<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;">Kirpal, <br></span></font></p><p class="MsoNormal"><br><font face="Arial" size="2"><span style="font-size: 10pt;"></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;">You’ve
got it summed up pretty well, although I would add that you need to use RS485
cards and cabling between the SBs and the SI Master to get regulated charging –
the comm. allows the SI to send a handshake to the SB, telling the SB to go into
“off grid” mode and accept wider voltage and frequency swings whenever the grid
is not present. </span></font><font face="Arial" size="2"><span style="font-size: 10pt;">Kent sums up this control mechanism very succinctly below.</span></font><font face="Arial" size="2"><span style="font-size: 10pt;"> <br>
</span></font></p><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;"><br></span></font></p><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;">The biggest challenge when mixing brands is dealing with the 300 second
timeout </span></font><font face="Arial" size="2"><span style="font-size: 10pt;">after grid
disturbance</span></font><font face="Arial" size="2"><span style="font-size: 10pt;"> (what I call 5 minute PWM) make for less than ideal system
operation. There needs to be a better way to regulate power than
kicking the string inverter offline.</span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;"> </span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;">Imagine, say, a 7kW array pumping energy into the home
on a beautiful sunny day. The grid
goes down, but the </span></font><font face="Arial" size="2"><span style="font-size: 10pt;">battery based inverter (</span></font><font face="Arial" size="2"><span style="font-size: 10pt;">BB) picks up the slack and the </span></font><font face="Arial" size="2"><span style="font-size: 10pt;">grid-tied batteryless inverter (</span></font><font face="Arial" size="2"><span style="font-size: 10pt;">GT) stays online. Home is
drawing less power than the array’s output (~6kW worth), and the batteries are
full. Battery voltage hits the regulation
voltage, and the BB inverter (or the voltage controlled switch) activates a
relay to open the circuit to the GT inverter, effecting a blackout on that
circuit. Suddenly the BB inverter and the battery bank is hit with the full 6kW
of load. The batteries are a little undersized because that was the easiest
portion of the system to cut costs on, and they’re a little old and dried out
from years of sitting in an uncooled garage, so their voltage sags
under the load. The voltage controlled switch senses the drop, and closes the
relay to the GT. However, the GT has to stay offline for another 299 seconds
and the battery voltage continues to fall…..</span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;"> </span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;">I’ve
been worried about just this scenario for some time, especially as systems age.
Therefore, I’ve been suggesting to anyone interested in using mixed brands of
inverters (or those who don’t want to use RS485 communications with SB/SI
combos) that they strongly consider installing a diversion load and controller
capable of absorbing at least the majority of the expected surplus energy. A
blackout relay can be used as a secondary control mechanism. I think that this
is going to provide the most reliable operation, ultimately.</span></font><font size="2"><span style="font-size: 10pt;"></span></font></p>
<p style="color: rgb(0, 0, 0);" class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;"> </span></font></p><p class="MsoNormal"><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="ProgId" content="Word.Document"><meta name="Generator" content="Microsoft Word 11"><meta name="Originator" content="Microsoft Word 11"><link style="color: rgb(0, 0, 0);" rel="File-List" href="file:///C:%5CDOCUME%7E1%5Cphu%5CLOCALS%7E1%5CTemp%5Cmsohtml1%5C01%5Cclip_filelist.xml"><style>
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</style><span style="font-size: 10pt; font-family: Arial; color: navy;"><span style="color: rgb(0, 0, 0);">To answer the question about number of inverters, the SMA 5048U supports parallel
operation of up to 4 inverters on a single phase system, up to 4 inverters on a
split-phase system, or three inverters on a 3-phase system -- all connected to one battery bank. The PV can come through any number of SB inverters, but they would all be connected to the same protected load panel served by the SI. This is one "cluster." The rule of thumb John Berdner passed along years ago was up to 2kW of PV for every 1kW of SI. If you can break the load into multiple clusters, the system can be any size -- you just run multiple clusters side by side independently. If the loads can't be separated, then you need to look at using the Multi-cluster box, but that's not yet Listed or even technically "available" in the US. But if the job is </span><i style="color: rgb(0, 0, 0);">really </i><span style="color: rgb(0, 0, 0);">that big, you're playing in a whole 'nother ballpark. Definitely not the job to take on for your first battery based project.</span></span></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;"> </span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;"> </span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;">Phil Undercuffler</span></font><font size="2"><span style="font-size: 10pt;"></span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;">Director, Battery-based and
