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<div class="moz-cite-prefix">Chris Freitas is my hero; that was true
wrenching, even better that his mad scientist's experiment is
still relevant 20 years later. Here's a link to the full article
I stumbled on to last night:
<a class="moz-txt-link-freetext" href="http://www.ibiblio.org/london/alternative-energy/homepower-magazine/archives/27/27p26.txt">http://www.ibiblio.org/london/alternative-energy/homepower-magazine/archives/27/27p26.txt</a><br>
Very cool that William was pulling it from his vault this morning,
too.<br>
Chris encased the batteries in concrete or safety, but apparently
nothing happened to them.<br>
Just one note Chris mentioned on the smaller breakers, they would
not see as high a fault current, since they would be wired with #6
or smaller wire. This added wire resistance would reduce the
current at the breaker. I'm not saying that we depend on that,
just that a real world short is not going to have 4/0 cables
protected by a QO breaker.<br>
Also, I found that higher amp class T fuses (601 to 1200 amps)
have an AIC of 100,000 amps DC. SO throwing some of those inline
on big systems might make sense. Now if we could just get an acid
proof fuse holder for them.<br>
I know 240.21H allows OCPDs in the battery box, but I still don't
believe the fuses and holders are listed for the corrosive
environment.<br>
<pre class="moz-signature" cols="72">R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760</pre>
On 4/9/2013 10:54 AM, <a class="moz-txt-link-abbreviated" href="mailto:toddcory@finestplanet.com">toddcory@finestplanet.com</a> wrote:<br>
</div>
<blockquote cite="mid:1365526469.330121242@webmail.finestplanet.com"
type="cite"><font face="arial" size="3">
<p style="margin:0;padding:0;">when i hear of current flows like
this i cant help but wonder is there a risk of batteries
exploding during these kinds of tests?</p>
<p style="margin:0;padding:0;"> </p>
<p style="margin:0;padding:0;">todd</p>
<p style="margin:0;padding:0;"> </p>
<p style="margin:0;padding:0;"> </p>
<p style="margin:0;padding:0;"> </p>
<p style="margin:0;padding:0;">On Tuesday, April 9, 2013 7:00am,
"William Dorsett" <a class="moz-txt-link-rfc2396E" href="mailto:wmdorsett@sbcglobal.net"><wmdorsett@sbcglobal.net></a> said:<br>
<br>
</p>
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<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">This topic comes up often enough that we ought
to mention a yellowed article in Home Power, (1992 Issue
27, pg 26). Christopher Freitas wrote <em>Overcurrent
Protection for Battery-Powered Systems </em>where he
describes experiments he did back when he was with
Ananda. He put a 2000 A Big Switch to initiate a short
(4/0 cable) between the terminals on a set of four golf
cart batteries (2 strings @ 12V). In series, he put in a
500A Shunt so he could measure current passing and
various fuses and breakers. “For comparison, we decided
to directly short the battery…the meter read 6960 amps
peak current (three seconds) …during each test the 4/0
cable lifted off the ground 4 inches into the air by the
forces generated by the extremely high current..” They
videoed the 250 A ANN buss fuses arc and smoke; the 200A
Heinemann Series AM breakers (paralleled ones that maybe
Roy mentioned) went 3 seconds without breaking and the
video showed a flash and blue smoke. </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">175A ITE breaker with 42,000 AIC “simply
tripped…but still allowed a peak current of 2960 amps</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">200A Class T Littlefuse “opened promptly with
no external signs of stress…1920 amps peak current”</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">Christopher’s recommendations: </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">“Every AE system must have overcurrent
protection able to interrupt the maximum current
available from the batteries. For most systems, the main
protection should use current limiting high AIC fuses,
such as a Class T or Class R. A disconnect switch which
allows the fuse to be safely changed should be included.
