents (2 x 60 mV). <o:p></o:p></p>
<p class="MsoNormal">Since it may be possible that you also
see peak currents that are greater than 1000 A, they did not
recommend that you use the 100 mV / 1000 A shunt.<o:p></o:p></p>
<p class="MsoNormal">Best Regards, <o:p></o:p></p>
SMA America, LLC<o:p></o:p><br>
<b>Dane Forsberg<o:p></o:p></b><br>
<i>Senior Technical Service Specialist,<o:p></o:p></i><br>
<i>Hybrid Energy Solutions<o:p></o:p></i><br>
6020 West Oaks Blvd, Suite 300<o:p></o:p><br>
Rocklin, CA 95765 - 3714<o:p></o:p><br>
U.S.A.<o:p></o:p><br>
Service Line: +1 877 697 6283<o:p></o:p><br>
Fax: +1 916 624 2445<o:p></o:p><br>
Email: <a href="mailto:Dane.Forsberg@SMA-America.com">Dane.Forsberg@SMA-America.com</a><o:p></o:p><br>
<a href="www.SMA-America.com">www.SMA-America.com</a><o:p></o:p></div>
</div>
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