Off-grid</span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;">Distribution Sales Group</span></font><font face="Times New Roman" size="2"><span style="font-size: 10pt; font-family: 'Times New Roman';"></span></font></p>
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<p class="MsoNormal"><b><font color="blue" face="Arial" size="2"><span style="font-weight: bold; font-size: 10pt; color: blue;">Our World Is Full of
Energy</span></font></b><font size="2"><span style="font-size: 10pt;"></span></font></p>
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Camino </span></font><font size="2"><span style="font-size: 10pt;" lang="PT-BR">Carlos Rey Suite 103</span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;" lang="PT-BR">Santa Fe, NM 87507</span></font></p>
<p class="MsoNormal"><font face="Arial" size="3"><span style="font-size: 12pt;"><a title="mailto:p.undercuffler@conergy.us" href="mailto:p.undercuffler@conergy.us"><font title="mailto:p.undercuffler@conergy.us" size="2"><span title="mailto:p.undercuffler@conergy.us" style="font-size: 10pt;" lang="PT-BR">p.undercuffler@conergy.us</span></font></a></span></font><font size="2"><span style="font-size: 10pt;" lang="PT-BR"></span></font></p>
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<p class="MsoNormal"><font face="Arial" size="2"><span style="font-size: 10pt;"> </span></font></p><br clear="all">Phil Undercuffler<br><br><br><br><br>
<br><br><div class="gmail_quote">On Tue, Oct 20, 2009 at 1:38 PM, <span dir="ltr"><<a href="mailto:re-wrenches-request@lists.re-wrenches.org">re-wrenches-request@lists.re-wrenches.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
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<br>Today's Topics:<br>
<br>
1. Re: AC Coupled Re-visited (Walt Ratterman)<br>
<br><br>---------- Forwarded message ----------<br>From: "Walt Ratterman" <<a href="mailto:wratterman@sunenergypower.com">wratterman@sunenergypower.com</a>><br>To: <<a href="mailto:glenn.burt@glbcc.com">glenn.burt@glbcc.com</a>>, "'RE-wrenches'" <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>><br>
Date: Tue, 20 Oct 2009 12:37:04 -0700<br>Subject: Re: [RE-wrenches] AC Coupled Re-visited<br>
<div bgcolor="white" link="blue" vlink="purple" lang="EN-US">
<div>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">Glenn:</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">This is correct on the battery bank separation.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">You don’t split out the battery banks until you reach a “cluster”.
For example, one three phase setup is a cluster. If you have two, three-phase
setups – you have two clusters – and two battery banks.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">And…I think if you check through the charging parameters, you
will find that the ratio of 10 to 1 as you have below is very conservative for
PVkw versus battery Ah. We have gone with 10KW PV vs 1800 Ah with no problem.
I think maybe what they may mean is that the 10 to 1 ratio is for what you
intend to CHARGE in the battery bank. So – if you are planning on a 50% DOD
every day, then maybe the 10 to 1 would work well, for that 50%.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">Walt</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<div>
<div style="border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span style="font-size: 10pt; color: windowtext;">From:</span></b><span style="font-size: 10pt; color: windowtext;"> <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>Glenn
Burt<br>
<b>Sent:</b> Tuesday, October 20, 2009 12:14 PM<br>
<b>To:</b> 'RE-wrenches'<br>
<b>Subject:</b> Re: [RE-wrenches] AC Coupled Re-visited</span></p>
</div>
</div>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">SMA recently told me that the recommended Ah of the battery bank
is related to the amount of PV and connected inverters.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">They recommended a 500Ah bank with a 5kW PV SB, and a 600Ah bank
with a 6kW PV SB.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">100Ah to 10,000Ah are the supported capacities.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">I don’t believe you need to have a separate battery bank with
two SI’s. I have been told they can share one. One SI is programmed as the
master & of course they are data commed together so they can talk.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">-Glenn</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<div>
<div style="border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span style="font-size: 10pt; color: windowtext;">From:</span></b><span style="font-size: 10pt; color: windowtext;"> <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>Mark
Frye<br>
<b>Sent:</b> Tuesday, October 20, 2009 2:42 PM<br>
<b>To:</b> 'RE-wrenches'<br>
<b>Subject:</b> Re: [RE-wrenches] AC Coupled Re-visited</span></p>
</div>