A lower cost alternative is to mount the fuse in a fuse
holder without a disconnect. Although the fuse would
always be electrically hot, it normally would not be
changed during the life of the system. The fuse holder
should be mounted outside the battery enclosure. Fuses
should not be bolted directly onto the battery terminal,
as they are not designed to handle the physical stresses
that can occur without the protection of a fuse holder.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">Fuses which have exposed elements, such as ANN
fuses, should not be used because they are not current
limiting and have only 2500 amps AIC. They also may be a
significant hazard when installed near batteries. </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">High AIC breakers, like the Heinemann Series
CF (25,000 Amps AIC @ 65VDC) can provide overcurrent
protection for individual items. They cannot be used to
protect lower AIC breakers. This eliminates their use as
a main disconnect in most systems. </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">Low AIC breakers, like the Heinemann Series AM
(5000A AIC @65 VDC) or the Square-D QO (5000A @ 125 VDC)
can be used in load distribution centers and components,
but must be protected by a current limiting fuse. Using
low-AIC breakers alone will not provide sufficient
protection with a battery system and may be a
significant hazard during short circuit situations.”</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">It won’t pull up anymore on HP’s article
search but probably Michael has a copy he could post for
those interested.<em> </em></span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">Bill Dorsett</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">Manhattan, KS</span></p>
<div>
<div style="border: none; border-top: solid #B5C4DF 1.0pt;
padding: 3.0pt 0in 0in 0in;">
<p class="MsoNormal" style="margin:0;padding:0;"><strong><span
style="font-size: 10.0pt; font-family:
"Tahoma","sans-serif"; color:
windowtext;">From:</span></strong><span
style="font-size: 10.0pt; font-family:
"Tahoma","sans-serif"; color:
windowtext;">
<a class="moz-txt-link-abbreviated" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a class="moz-txt-link-freetext" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <strong>On
Behalf Of </strong>John Berdner<br>
<strong>Sent:</strong> Monday, April 08, 2013 7:25
PM<br>
<strong>To:</strong> <a class="moz-txt-link-abbreviated" href="mailto:Allan@positiveenergysolar.com">Allan@positiveenergysolar.com</a>;
RE-wrenches<br>
<strong>Subject:</strong> Re: [RE-wrenches] Fuse
sizing in battery circuits</span></p>
</div>
</div>
<p class="MsoNormal" style="margin:0;padding:0;"> </p>
<div>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">Allan:</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">A pretty accurate retention of the Grass
Valley / Nevada County through 2000.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">You only missed the Trace to Xantrex
“acquisition” that was the start of the divorce </span><span
style="font-size: 11.0pt; font-family: Wingdings;
color: #1f497d;">J</span><span style="font-size:
11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">Class T fuses provide better protection for
battery based inverters – always been that way.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">The move to breakers was a cost reduction
issues when Trace introduced the DC-250.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">I still contend that the way the DC-250 did
it was a Code violation when used with PV in the box
(current from all sources issue) but that is history.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">For high current applications the Boltswitch
Pull outs (the ones we used in the Power Centers) came
in 100A, 200A and 400 A sizes and 1, 2, and 3 pole
versions. </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">I think they are still made today.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">Still the best way to do currents above 250
Amps.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">You can do a Eaton / GJ1P breaker up to 750
Amps but they are Spin Dee.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">As you noted you can use a single pull out
to do up to 3 battery strings.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">You make a copper “comb” to parallel
separate fused inputs to a single inverter. </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">If you have more than one inverter you can
have “back to back” fuse blocks with an H-H-H shaped
bus bar set up.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">The biggest one I recall we did was a 12 400
A battery/PV inputs going to 8 SW inverters.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">You size the copper bus bars for 1000 A /
square inch of cross section and you are good to go
(this is from the UL 508 design guide).</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<div>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">Best Regards,</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">John Berdner</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">General Manager, North America</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">SolarEdge Technologies, Inc.</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">3347 Gateway Boulevard, Fremont CA 94538
USA </span><strong><em><span style="font-size:
11.0pt; font-family:
"Calibri","sans-serif";
color: #c00000;">(*Please note of our new
address.)</span></em></strong><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"><br>
T: 510.498.3200, X 747</span></p>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;">M: 530.277.4894 </span></p>
</div>
<p class="MsoNormal" style="margin:0;padding:0;"><span
style="font-size: 11.0pt; font-family:
"Calibri","sans-serif"; color:
#1f497d;"> </span></p>
<div>
<div style="border: none; border-top: solid #B5C4DF
1.0pt; padding: 3.0pt 0in 0in 0in;">
<p class="MsoNormal" style="margin:0;padding:0;"><strong><span
style="font-size: 10.0pt; font-family:
"Tahoma","sans-serif";
color: windowtext;">From:</span></strong><span
style="font-size: 10.0pt; font-family:
"Tahoma","sans-serif"; color:
windowtext;"> <a moz-do-not-send="true"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a moz-do-not-send="true"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>]
<strong>On Behalf Of </strong>Allan Sindelar<br>
<strong>Sent:</strong> Friday, April 05, 2013 9:00
PM<br>
<strong>To:</strong> RE-wrenches<br>
<strong>Subject:</strong> Re: [RE-wrenches] Fuse
sizing in battery circuits</span></p>
</div>
</div>
<p class="MsoNormal" style="margin:0;padding:0;"> </p>
<div>
<p class="MsoNormal"
style="margin:0;padding:0;margin-bottom: 12.0pt;">William,<br>
For this I went deep into the catacombs of our
hardware file cabinet, and quickly found a 1996 spec
sheet from an Ananda Power Technologies SafeT-Block.