</div>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span style="font-size: 10pt; color: blue;">Thanks Kent. And so I understand more clearly, in the case of 2 SIs
as you describe, each SI has it's own battery bank, and the solar would be
split between the two.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span style="font-size: 10pt; color: blue;">Considering the charging capacity of the SI, what would you say is
the largest battery bank size for each SI to insure an effective "C"
value?</span></p>
<p class="MsoNormal"> <br>
<span style="font-size: 10pt;">Mark Frye</span>
<br>
<span style="font-size: 10pt;">Berkeley Solar
Electric Systems</span> <br>
<span style="font-size: 10pt;">303 Redbud Way</span>
<br>
<span style="font-size: 10pt;">Nevada
City, CA 95959</span> <br>
<span style="font-size: 10pt;">(530) 401-8024</span>
<br>
<a href="http://www.berkeleysolar.com/" target="_blank"><span style="font-size: 10pt;">www.berkeleysolar.com</span></a><span style="font-size: 10pt;"> </span> </p>
<div>
<p class="MsoNormal"> </p>
</div>
<p class="MsoNormal"> </p>
<div class="MsoNormal" style="text-align: center;" align="center">
<hr align="center" width="100%" size="2">
</div>
<p class="MsoNormal" style="margin-bottom: 12pt;"><b><span style="font-size: 10pt;">From:</span></b><span style="font-size: 10pt;"> <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>Kent
Osterberg<br>
<b>Sent:</b> Tuesday, October 20, 2009 11:10 AM<br>
<b>To:</b> <a href="mailto:glenn.burt@glbcc.com" target="_blank">glenn.burt@glbcc.com</a>; RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] AC Coupled Re-visited</span></p>
<p class="MsoNormal">In off-grid mode the Sunny Island uses frequency shift power
control to reduce the output of the Sunny Boy inverters and thereby regulate
the battery voltage. At some frequency shift (+1, or 2, or 3 Hz, I'm not
sure) the output of the SB is reduced by 100%. It's proportional so that
1/2 as much frequency shift gives a 50% reduction in the SB output. To
keep clocks accurate, the Sunny Island later shifts the frequency a negative
amount, but the SB inverters ignore that. For a grid backup system, a
RS-485 cable is required so the Sunny Island can activate (or deactivate) the
frequency shift power control capability of the SB.<br>
<br>
You need to stack two SI inverters to get 240-vac, but that will allow you to
have a 10-kW of grid backup power with up to 12-kW of solar. If you need
more, you can stack four of SI inverters.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar, Inc.<br>
<br>
<br>
Glenn Burt wrote: </p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">Our installations of Sunny Islands (SI) with Sunny Boys (SB)
have always used the recommended RS-485 communications between all units
involved. This with reprogramming the SB’s to be able to switch to off-grid mode
per the SI instructions allows a more integrated system.</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">We have had problems with the OB PSX-240 and stepping up the 120
to 240 for the crit load panel (where the SB’s connect) when the site has slightly
high AC voltages. The SB pushes the existing ACV higher, then it goes out of UL
spec & disconnects. Also the SB is now sensitive to imbalance on L1 &
L2 because of the neutral sensing – we had a customer where the SB was
disconnecting due to this as well…</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">I thought the freq shifting was to allow other non-SMA inverters
to be controlled when batteries were full?</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">Where is the SMA rep on this list?</span></p>
<p class="MsoNormal"><span style="font-size: 11pt; color: rgb(31, 73, 125);">-Glenn</span></p>
<div style="border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p class="MsoNormal"><b><span style="font-size: 10pt;">From:</span></b><span style="font-size: 10pt;"> <a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>]
<b>On Behalf Of </b>Kirpal Khalsa<br>
<b>Sent:</b> Tuesday, October 20, 2009 12:05 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] AC Coupled Re-visited</span></p>
</div>
<p class="MsoNormal">Greetings......it is my understanding that the Sunny Island
coupled with Sunny Boys is able to taper charge in an AC coupled system as the
2 inverters are able to communicate with each other and the Sunny Island alters
the frequency input of the Sunny Boys and lowers the total output of the Sunny
Boys to match the needs of the battery bank....this is SMA's method of not
using their "charger"....they simply alter the amount of available AC
input into the AC to DC converter present in the Sunny Island.....This logic is
what encouraged me to select SMA's for an AC coupled design rather than mixing
brands of battery-less and battery based inverters.....in a mixed brand
scenario there is no communication other than an on/off command so no
regulation is available.....My understanding may be flawed--please correct me
if so....<br>
Another way for mixed brands to AC couple and provide some charge
"control" would be to have an AC dumpload on the AC input side of the
battery based inverter to suck up some of the excess power from the GT
inverters so not as much power is available for battery charging.....This
dumpload would be voltage based and in a mixed brand system would add more
relays to the mix...in many cases there may not be that many auxillary outputs
available to connect relays to.....<br>
I would like to see more GT inverter companies make compatible battery based
inverters......One idea is for micro inverters to be paired with the battery
based inverters and when less power was needed to facilitate a taper charge one
solar panel at a time could be switched off......effectively providing a
smaller available charge current to help with the taper charging.....<br>
<br>
-- <br>
Sunny Regards,<br>
Kirpal Khalsa<br>
NABCEP Certified Solar PV Installer<br>
Renewable Energy Systems<br>
<a href="http://www.oregonsolarworks.com" target="_blank">www.oregonsolarworks.com</a><br>
541-218-0201 m<br>
541-592-3958 o</p>
<div>
<p class="MsoNormal"><br>
On Tue, Oct 20, 2009 at 8:34 AM, Mick Abraham <<a href="mailto:mick@abrahamsolar.com" target="_blank">mick@abrahamsolar.com</a>> wrote:</p>
<p class="MsoNormal" style="margin-bottom: 12pt;">Hi, All~<br>
<br>
On an AC coupled system as Jeff describes, the "battery charge
circuitry" on the battery based inverter is not even participating. <br>
<br>
A straight pure sine inverter...with no charger function built in...would also
"charge" the battery if AC coupled to a SunnyBoy with no grid
available. The "charge" is just the inverter's way of dealing with
back EMF.<br>
<br>
I agree that better control over that "recharge" is an important
area; I hope somebody is working on that. It's true that the "wild card
recharge" only occurs if grid goes away but as Jeff mentions, it only
takes a few times of crummy end of charge management to ruin a nice set of
sealed batteries.<br>
<br clear="all">
Mick Abraham, Proprietor<br>
<a href="http://www.abrahamsolar.com" target="_blank">www.abrahamsolar.com</a><br>
<br>
Voice: 970-731-4675<br>
<br>
</p>
<div>
<div>
<div>
<p class="MsoNormal">On Tue, Oct 20, 2009 at 9:21 AM, Jeff Yago <<a href="mailto:jryago@netscape.com" target="_blank">jryago@netscape.com</a>>
wrote:</p>
</div>
</div>
<blockquote style="border-style: none none none solid; border-color: -moz-use-text-color -moz-use-text-color -moz-use-text-color windowtext; border-width: medium medium medium 1pt; margin: 5pt 0in 5pt 4.8pt; padding: 0in 0in 0in 6pt;">
<div>
<div>
<div>
<div>
<p class="MsoNormal"><span style="font-size: 10pt;">We have
completed several totally different AC coupled systems using different
inverters, due to large ground mounted arrays that had to be located a great
distance from inverter-battery-generator-grid BAS, which are working just fine
even with the mis-match of inverter brands. The SunnyBoy seems to not
care what its connected to or how, as it just keeps doing what it does and if a
relay cuts off its connection to the grid when the battery voltage goes high
then it just waits and re-connects when the grid is back or the battery voltage
drops.</span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size: 10pt;">What
I am bothered by is the need to custom design a power relay circuit on
each project which takes lots of fine-tuning of setpoints to get
everything to work correctly. If you have not done one the problem is
simple - when you backfeed the AC output from a remote grid-tie inverter
"through" the AC side of a battery based inverter, everything works
great and the solar AC just passes straight through the sub-panel, back
throught the battery inverter, back into the grid. However, when
the grid is down and the battery-inverter is no longer receiving (or
sending) power from the grid, for some reason I cannot begin to understand, any
AC being fed from the solar inverter goes straight into battery charging with
absolutely no limit on charge rate or charge limit, and if you do not add a
relay to dis-connect or shut-down the solar inverter you can quickly destroy a
bank of AGM batteries if there are no major system loads as it just keeps
charging and charging.</span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size: 10pt;">I
am not an electronics engineer, but if the battery is being charged by the
battery charger built into the inverter, I just do not see why the same battery
charger suddenly has no clue that the battery is being overcharged when its now
receiving AC power from a different source. I think with larger and
larger arrays being installed as module costs fall, higher DC array string
voltges to reduce wire costs, and more people worried about grid reliability,
there would be a good market niche for an inverter that can properly charge a
battery bank regardless of which way the AC power comes into the charger
section. Whats the problem?</span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size: 10pt;">Jeff
Yago</span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size: 10pt;">DTI
Solar</span></p>
</div>
<p class="MsoNormal"><span style="font-size: 10pt;"><br>
</span></p>
<div class="MsoNormal" style="text-align: center;" align="center"><span style="font-size: 10pt;">
<hr align="center" width="100%" size="2">
</span></div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
<p class="MsoNormal"> </p>
</div>
</div>
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