For the young'uns, Ananda was a quality company, the
originator of the listed Powercenter - the breaker and
terminal block hardware that is part of every
batttery-based system nowadays. Ananda became APT,
then Pulse, then part of Trace (the PC250 and PC500)
as part of a short-lived marriage followed by a messy
divorce, the results of which led, as an act of
revenge insurrection, to the introduction into the
U.S. market of the Sunny Boy and AC-coupled systems,
and the rest is even more wacky history. But I
digress, after a run-on sentence bad enough that my
high school English teacher is rolling over in her
grave...<br>
<br>
I have attached a scan of page two of the spec sheet.
In the upper left corner is a chart of current vs.
time for a Class T fuse. Once I understood this chart
I never again worried about nuisance tripping, as
whether described as fast-acting or not, Class T fuses
have an inherent surge capacity of about 2 1/2 times
their rating, and thus can handle surges.<br>
<br>
If you put them on individual battery strings, the
point is to prevent overcurrent on one string, which
is only likely to occur when either 1) a terminal is
corroded sufficiently that one string fails to carry
its share of the load or charge (we have seen this) or
2) one string fails when the batteries reach
end-of-life. When the Class T fuses blows in that
situation it has done its job.<br>
Allan</p>
<div>
<p class="MsoNormal" style="margin:0;padding:0;"><strong>Allan
Sindelar</strong><br>
<span style="font-size: 10.0pt;"><a
moz-do-not-send="true"
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>
<strong>Positive Energy, Inc.</strong><br>
3209 Richards Lane (note new address)<br>
Santa Fe, New Mexico 87507<br>
<strong>505 424-1112</strong><br>
<a moz-do-not-send="true"
href="http://www.positiveenergysolar.com/"
target="_blank">www.positiveenergysolar.com</a></span></p>
<p class="MsoNormal"
style="margin:0;padding:0;mso-margin-top-alt: auto;
margin-right: 722.25pt; mso-margin-bottom-alt:
auto;"><br>
<img moz-do-not-send="true"
src="cid:image001.png@1365526469.1842"
alt="image001.png"></p>
<p class="MsoNormal" style="margin:0;padding:0;"> </p>
</div>
<p class="MsoNormal" style="margin:0;padding:0;">On
4/5/2013 8:29 PM, William Miller wrote:</p>
</div>
<blockquote style="margin-top: 5.0pt; margin-bottom:
5.0pt;">
<p class="MsoNormal"
style="margin:0;padding:0;margin-bottom: 12.0pt;">Friends:<br>
<br>
Good topic. Some questions:<br>
<br>
1. Most manufacturer's present an installation guide
that shows one OCPD in the battery circuit and that is
in the BOS cabinet. This means the battery leads are
unprotected. Do we need an OPCD at the battery
terminals?<br>
<br>
2. Class T fuses are generally recommended for this
application. The data shows them as "fast acting."
Is this a problem? Will they act too fast and open
during normal surge loads?<br>
<br>
Thanks in advance!<br>
<br>
William Miller<br>
<br>
<br>
<br>
<br>
<br>
</p>
<p class="MsoNormal" style="margin:0;padding:0;">Troy,<br>
<br>
Overcurrent device size is matched to the conductor
size. The inverse time constant nature of an
overcurrent device can typically handle the surge
currents as long as conductor sizing has truly been
done correctly for the conductor. Circuit breakers are
preferred to fuses because they can be reset. <br>
<br>
There has been volumes written on this issue. The
constant current at lowest battery voltage should be
used, plus the ac ripple content on the battery
circuit. This is usually a much larger conductor than
your average designer will plan for. The best thing is
to look at Midnight, Outback, and Schneider and see
what size overcurrent devices they require for their
products. That will give you a good clue as to how to
size the conductor and overcurrent device.<br>
<br>
Bill.<br>
<br>
<strong>From:</strong> <a moz-do-not-send="true"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a moz-do-not-send="true"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>]
<strong>On Behalf Of </strong>Troy Harvey<br>
<strong>Sent:</strong> Friday, April 05, 2013 3:38 PM<br>
<strong>To:</strong> RE-wrenches<br>
<strong>Subject:</strong> [RE-wrenches] Fuse sizing in
battery circuits<br>
<br>
I've got a question about battery string fusing.
Typically we size the wire from the batteries to the
inverter based on continuous rating procedures (max
power/efficiency)*125%. <br>
<br>
However a 6kW inverter, can peak at 12kW for 5-10
seconds, doubling the source current. That is no big
deal for the wire, because it is a short time frame...
little heat will be generated. However, in fusing the
sub-strings, you need to account for that peak surge
current so you don't blow fuses all the time. But if
you put a 500-1000 amp fuse on a 4/0 wire, above the
max surge draw of the inverter, the wire will be
under-protected for its ampacity rating. Any thoughts
on the catch-22?</p>
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